Tektronix KEITHLEY 2520 User Manual

Pulsed laser diode test system

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Model 2520 Pulsed Laser Diode

Test System

User's Manual

2520-900-01 Rev. D / January 2020

*P2520-900-01D*

2520-900-01D

Table of Contents

Summary of Contents for Tektronix KEITHLEY 2520

Page 1 www.tek.com/keithley Model 2520 Pulsed Laser Diode Test System User's Manual 2520-900-01 Rev. D / January 2020 *P2520-900-01D* 2520-900-01D...
Page 2 Model 2520 Pulsed Laser Diode Test System User’s Manual © 2019, Keithley Instruments, LLC Cleveland, Ohio, U.S.A. All rights reserved. Any unauthorized reproduction, photocopy, or use of the information herein, in whole or in part, without the prior written approval of Keithley Instruments, LLC, is strictly prohibited. These are the original instructions in English.
Page 3 Safety precautions The following safety precautions should be observed before using this product and any associated instrumentation. Although some instruments and accessories would normally be used with nonhazardous voltages, there are situations where hazardous conditions may be present. This product is intended for use by personnel who recognize shock hazards and are familiar with the safety precautions required to avoid possible injury.
Page 4 For safety, instruments and accessories must be used in accordance with the operating instructions. If the instruments or accessories are used in a manner not specified in the operating instructions, the protection provided by the equipment may be impaired. Do not exceed the maximum signal levels of the instruments and accessories. Maximum signal levels are defined in the specifications and operating information and shown on the instrument panels, test fixture panels, and switching cards.
Page 5: Table Of Contents
Table of Contents Getting Started General information ..............Warranty information ............Contact information ............Speciﬁcations ..............Safety symbols and terms ........... Inspection ................Options and accessories ............Signal cables and adapters ........... Interface cables ............Rack mount kits ............Product overview ................ Mainframe front and rear panel familiarization ......
Page 6 Connections Connection precautions .............. Testhead preparation ..............Testhead mounting .............. Testhead connections ............Signal connectors ................ Signal connectors ..............Triax DETECTOR connectors ..........CURRENT OUTPUT and VOLTAGE SENSE connectors ..............Interlock connections ..............Remote interlock connections ..........Key interlock ............... Laser diode test connections ............
Page 7 Laser Diode Testing Source and measure conﬁguration menus ........Front panel laser diode testing ........... Test circuit conﬁguration ............ Front panel test procedure ........... Step 1: Conﬁgure laser diode measurement function ..............Step 2: Conﬁgure photodiode detector measurement functions ..............Step 3: Conﬁgure laser diode current source ....
Page 8 Range, Filter, and Math Range ..................Measurement ranges ............Laser diode voltage ranges ........... Photodiode detector current ranges ......Maximum readings ............Setting the measurement range ........Source ranging ..............Remote range programming ..........Range programming example ........Filter ................... Averaging ﬁlter overview ............
Page 9 Triggering Trigger model (front panel operation) ........Idle layer ................Input triggers ............... Delay and pulse phases ............Delay phase ..............Pulse phase ..............Filtering ................ Sweep points ..............Counter ................Output trigger ..............Bench defaults ..............Operation summary ............. Trigger link .................
Page 10 Controlling digital output lines ........... Front panel digital output control ......... Remote digital output control ........Interlocks ..................Interlock operation .............. Interlock status indicator test sequence ....... Reading interlock state ............Pulse sync output ................ Pulse sync waveform ............Pulse sync connections ............Remote Operations Differences: remote vs.
Page 11 Program messages ............10-13 Single command messages ........10-13 Multiple command messages ........10-14 Command path rules ..........10-14 Using common and SCPI commands in the same message .............. 10-15 Program message terminator (PMT) ....... 10-15 Command execution rules ........10-15 Response messages ............
Page 12 Condition registers ............11-17 Event registers ..............11-17 Event enable registers ............11-18 Programming example - program and read register set ............11-19 Queues ..................11-19 Output queue ..............11-19 Error queue ..............11-20 Programming example - read error queue ....11-21 Common Commands Command summary ..............
Page 13 Enable and read math function result ......14-16 STATe ............... 14-16 DATA? ..............14-17 LATest? ..............14-17 DISPlay subsystem ..............14-17 Control display ..............14-17 ENABle ............14-17 ATTRibutes? ............14-18 Read display ..............14-18 DATA? ..............14-18 Deﬁne :TEXT messages ..........
Page 14 Abort sweep ..............14-31 :CABort[:LEVel] <n> ..........14-31 :CABort:STATe ..........14-31 SOURce subsystem ..............14-32 SOURce[1] ..............14-32 Control source outputs on-off .......... 14-32 [:IMMediate] ............14-32 Select sourcing mode ............14-32 MODE <name> ............14-32 Select source function ............. 14-33 FUNCtion[:SHAPe] <name>...
Page 15 Sweep and list program examples ........14-44 Linear staircase sweep ..........14-44 List sweep ..............14-44 Logarithmic staircase sweep ........14-45 SOURce2 and SOURce3 ..........14-46 Set amplitudes ..............14-47 [:IMMediate][:AMPLitude] <n> ......14-47 SOURce4 ................ 14-47 Setting digital output ............14-47 [:LEVel] <NRf>...
Page 16 Reset timestamp .............. 14-55 RESet ............... 14-55 TRACe subsystem ..............14-56 Read sample buffer ............14-56 DATA? ..............14-56 VALue? [<NRf>] ............. 14-56 Conﬁgure sample buffer ..........14-57 POINts <n> .............. 14-57 Trigger subsystem ..............14-57 Initiate source/measure cycle .......... 14-57 INITiate ..............
Page 17 IEEE-488 Bus Overview Introduction ................Bus description ................Bus lines ..................Data lines ................Bus management lines ............Handshake lines ..............Bus commands ................Uniline commands ............. Universal multiline commands .......... Addressed multiline commands ......... Address commands ............Unaddress commands ............Common commands ............
Page 18 Ground loops ..............F-20 Light ................. F-21 Electrostatic interference ..........F-22 Magnetic ﬁelds ..............F-22 Electromagnetic Interference (EMI) ........ F-23 GPIB 488.1 Protocol Introduction ................Selecting the 488.1 protocol ............Protocol differences ..............Message exchange protocol (MEP) ........Using SCPI-based programs ..........Bus hold-off ................
Page 19: Getting Started
Getting Started • General information — Covers general information that includes warranty infor- mation, contact information, safety symbols and terms, inspection, and available options and accessories. • Product overview — Summarizes the features of the Model 2520 Pulsed Laser Diode Test System. •...
Page 20: General Information
Getting Started Model 2520 User’s Manual General information Extended warranty Additional years of warranty coverage are available on many products. These valuable contracts protect you from unbudgeted service expenses and provide additional years of protection at a fraction of the price of a repair. Extended warranties are available on new and existing products.
Page 21: Inspection
Model 2520 User’s Manual Getting Started Inspection The Model 2520 was carefully inspected electrically and mechanically before shipment. After unpacking all items from the shipping carton, check for any obvious signs of physi- cal damage that may have occurred during transit. (There may be a protective ﬁlm over the display lens, which can be removed.) Report any damage to the shipping agent immedi- ately.
Page 22: Interface Cables
Getting Started Model 2520 User’s Manual Interface cables Models 7007-1 and 7007-2 shielded GPIB cables — Connect the Model 2520 to the GPIB bus using shielded cables and connectors to reduce Electromagnetic Interference (EMI). The Model 7007-1 is 1m long; the Model 7007-2 is 2m long. Model 7009-5 shielded RS-232 cable —...
Page 23: Product Overview
Model 2520 User’s Manual Getting Started Product overview The Model 2520 Pulsed Laser Diode Test System combines high-current laser diode pulse and voltage measurement capabilities, and two stable DC bias voltage sources with two low-noise ammeters for dual-channel photodiode measurements. The unit has 0.3% basic laser diode voltage measurement accuracy, and 0.3% basic photodiode current measure- ment accuracy.
Page 24: Mainframe Front And Rear Panel Familiarization
Getting Started Model 2520 User’s Manual Mainframe front and rear panel familiarization Front panel summary The front panel of the Model 2520 mainframe is shown in Figure 1-1. Figure 1-1 Mainframe front panel 2520 PULSED LASER DIODE TEST SYSTEM LASER DETECTOR 1 DETECTOR 2 EDIT...
Page 25: Rear Panel Summary
Model 2520 User’s Manual Getting Started Operation keys: EDIT Enter EDIT mode. MATH Enable math function. LOCAL Cancel remote operation. RECALL Display stored readings and timestamp. FILTER Control digital ﬁlter. DIG OUT Set Digital I/O port output value. TRIG Trigger a measurement from the front panel. SWEEP Start conﬁgured sweep.
Page 26 Getting Started Model 2520 User’s Manual Figure 1-2 Mainframe rear panel WARNING: NO INTERNAL OPERATOR SERVICABLE PARTS, SERVICE BY QUALIFIED PERSONNEL ONLY. IEEE-488 CAT I MADE IN (CHANGE IEEE ADDRESS U.S.A. WITH FRONT PANEL MENU) PULSE DIGITAL I/O SYNC RS-232 TRIGGER LINK TESTHEAD CONN 1...
Page 27: Testhead Front And Rear Panel Familiarization
Model 2520 User’s Manual Getting Started Testhead front and rear panel familiarization Front panel summary The front panel of the Model 2520 testhead is shown in Figure 1-3. Figure 1-3 Testhead front panel CURRENT OUTPUT CURRENT BIAS INPUT CAT I DETECTOR 1 DETECTOR 2 VOLTAGE...
Page 28: Rear Panel Summary
1-10 Getting Started Model 2520 User’s Manual Rear panel summary The rear panel of the Model 2520 testhead is shown in Figure 1-4. Figure 1-4 Testhead rear panel DISABLED (PULL TO REMOVE) BOTH INTERLOCKS MUST BE ENABLED TO OPERATE REMOTE INTERLOCK INTERLOCK ENABLED...
Page 29: Power-Up
Model 2520 User’s Manual Getting Started 1-11 Power-up Line voltage The Model 2520 operates from a line voltage in the range of 100V to 240V at a frequency of 50 or 60Hz. Line voltage selection is automatic. CAUTION Operating the instrument on an incorrect line voltage may cause dam- age, possibly voiding the warranty.
Page 30: System Identification
1-12 Getting Started Model 2520 User’s Manual The communication interface status is brieﬂy displayed. If the IEEE-488 bus is the pres- ently selected interface, the identiﬁcation message will include the primary address. For example, if the primary address is 25 (factory default), the “IEEE Addr=25” message is displayed.
Page 31: Display
Model 2520 User’s Manual Getting Started 1-13 Display Display format The Model 2520 display is used primarily to display measured readings and source values. The top line displays source values and the bottom line shows measured values. Display example The following example shows the unit displaying the laser diode source value on the top line, and the laser diode voltage, detector 1 current and detector 2 current from left to right on the bottom line: Ipulse:100.00mA...
Page 32: Remote Display Programming
1-14 Getting Started Model 2520 User’s Manual Remote display programming The display can also be controlled by various SCPI :DISPlay subsystem commands. Table 1-2 summarizes the basic command to enable or disable the display. See DISPlay subsystem Section 14 for more information on using this and other display commands. Table 1-2 Basic display command Command...
Page 33: Restoring Setups
Model 2520 User’s Manual Getting Started 1-15 Restoring setups Press the SETUP key. From the SAVESETUP MENU, select RESTORE, then press ENTER. Select the setup position (0-4) to restore, then press ENTER to complete the pro- cess. Power-on conﬁguration You can also deﬁne which of the stored setups (factory default or user) the instrument assumes as the power-on conﬁguration as follows: Press the SETUP key.
Page 34 1-16 Getting Started Model 2520 User’s Manual Table 1-3 Factory default settings Setting BENCH default GPIB default Digital output Level Filter: State Disabled Disabled Average count GPIB address No effect No effect Math function format Resistance Resistance M factor (gain) B factor (slope) units units...
Page 35: Remote Setups
Model 2520 User’s Manual Getting Started 1-17 Table 1-3 (continued) Factory default settings Setting BENCH default GPIB default Sweeps (I only) Type None None Direction Sweep points 1000 1000 Start Stop Step Center Span Triggering Trigger input Event Immediate Immediate Timer Input line Trigger output...
Page 36: Main Menu
1-18 Getting Started Model 2520 User’s Manual Main menu Use the MENU key to access the Main Menu to select, conﬁgure, and/or perform various instrument operations. These include default setup conditions, communications (GPIB or RS-232), calibration, front panel tests, digital output states, auto zero, timestamp, and numeric display format.
Page 37: Main Operation Menus
Model 2520 User’s Manual Getting Started 1-19 • A measurement or source range is changed by selecting the function by pressing any one of the LASER or DETECTOR function keys and using the RANGE keys. (The unit must be in the edit mode to change the laser diode source range.) Note that when the next higher or lower range is selected, the reading increases or decreases by a decade.
Page 38 1-20 Getting Started Model 2520 User’s Manual Table 1-5 COMM, SETUP, and DIG OUT menus Menu item Description COMM Select and set up GPIB or RS-232 interface. COMMUNICATIONS SETUP Communications setup menu. GPIB Select and set up GPIB interface. ADDRESS Set primary address (0-30).
Page 39: Configuration Menus
Model 2520 User’s Manual Getting Started 1-21 Table 1-6 PW, DELAY, and COMPL menus Menu item Description Set laser diode current source (I ) pulse width. PW: 0010.uS Pulse width from 500ns to 5ms.* DELAY Set laser diode current source pulse delay. PD: 00.10ms Pulse delay from 20µs to 500ms.* COMPL...
Page 40 1-22 Getting Started Model 2520 User’s Manual Table 1-7 LASER and DETECTOR conﬁguration menus Conﬁguration menu item Description CONFIG LASER V Conﬁgure laser diode voltage measurement. CHANNEL1 POLARITY Select laser diode measurement polarity. POSITIVE Select positive measurement polarity. NEGATIVE Select negative polarity. CONFIG DETECTOR 1 I Conﬁgure photodiode detector #1 current measure ment.
Page 41 Model 2520 User’s Manual Getting Started 1-23 Table 1-8 TRIG and FILTER conﬁguration menus Conﬁguration menu item Description CONFIG TRIG Conﬁgure triggering. CONFIGURE TRIGGER COUNT Specify trigger count. FINITE Programmable count. INFINITE Never ending count. INIT Enable/disable INIT continuous. Turn on continuous. Turn off continuous.
Page 42 1-24 Getting Started Model 2520 User’s Manual Table 1-9 SWEEP and MATH conﬁguration menus Conﬁguration menu item Description CONFIG SWEEP Conﬁgure sweeps for laser diode current source (I CONFIGURE SWEEPS TYPE Select sweep type. NONE Disable sweeps. STAIR Linear staircase sweep, program START, STOP and STEP. Log staircase sweep, program START, STOP, NO OF POINTS.
Page 43: Connections
Connections • Connection precautions — Summarizes precautions that should be observed when making test connections to the Model 2520. • Testhead preparation — Discusses testhead mounting and how to connect the Model 2520 mainframe to the testhead. • Signal connectors — Shows the locations of the signal jacks used for laser diode and photodiode source and measurement and details the terminal conﬁguration of the triax connectors on the testhead.
Page 44: Connection Precautions
Connections Model 2520 User’s Manual Connection precautions WARNING While the Model 2520 does not incorporate a laser, it is designed to operate (power) laser diode devices. Read all safety precautions listed at the beginning of this manual. The following safety practices must be used to protect operators and other users of this product from potential exposure to laser radiation: •...
Page 45: Testhead Preparation
Model 2520 User’s Manual Connections Testhead preparation Testhead mounting The Model 2520 has a mounting ear with two holes (2.5 inches on-center) that allow the unit to be mounted in a location convenient to the test ﬁxture. When mounting the testhead, be sure to allow sufﬁcient clearance around the heat sink for proper cooling.
Page 46 Connections Model 2520 User’s Manual Figure 2-1 Testhead connections Model 2520 Mainframe WARNING: NO INTERNAL OPERATOR SERVICABLE PARTS, SERVICE BY QUALIFIED PERSONNEL ONLY. IEEE-488 CAT I MADE IN (CHANGE IEEE ADDRESS U.S.A. WITH FRONT PANEL MENU) PULSE DIGITAL I/O SYNC RS-232 TRIGGER LINK TESTHEAD...
Page 47: Signal Connectors
Model 2520 User’s Manual Connections Signal connectors Signal connectors Figure 2-2 shows the location of the signal connectors on the front panel of the testhead. These connectors are further described below. Figure 2-2 Testhead signal connectors Model 2520 Testhead CURRENT OUTPUT CURRENT BIAS...
Page 48: Triax Detector Connectors
Connections Model 2520 User’s Manual Triax DETECTOR connectors The electrical conﬁguration of each triax DETECTOR connector is shown in Figure 2-3. Connector terminals are designated as follows: • Center conductor of the connector (and triax cable): current input. This terminal connects to one terminal of the photodiode being used as a detector.
Page 49: Key Interlock
Model 2520 User’s Manual Connections Figure 2-4 Remote interlock connections REMOTE INTERLOCK DISABLED ENABLED Pin 9 Pin 1 Key interlock The key must be inserted into KEY INTERLOCK and rotated to the ENABLED position to operate the unit. Rotate the key to the DISABLED position and remove the key to inhibit the source outputs.
Page 50: Equivalent Circuit
Connections Model 2520 User’s Manual Figure 2-5 Laser diode test connections Center Current Back Conductor Output Photodiode Model 2520 Testhead Triax Cable Detector Optional Earth Inner Shield Ground Connection Shields CURRENT OUTPUT Connected CURRENT BIAS INPUT Laser Diode CAT I DETECTOR 1 DETECTOR 2 Center...
Page 51 Model 2520 User’s Manual Connections Figure 2-6 Equivalent circuit of laser diode test connections Reverse CURRENT Optional Relay OUTPUT Earth Ground Laser Shorting Diode Relay 12-Bit V-Clamp 12-Bit Coaxial Low DAC Cables 16-Bit Current I-DAC Source -25V VOLTAGE SENSE 14-Bit V-Measure 1MΩ...
Page 52: Connection Considerations
2-10 Connections Model 2520 User’s Manual Connection considerations When making connections to the laser diode, observe the following considerations to avoid pulse degradation due to distributed inductance and other effects: • Use only the supplied 15Ω coaxial cables. • Keep cable lengths to a minimum. •...
Page 53: Basic Operation
Basic Operation • Operation overview — Discusses current and voltage source and measure capabil- ities, ranges, compliance, and fundamental measurement and voltage bias circuit conﬁguration. • Conﬁguring sources — Covers setting up the laser diode current source and photodiode voltage bias source values. •...
Page 54: Operation Overview
Basic Operation Model 2520 User’s Manual Operation overview Laser diode source and measure capabilities The Model 2520 has the following laser diode current source and voltage measurement capabilities: • Source Current — The Model 2520 can source DC current to the laser diode from 8µA to 1A (DC or pulse mode), 5.0A (pulse mode only).
Page 55: Laser Diode Source Compliance
Model 2520 User’s Manual Basic Operation Table 3-2 Laser diode voltage measurement ranges Voltage Maximum range Resolution reading 0.33mV ±5.25V 0.66mV ±10.5V Laser diode source compliance The laser diode current source has a maximum DC output level of 1A @ 9.9V, for a maxi- mum power of 9.9W.
Page 56: Photodiode Source And Measure Ranges
Basic Operation Model 2520 User’s Manual Photodiode source and measure ranges Table 3-3 summarizes photodiode current measurement ranges, resolutions, and maxi- mum readings. Note that each photodiode voltage bias source has a single 20V range. See Section 6 for more details on ranging. Table 3-3 Photodiode current measurement ranges Current...
Page 57: Basic Circuit Configuration
Model 2520 User’s Manual Basic Operation Basic circuit conﬁguration The fundamental circuit conﬁguration for Model 2520 is shown in Figure 3-1. (See Figure 2-6 for a more detailed equivalent circuit.) In addition to the laser diode current source and voltage measurement circuits, the unit has two separate photodiode channels, each of which includes a feedback ammeter and a 0-±20V voltage bias source.
Page 58: Polarity
Basic Operation Model 2520 User’s Manual Polarity Polarity for the laser diode current source, both detector current measurements, and laser diode voltage measurement can be controlled by using the POLARITY selections in the corresponding conﬁguration menus (see “Conﬁguring sources,” page 3-9, and “Conﬁgur- ing measurements,”...
Page 59: Laser Diode Voltage Measurement Polarity
Model 2520 User’s Manual Basic Operation Laser diode voltage measurement polarity Figure 3-3 shows the basic conﬁguration for laser diode voltage measurement polarity. Figure 3-3A shows correct connections for POSITIVE polarity. In this case, the laser diode positive terminal is connected to the VOLTAGE SENSE HI terminal, while the neg- ative laser diode terminal is connected to the VOLTAGE SENSE LO terminal.
Page 60: Detector Measurement Polarity
Basic Operation Model 2520 User’s Manual Detector measurement polarity Figure 3-4 shows the basic conﬁguration for detector current measurement polarity. With connections shown in Figure 3-4A, current will ﬂow into the current input (center conduc- tor of the triax connector). Under these conditions, the measured current is negative, and the polarity setting must also be NEGATIVE.
Page 61: Configuring Sources
Model 2520 User’s Manual Basic Operation Conﬁguring sources Follow the general procedures below to set source and compliance values for the laser diode current source as well as bias voltage values for the two photodiode sources. Editing source values Use the following keys to edit source values: •...
Page 62: Configuring Laser Diode Source
3-10 Basic Operation Model 2520 User’s Manual Conﬁguring laser diode source The basic procedure for setting up laser diode current source values for both DC and pulse modes is outlined below. DC mode Press CONFIG then LASER I to access the source conﬁguration menu. Choose POLARITY, then press ENTER.
Page 63: Pulse Mode
Model 2520 User’s Manual Basic Operation 3-11 Pulse mode Press CONFIG then LASER I to access the source conﬁguration menu. Choose POLARITY, then press ENTER. Select POSITIVE or NEGATIVE as desired, then press ENTER (Figure 3-2). Select SHAPE, then press ENTER. Choose PULSE, then press ENTER.
Page 64: Configuring Measurements
3-12 Basic Operation Model 2520 User’s Manual Conﬁguring measurements Follow the general procedures below to set the range and polarity for both laser diode and photodiode measurements. NOTE The pulse width setting affects not only the source, but the measurement as well. The larger the pulse width, the more A/D samples that will be averaged to gener- ate a measurement, which decreases noise, but increases test time.
Page 65: Remote Source And Measure Configuration
Model 2520 User’s Manual Basic Operation 3-13 Remote source and measure conﬁguration Source and measure conﬁguration can also be performed via remote by sending appropri- ate commands. The following paragraphs summarize these commands and give a simple programming example. Source and measure conﬁguration commands Table 3-4 summarizes commands used for source and measure conﬁguration.
Page 66 3-14 Basic Operation Model 2520 User’s Manual Programming example Table 3-5 summarizes the command sequence for basic source and measure conﬁguration. NOTE Section 4 for complete test procedures. These commands set up the Model 2520 as follows: • Laser diode voltage measurement range and polarity: 10V, positive. •...
Page 67: Laser Diode Testing
Laser Diode Testing • Source and measure conﬁguration menus — Brieﬂy summarizes the menus for conﬁguring the laser diode source as well as all three measurement functions. • Front panel laser diode testing — Provides a detailed procedure for performing laser diode tests from the front panel.
Page 68: Source And Measure Configuration Menus
Laser Diode Testing Model 2520 User’s Manual Source and measure conﬁguration menus Table 4-1 summarizes the measurement and source conﬁguration menus used in this sec- tion. See Section 3 for conﬁguration procedures. WARNING It is the responsibility of the customer to operate instruments in a safe manner.
Page 69: Front Panel Laser Diode Testing
Model 2520 User’s Manual Laser Diode Testing Front panel laser diode testing Test circuit conﬁguration The basic circuit conﬁguration for the laser diode test procedures in this section is shown Figure 4-1. (See Figure 2-5 for a more detailed drawing.) Note that connections for laser diode as well as both photodiode detectors are included, but the required interlock connections are not shown.
Page 70: Front Panel Test Procedure
Laser Diode Testing Model 2520 User’s Manual Front panel test procedure Step 1: Conﬁgure laser diode measurement function. Conﬁgure the laser diode measurement function as follows: Press CONFIG then LASER V Choose POSITIVE or NEGATIVE polarity as desired, then press ENTER. Press LASER V , then use the RANGE keys to choose the measurement...
Page 71: Step 5: Configure Math Functions
Model 2520 User’s Manual Laser Diode Testing Press DETECTOR 2 V to select the photodiode #2 source. Again, using either the EDIT or numeric entry keys, set the bias source value to the desired value. Step 5: Conﬁgure math functions. Set up your math functions as desired.
Page 72 Laser Diode Testing Model 2520 User’s Manual Table 4-2 Laser diode test commands Command Description :CALCulate[1]:FORMat <format> Deﬁne laser diode math format (MXB[1], CONDuctance[1]), POWER[1], or RESistance[1]). :CALCulate[1]:DATA? Request laser diode math reading. :CALCulate[1]:STATe <state> Enable/disable laser diode math (ON or OFF). :CALCulate[1]:KMATh:MBFactor ...
Page 73: Programming Example
Model 2520 User’s Manual Laser Diode Testing Table 4-2 (continued) Laser diode test commands Command Description :SOURce[1]:CURRent:MODE FIXed Select ﬁxed (not sweep) laser diode current source mode. :SOURce[1]:CURRent:RANGe <range> Select laser diode source range (0.5 or 5). :SOURce[1]:CURRent <current> Set laser diode source current (0 to +5.0). :SOURce[1]:CURRent:POLarity <polarity>...
Page 74 Laser Diode Testing Model 2520 User’s Manual NOTE Appendix H for a functional program example. Table 4-3 Basic laser diode test command sequence Step Action Commands Comments *RST Restore GPIB defaults. Conﬁgure laser diode measure. :SENS1:VOLT:RANG 10 LD measure range = 10V. :SENS1:VOLT:POL POS LD positive polarity.
Page 75: Source-Measure Concepts
Source-Measure Concepts • Pulse concepts — Describes the various aspects of the laser diode current source pulse mode. • Sweep operation — Covers the various types of sweeps that can be performed. • Operating boundaries — Covers output and limit operating boundaries for the laser diode current source.
Page 76: Pulse Concepts
Source-Measure Concepts Model 2520 User’s Manual Pulse concepts Overview The Model 2520 laser diode current source can output either DC or pulse waveforms. Maximum current is as follows: • DC: 1A • Pulse mode: 5A In addition, the current source can be operated in either the ﬁxed or sweep mode. In the ﬁxed mode, the source simply outputs the programmed DC level (DC mode), or pulses at a ﬁxed amplitude (pulse mode).
Page 77: Delay Phase
Model 2520 User’s Manual Source-Measure Concepts Delay phase The programmable delay speciﬁes the minimum time between two pulses (pulse off time) in a sweep. Note that data processing is part of the delay phase (Figure 5-1). The time needed for data processing is directly related to the length of the pulse phase. As the pulse width becomes large relative to the pulse delay, the actual time between pulses will depend more on the processing time rather than the programmable delay period.
Page 78: Front Panel Pulse Parameters
Source-Measure Concepts Model 2520 User’s Manual Front panel pulse parameters Fixed mode Figure 5-2 shows how various front panel programming parameters control various ﬁxed pulse waveform aspects. These parameters are programmed by pressing the appropriate key: • LASER I — sets the pulse amplitude. •...
Page 79 Model 2520 User’s Manual Source-Measure Concepts Figure 5-3 Front panel staircase sweep mode pulse parameters Stop Step Start Delay Returns to 0A because pulse is less than Low. Figure 5-4 shows how various front panel programming parameters control various stair- case sweep DC waveform aspects.
Page 80: Remote Pulse Parameters
Source-Measure Concepts Model 2520 User’s Manual Remote pulse parameters Fixed mode Figure 5-5 shows how various remote commands control various ﬁxed pulse waveform aspects. These parameters are programmed as follows: • SOUR1:CURR — sets the pulse amplitude. • SOUR1:PULS :DEL — sets the pulse delay (time between pulses). •...
Page 81: Pulse Rise And Fall Times
Model 2520 User’s Manual Source-Measure Concepts Figure 5-6 Remote staircase sweep mode pulse parameters SOUR1:CURR:STOP SOUR1:CURR:STEP SOUR1:CURR:LOW Start SOUR1:CURR:START SOUR1:PULS:DEL SOUR1:PULS:WIDT Returns to 0A because pulse is less than Low. Pulse rise and fall times As shown in Figure 5-7, there are two additional pulse characteristics that require discus- sion: rise time and fall time.
Page 82: Sweep Waveforms
Source-Measure Concepts Model 2520 User’s Manual Sweep waveforms There are three basic sweep types available: linear staircase, logarithmic staircase, and custom. NOTE Staircase sweeps can be programmed both from the front panel and via remote, while custom sweeps are available only via remote. Staircase sweeps As shown in Figure...
Page 83 Model 2520 User’s Manual Source-Measure Concepts Figure 5-8 Sweep waveform types Stop Start Linear Staircase Sweep Stop Start Logarithmic scale shown for staircase steps. Logarithmic Staircase Sweep First Point Last Point Custom Sweep Note: DC mode waveforms shown. Figure 5-9 Custom sweep waveform SOUR1:LIST:CURR SOUR1:CURR:LOW...
Page 84: Current Source Operating Boundaries
5-10 Source-Measure Concepts Model 2520 User’s Manual Current source operating boundaries Limit lines Figure 5-10 shows the operating boundaries, or limit lines for the laser diode current source. In the DC mode, the current source can output a maximum of 1A @ 9.9V. In the pulse mode, the current source can output 5A @ 9.5V.
Page 85 Model 2520 User’s Manual Source-Measure Concepts 5-11 Figure 5-11 Loading effects Voltage Limit Load Line 10.5V Output Voltage (V) Operating Point Current Source Load Line 100mA Output Current (mA) V = I • R = (100mA)(50Ω) = 5V A. Normal Current Source Operation Voltage Limit Load Line Operating...
Page 86: Data Flow
5-12 Source-Measure Concepts Model 2520 User’s Manual Notice that as resistance increases, the slope of the DUT load line increases. As resistance approaches inﬁnity (open output), the Model 2520 will source virtually 0mA at 10.5V. Conversely, as resistance decreases, the slope of the DUT load line decreases. At zero resistance (shorted output), the Model 2520 will source virtually 100mA at 0V.
Page 87 Model 2520 User’s Manual Source-Measure Concepts 5-13 Figure 5-12 Data ﬂow-front panel Laser Voltage and Display Normal Detector Current Voltage and Current Functions Readings A. Math Function and Sweeps Disabled Display Math Math Function Readings Function B. Math Function Enabled Laser Voltage and Display Buffer, Sweep...
Page 88: Range, Filter, And Math
Range, Filter, and Math • Range — Discusses available ranges, maximum readings and source values, and ranging limitations. • Filter — Provides information on the ﬁltering process that can be used to reduce reading noise. • Math — Outlines the math functions that can be performed on laser diode voltage measurement and photodiode current measurement data.
Page 89: Range
Range, Filter, and Math Model 2520 User’s Manual Range Measurement ranges The selected measurement range affects the accuracy of the laser diode voltage measure- ments, photodiode detector current measurements, as well as the maximum signal that can be measured. Laser diode voltage ranges Table 6-1 summarizes laser diode voltage ranges, resolution, and maximum readings.
Page 90: Maximum Readings
Model 2520 User’s Manual Range, Filter, and Math Maximum readings The full scale input for each measurement range is shown in Table 6-1 Table 6-2. Input levels that exceed the maximum levels cause the “Oﬂow” message to be displayed. Setting the measurement range Press the LASER V , DETECTOR 1 I or DETECTOR 2 I...
Page 91: Range Programming Example
Range, Filter, and Math Model 2520 User’s Manual Range programming example Table 6-5 shows a programming example for controlling range. The Model 2520 is set up as follows: • Laser diode voltage measure range: 5V. • Laser diode current source range: 500mA. •...
Page 92: Filter Configuration
Model 2520 User’s Manual Range, Filter, and Math Figure 6-1 Averaging ﬁlter during sweep 30mA Step Start = 10mA Stop = 30mA Step = 10mA 20mA Step 10mA Step With filter count = 3, three delay-pulse cycles are performed at each sweep step. Filter conﬁguration NOTE The average ﬁlter setting is global and affects all three measurements (laser...
Page 93: Filter Programming Example
Range, Filter, and Math Model 2520 User’s Manual NOTE Filter commands are global. Changing the setting using the commands for one measurement function affects ﬁltering for the other two functions. Table 6-6 Filter commands Commands Description [:SENSe[1]]:AVERage:COUNt <count> Set average ﬁlter count (1 to 100). [:SENSe[1]]:AVERage[:STATe] <state>...
Page 94: Conductance
Model 2520 User’s Manual Range, Filter, and Math Conductance This math function computes the conductance from the ratio between the laser diode cur- rent source value and the measured voltage: Conductance = I where: = laser diode source current = measured laser diode voltage Resistance This math function computes the resistance using the ratio between the measured laser diode voltage and the source current:...
Page 95: Front Panel Math Functions
Range, Filter, and Math Model 2520 User’s Manual Front panel math functions Math conﬁguration menu Table 6-8 summarizes the math conﬁguration menu. Press CONFIG then MATH to access the menu. Table 6-8 Math conﬁguration menu Conﬁguration menu item Description CONFIGURE MATH CHANNEL1 Program V (laser diode voltage) math function.
Page 96: Remote Math Functions
Model 2520 User’s Manual Range, Filter, and Math Remote math functions Math function commands Table 6-9 summarizes commands to control the measurement math functions by remote. “Calculate subsystems,” page 14-14, for detailed information. Table 6-9 Math function commands Command Description :CALCulate[1]:DATA? Request laser diode math reading.
Page 97: Math Function Programming Example
6-10 Range, Filter, and Math Model 2520 User’s Manual Math function programming example Table 6-10 summarizes commands that program the following math function parameters: • Laser diode math function: power • Detector #1 MX + B slope (M): 0.5 • Detector #1 MX + B offset (B): 5e-3 Table 6-10 Math function programming example...
Page 98: Sweep Operation
Sweep Operation • Sweep types — Describes the three basic sweep types: Linear staircase, logarith- mic staircase, and custom sweep. • Conﬁguring and running a sweep — Discusses the procedure for setting up and performing sweeps including selecting and conﬁguring a sweep and performing a sweep.
Page 99: Sweep Types
Sweep Operation Model 2520 User’s Manual Sweep types The three basic sweep types described in the following paragraphs include: • Linear staircase • Logarithmic staircase • Custom NOTE Linear and logarithmic staircase sweeps are available both from the front panel and via remote.
Page 100: Logarithmic Staircase Sweep
Model 2520 User’s Manual Sweep Operation Logarithmic staircase sweep This sweep is similar to the linear staircase sweep. The steps, however, are done on a loga- rithmic scale as shown in the example sweep in Figure 7-2. This is a 5-point log sweep from 1mA to 10mA.
Page 101 Sweep Operation Model 2520 User’s Manual Thus, the ﬁve log steps for this sweep are 0, 0.25, 0.50, 0.75, and 1.00mA. The actual cur- rent source levels at these points are listed in Table 7-1 (the current level is the anti-log of the log step).
Page 102: Configuring And Running A Sweep
Model 2520 User’s Manual Sweep Operation Conﬁguring and running a sweep Front panel sweep operation Conﬁguring a sweep The sweep conﬁguration menu is structured as follows and shown in Figure 7-4. Note that bullets indicate the primary items of the sweep menu and dashes indicate the options of each menu item.
Page 103: Performing Sweeps
Sweep Operation Model 2520 User’s Manual Performing sweeps Procedures for the various sweep types are covered below. NOTE The following procedure assumes that the Model 2520 is already connected to the DUT as explained in Section Performing a linear staircase sweep Step 1: Conﬁgure source and measure.
Page 104: Performing A Log Staircase Sweep
Model 2520 User’s Manual Sweep Operation Performing a log staircase sweep Step 1: Conﬁgure source and measure. Conﬁgure the Model 2520 source and measure functions as follows: Select the current source range by pressing LASER I then EDIT, then use the RANGE keys.
Page 105: Remote Sweep Operation
Sweep Operation Model 2520 User’s Manual Remote sweep operation Staircase sweep commands Table 7-2 summarizes remote commands used for linear and log staircase sweep opera- tion. See Section “Conﬁgure sweeps,” for more details on these commands. Table 7-2 Linear and log staircase sweep commands Command Description* :SOURce[1]:CURRent:MODE SWEep...
Page 106: Staircase Sweep Programming Example
Model 2520 User’s Manual Sweep Operation Staircase sweep programming example As an example of linear staircase sweep operation, assume the Model 2520 is to be used to test a laser diode. For the purposes of this test, assume the following basic sweep parameters: •...
Page 107: Custom Sweep Commands
7-10 Sweep Operation Model 2520 User’s Manual Custom sweep commands Table 7-4 summarizes remote commands used for custom sweep operation. See Section “Conﬁgure list,” for more details on these commands. Table 7-4 Custom sweep commands Command Description :SOURce[1]:CURRent:MODE LIST Select current list (custom) sweep mode. :SOURce[1]:LIST:CURRent <...
Page 108 Model 2520 User’s Manual Sweep Operation 7-11 Table 7-5 summarizes the basic remote command sequence for performing the custom sweep described above. Table 7-5 Custom sweep programming example Command Description *RST Restore GPIB default conditions. :FORM:ELEM VOLT1,CURR2,CURR3 Laser diode voltage, detector current data. :SOUR1:CURR:MODE LIST Current list sweep mode.
Page 109: Triggering
Triggering • Trigger model — Discusses the trigger model, including various layers, input trig- gers, and output trigger. • Trigger link — Discusses the trigger link, including input triggers and output trig- gers. • Conﬁguring triggering — Details how to conﬁgure the various triggering aspects from the front panel.
Page 110: Trigger Model (Front Panel Operation)
Triggering Model 2520 User’s Manual Trigger model (front panel operation) The ﬂowchart in Figure 8-1 summarizes triggering for front panel operation. The trigger model is modeled after the remote commands used to control triggering. Refer to “Trigger model (remote operation),” page 8-9.
Page 111: Idle Layer
Model 2520 User’s Manual Triggering Idle layer The Model 2520 is in the Idle Layer when it is not operating in the Trigger Layer of the trigger model. The Model 2520 can be returned to idle at any time by selecting the HALT menu item of the CONFIGURE TRIGGER menu.
Page 112: Pulse Phase
Triggering Model 2520 User’s Manual Pulse phase During the pulse phase, the unit outputs one current pulse with the programmed pulse width (set to between 500ns and 5ms with the PW key). If the unit is in the ﬁxed (non- sweep mode), the pulse amplitude is the same for each cycle through the loop.
Page 113: Bench Defaults
Model 2520 User’s Manual Triggering Bench defaults The bench defaults are listed as follows. They are also denoted in Figure 8-1 by the “✛” symbol. • Trigger-In Event = Immediate • Trigger Count = 1 • Timer = 0.1s • Trigger Out Event = Off Unless programmed otherwise, the Model 2520 will run in a continuous loop around the trigger model, processing one set of readings each time it goes through the loop.
Page 114: Input Trigger Requirements
Triggering Model 2520 User’s Manual Input trigger requirements An input trigger is used to satisfy event detection for a trigger model layer that is conﬁg- ured for the TRIGGER LINK event. See “Trigger model (front panel operation),” page 8-2. The input requires a falling-edge, TTL compatible pulse with the speciﬁcations shown in Figure 8-3.
Page 115: Configuring Triggering
Model 2520 User’s Manual Triggering Conﬁguring triggering Triggering is conﬁgured from the CONFIGURE TRIGGER menu and is structured as fol- lows. NOTE “Trigger model (front panel operation),” page 8-2, for details on the follow- ing programmable aspects of triggering. CONFIGURE TRIGGER menu Press CONFIG and then TRIG to display the menu shown below and in Figure 8-5.
Page 116 Triggering Model 2520 User’s Manual ↓STEST — Event detection occurs when the SOT line of the Digital I/O port • is pulsed low (See Section ↑STEST — Event detection occurs when the SOT line of the Digital I/O port • is pulsed high.
Page 117: Remote Triggering
Model 2520 User’s Manual Triggering Remote triggering Trigger model (remote operation) The trigger model ﬂowchart in Figure 8-6 summarizes remote trigger operation. Operation is controlled by SCPI commands from the Trigger Subsystem. Key remote commands are included in the trigger model. Also note that the GPIB defaults are denoted by the “✛” symbol.
Page 118 8-10 Triggering Model 2520 User’s Manual Figure 8-6 Trigger model (remote operation) See Note Note: The following commands place the Model 2520 into idle: DCL, SDC, ABORt, *RST, SYSTem:PREset, and *RCL. INITiate Idle Turn On Outputs Trigger Layer TRIGger:SOURce Another TRIGger:COUNt ✛...
Page 119: Event Detection
Model 2520 User’s Manual Triggering 8-11 While operating within the trigger layer, most commands will not be executed until the Model 2520 completes all of its programmed source-measure operations and returns to the idle state. However, these commands will be processed while not in the idle state: •...
Page 120: Delay And Pulse Phases
8-12 Triggering Model 2520 User’s Manual Delay and pulse phases The delay-pulse cycle consists of two phases: Delay and Pulse. (See Section 5 for details.) Delay phase The programmable delay is the time period between current pulses. The delay is set with the :DELay commands and can be programmed in the range of 20µs to 500ms.
Page 121: Output Trigger
Model 2520 User’s Manual Triggering 8-13 Output trigger As shown in Figure 8-6, the Model 2520 can be programmed to output a trigger when operation leaves the Trigger Layer. This output trigger is typically sent to another instru- ment to signal the end of a sweep. The TRIG:OUTPut command is used to control this output trigger.
Page 122: Remote Trigger Example
8-14 Triggering Model 2520 User’s Manual Table 8-1 Remote trigger commands Command Description :INITiate Take Model 2520 out of idle state. :ABORt Reset trigger system. :TRIGger:COUNt <count> Set trigger count (1 to 5000). :TRIGger:ILINe <line> Select trigger link input line (1 to 6). :TRIGger:OLINe <line>...
Page 123 Digital I/O Port, Interlocks, and Pulse Sync Output • Digital I/O Port — Discusses the various input/output lines on the Digital I/O Port as well as the +5V line that can be used to power external logic circuits. • Interlocks — Describes how to use to determine the status of the interlocks. •...
Page 124: Digital I/O Port, Interlocks, And Pulse Sync Output
Digital I/O Port, Interlocks, and Pulse Sync Output Model 2520 User’s Manual Digital I/O port The Model 2520 has a digital input/output port that can be used to control external digital circuitry. Port conﬁguration The Digital I/O Port is located on the rear panel and is shown in Figure 9-1.
Page 125: Start-Of-Test (Sot) Line
Model 2520 User’s Manual Digital I/O Port, Interlocks, and Pulse Sync Output Start-of-test (SOT) line The input line (SOT) is a TTL-compatible logic line used by external equipment to start a test. With the ↓STEST trigger event selected, a low SOT pulse starts the testing process. With the ↑STEST trigger event selected, a high SOT pulse starts the testing process.
Page 126: Source Operation
Digital I/O Port, Interlocks, and Pulse Sync Output Model 2520 User’s Manual Source operation Figure 9-3 shows the basic output conﬁguration for source operation. In this case, the external relay coil is connected between the digital output line (pins 1 to 4) and ground (pin 9).
Page 127: Remote Digital Output Control
Model 2520 User’s Manual Digital I/O Port, Interlocks, and Pulse Sync Output Remote digital output control Use the :SOURce4:TTL <NRf> command to control the digital output line logic levels, where <NRf> is the decimal value shown in Table 9-1. For example, send the following command to set the output lines to L, H, L, H: :SOUR4:TTL 5 Table 9-1...
Page 128: Interlock Operation
Digital I/O Port, Interlocks, and Pulse Sync Output Model 2520 User’s Manual Interlock operation Figure 9-4 shows typical connections to the REMOTE INTERLOCK connector. If the ﬁx- ture switch is closed (Figure 9-4A), the three source outputs are enabled and can be turned on.
Page 129: Interlock Status Indicator Test Sequence
Model 2520 User’s Manual Digital I/O Port, Interlocks, and Pulse Sync Output Interlock status indicator test sequence Perform the following steps to verify the operation of the indicator lights: Remove any connections from the testhead CURRENT OUTPUT, VOLTAGE SENSE, or DETECTOR terminals. Connect the testhead to the mainframe, and follow the steps for power connection and power-up sequence in Section...
Page 130: Pulse Sync Output
Digital I/O Port, Interlocks, and Pulse Sync Output Model 2520 User’s Manual Pulse sync output The Model 2520 has a pulse sync output that allows synchronization of external equip- ment to the laser diode current source pulse. Pulse sync waveform Figure 9-5 shows the pulse sync waveform, which is a 5V pulse with 50Ω...
Page 131: Pulse Sync Connections
Model 2520 User’s Manual Digital I/O Port, Interlocks, and Pulse Sync Output Pulse sync connections Figure 9-6 shows typical pulse sync connections. Use quality BNC 50Ω RG-58 cable to avoid pulse distortion that could cause timing and jitter problems. Figure 9-6 Pulse sync out connections Pulse Sync Coax Cable...
Page 132: Remote Operations
Remote Operations • Differences: remote vs. local operation — Summarizes remote operation enhancements and local-to-remote and remote-to-local transitions. • Selecting an interface — Describes how to select between the GPIB and RS-232 interfaces. • GPIB operation — Covers GPIB bus standards, bus connections, and primary address selection.
Page 133: Differences: Remote Vs. Local Operation
10-2 Remote Operations Model 2520 User’s Manual Differences: remote vs. local operation Local-to-remote transition When changing from local to remote operation, the following takes place: • The Model 2520 stops taking readings and is placed into the Idle layer of the Trig- ger Model.
Page 134: Gpib Operation
Model 2520 User’s Manual Remote Operations 10-3 The RS-232 interface is a serial interface. Programmable aspects of this interface include the following (factory default settings are shown in parentheses): • Baud rate (9600) • Data bits (8) • Parity (none) •...
Page 135: Gpib Connections
10-4 Remote Operations Model 2520 User’s Manual GPIB connections To connect the Model 2520 to the GPIB bus, use a cable equipped with standard IEEE-488 connectors as shown in Figure 10-1. Figure 10-1 IEEE-488 connector To allow many parallel connections to one instrument, stack the connectors. Two screws are located on each connector to ensure that connections remain secure.
Page 136 Model 2520 User’s Manual Remote Operations 10-5 NOTE To minimize interference caused by electromagnetic radiation, use only shielded IEEE-488 cables. Available shielded cables from Keithley are Models 7007-1 and 7007-2. To connect the Model 2520 to the IEEE-488 bus, follow these steps: Line up the cable connector with the connector located on the rear panel.
Page 137: Primary Address
10-6 Remote Operations Model 2520 User’s Manual Primary address The Model 2520 ships from the factory with a GPIB primary address of 25. When the unit powers up, it momentarily displays the primary address. You can set the address to a value from 0 to 30, but do not assign the same address to another device or to a controller that is on the same GPIB bus (controller addresses are usually 0 or 21).
Page 138: Ren (Remote Enable)
Model 2520 User’s Manual Remote Operations 10-7 REN (remote enable) The remote enable command is sent to the Model 2520 by the controller to set up the instrument for remote operation. Generally, the instrument should be placed in the remote mode before you attempt to program it over the bus.
Page 139: Sdc (Selective Device Clear)
10-8 Remote Operations Model 2520 User’s Manual When the Model 2520 receives a DCL command, it clears the Input Buffer and Output Queue, cancels deferred commands, and clears any command that prevents the processing of any other device command. A DCL does not affect instrument settings and stored data. SDC (selective device clear) The SDC command is an addressed command that performs essentially the same function as the DCL command.
Page 140: Gpib Status Indicators
Model 2520 User’s Manual Remote Operations 10-9 GPIB status indicators The REM (remote), TALK (talk), LSTN (listen), and SRQ (service request) annunciators show the GPIB bus status. Each of these indicators is described below. This indicator shows when the instrument is in the remote state. REM does not necessarily indicate the state of the bus REN line, as the instrument must be addressed to listen with REN true before the REM indicator turns on.
Page 141: Programming Syntax
10-10 Remote Operations Model 2520 User’s Manual Programming syntax The information in this section covers syntax for both common commands and SCPI com- mands. For information not covered here, see the IEEE-488.2 and SCPI standards. See Section 12 Section 14 for more details on common and SCPI commands, respectively.
Page 142 Model 2520 User’s Manual Remote Operations 10-11 Example: <name> = NONE :TRIGger:OUTPut NONE <NRf> Numeric representation format — This parameter is a number that can be expressed as an integer (e.g., 8), a real number (e.g., 23.6), or an exponent (2.3E6).
Page 143: Query Commands
10-12 Remote Operations Model 2520 User’s Manual Query commands This type of command requests (queries) the presently programmed status. It is identiﬁed by the question mark (?) at the end of the fundamental form of the command. Most com- mands have a query form: :SOURce1:PULSe:DELay? Queries the pulse delay.
Page 144: Short-Form Rules
Model 2520 User’s Manual Remote Operations 10-13 Short-form rules Use the following rules to determine the short-form version of any SCPI command: • If the length of the command word is four letters or less, no short form version exists. Example: •...
Page 145: Multiple Command Messages
10-14 Remote Operations Model 2520 User’s Manual :stat:oper:enab <NRf> :stat:oper:enab? :stat:pres In each of the above program messages, the path pointer starts at the root command (:stat) and moves down the command levels until the command is executed. Multiple command messages You can send multiple command messages in the same program message as long as they are separated by semicolons (;).
Page 146: Using Common And Scpi Commands In The Same Message
Model 2520 User’s Manual Remote Operations 10-15 Using common and SCPI commands in the same message Both common commands and SCPI commands can be used in the same message as long as they are separated by semicolons (;). A common command can be executed at any com- mand level and will not affect the path pointer.
Page 147: Response Message Terminator (Rmt)
10-16 Remote Operations Model 2520 User’s Manual Response message terminator (RMT) Each response is terminated with an LF (Line Feed) and EOI (end or identify). The fol- lowing example shows how a multiple response message is terminated: 0; 1; 1; 0 <RMT> Message exchange protocol Two rules summarize the message exchange protocol: Rule 1.
Page 148: Data Bits And Parity
Model 2520 User’s Manual Remote Operations 10-17 • 9600 • 4800 • 2400 • 1200 • • The factory selected baud rate is 9600. When you choose a baud rate, make sure the programming terminal or printer that you are connecting to the Model 2520 can support the baud rate you selected.
Page 149: Rs-232 Connections
10-18 Remote Operations Model 2520 User’s Manual If NONE is the selected ﬂow control, there will be no signal handshaking between the controller and the Model 2520. Data will be lost if transmitted before the receiving device is ready. RS-232 connections The RS-232 serial port (Figure 10-3) is connected to the serial port of a computer using a...
Page 150 Model 2520 User’s Manual Remote Operations 10-19 Table 10-2 RS-232 connector pinout Pin number Description Not used TXD, transmit data RXD, receive data Not used GND, signal ground Not used RTS, ready to send CTS, clear to send Not used Note: CTS and RTS are tied together.
Page 151: Error Messages
10-20 Remote Operations Model 2520 User’s Manual Error messages Appendix B for RS-232 error messages. Programming example The following QuickBasic 4.5 programming example will control the Model 2520 via the RS-232 COM2 port. Place the Model 2520 into the RS-232 mode from the front panel main menu (press COMM then select RS-232).
Page 152: Status Structure
Status Structure • Overview — Provides an operational overview of the status structure for the Model 2520. • Clearing registers and queues — Covers the actions that clear (reset) registers and queues. • Programming and reading registers — Explains how to program enable registers and read any register in the status structure.
Page 153: Overview
11-2 Status Structure Model 2520 User’s Manual Overview The Model 2520 provides a series of status registers and queues allowing the operator to monitor and manipulate the various instrument events. The status structure is shown in Figure 11-1. The heart of the status structure is the Status Byte Register. This register can be read by the user's test program to determine if a service request (SRQ) has occurred, and what event caused it.
Page 154 Model 2520 User’s Manual Status Structure 11-3 Figure 11-1 Model 2520 status register structure Questionable Questionable Questionable Event Condition Event Enable Register Register Register & & & & & & & Logical & Calibration Summary & & Error Queue & &...
Page 155: Clearing Registers And Queues
11-4 Status Structure Model 2520 User’s Manual Clearing registers and queues When the Model 2520 is turned on, the bits of all registers in the status structure are cleared (reset to 0), and the two queues are empty. Commands to reset the event and event enable registers, and the Error Queue are listed in Table 11-1.
Page 156: Programming And Reading Registers
Model 2520 User’s Manual Status Structure 11-5 Programming and reading registers Programming enable registers The only registers that can be programmed by the user are the enable registers. All other registers in the status structure are read-only registers. The following explains how to ascertain the parameter values for the various commands used to program enable registers.
Page 157: Reading Registers
11-6 Status Structure Model 2520 User’s Manual The <NDN> (non-decimal numeric) parameter type is used to send non-decimal values. These values require a header (#B, #H, or #Q) to identify the data format being sent. The letter in the header can be upper or lower case. The <NRf> (numeric representation for- mat) parameter type is used to send decimal values, and does not use a header.
Page 158: Status Byte And Service Request (Srq)
Model 2520 User’s Manual Status Structure 11-7 Table 11-2 Data format commands for reading status registers Command Description Default :FORMat:SREGister <name> Select data format for reading status registers: ASCii <name> = ASCii Decimal format HEXadecimal Hexadecimal format OCTal Octal format BINary Binary format Status byte and service request (SRQ)
Page 159: Status Byte Register
11-8 Status Structure Model 2520 User’s Manual Status byte register The summary messages from the status registers and queues are used to set or clear the appropriate bits (B0, B2, B3, B4, B5, and B7) of the Status Byte Register. These summary bits do not latch, and their states (0 or 1) are solely dependent on the summary messages (0 or 1).
Page 160: Serial Polling And Srq
Model 2520 User’s Manual Status Structure 11-9 is applied to the input of the OR gate and, therefore, sets the MSS/RQS bit in the Status Byte Register. The individual bits of the Service Request Enable Register can be set or cleared by using the *SRE common command.
Page 161: Status Byte And Service Request Commands
11-10 Status Structure Model 2520 User’s Manual Status byte and service request commands The commands to program and read the Status Byte Register and Service Request Enable Register are listed in Table 11-3. For details on programming and reading registers, see “Programming enable registers,”...
Page 162: Status Register Sets
Model 2520 User’s Manual Status Structure 11-11 Status register sets As shown in Figure 11-1, there are four status register sets in the status structure of the Model 2520: Standard Event Status, Operation Event Status, Measurement Event Status, and Questionable Event Status. NOTE Appendix B for details on which register bits are set by speciﬁc error and...
Page 163 11-12 Status Structure Model 2520 User’s Manual Figure 11-4 Standard event status — — Standard Event *ESR? (B15 Status Register –B8) (B7) (B6) (B5) (B4) (B3) (B2) (B1) (B0) & & & & & & & To Event *ESE — —...
Page 164: Operation Event Register
Model 2520 User’s Manual Status Structure 11-13 Operation event register The used bits of the Operation Event Register (shown in Figure 11-5) are described as fol- lows: • Bit B0, Calibrating (Cal) — Set bit indicates that the Model 2520 is calibrating. •...
Page 165: Measurement Event Register
11-14 Status Structure Model 2520 User’s Manual Measurement event register The used bits of the Measurement Event Register (shown in Figure 11-6) are described as follows: • Bit B0 — Not used. • Bit B1, HW Interlock (INT) — Set bit indicates that the hardware interlock line on the testhead is at a digital low (asserted).
Page 166 Model 2520 User’s Manual Status Structure 11-15 Figure 11-6 Measurement event status Measurement Condition Register stat:meas:cond? — (B4) (B15) (B9) (B8) (B7) (B6) (B5) (B3) (B2) (B1) (B0) (B14) (B11) (B10) (B13) (B12) stat:meas? — (B4) (B15) (B9) (B8) (B7) (B6) (B5) (B3) (B2)
Page 167: Questionable Event Register
11-16 Status Structure Model 2520 User’s Manual Questionable event register The used bits of the Questionable Event Register (shown in Figure 11-7) are described as follows: • Bits B0 through B7 — Not used. • Bit B8, Calibration Summary (Cal) — Set bit indicates that an invalid calibration constant was detected during the power-up sequence.
Page 168: Condition Registers
Model 2520 User’s Manual Status Structure 11-17 Condition registers Figure 11-1 shows, each status register set (except the Standard Event Register set) has a condition register. A condition register is a real-time, read-only register that constantly updates to reﬂect the present operating conditions of the instrument. For example, while the Model 2520 is in the idle state, bit B10 (Idle) of the Operation Condition Register will be set.
Page 169: Event Enable Registers
11-18 Status Structure Model 2520 User’s Manual Event enable registers Figure 11-1 shows, each status register set has an enable register. Each event register bit is logically ANDed (&) to a corresponding enable bit of an enable register. Therefore, when an event bit is set and the corresponding enable bit is set (as programmed by the user), the output (summary) of the register will set to 1, which in turn sets the summary bit of the Status Byte Register.
Page 170: Programming Example - Program And Read Register Set
Model 2520 User’s Manual Status Structure 11-19 Programming example - program and read register set The command sequence in Table 11-8 programs and reads the measurement register set. Registers are read using the binary format (which directly indicates which bits are set). The command to select format (FORMat:SREGister) is documented in Table 11-2.
Page 171: Error Queue
11-20 Status Structure Model 2520 User’s Manual Error queue The Error Queue holds error and status messages. When an error or status event occurs, a message that deﬁnes the error/status is placed in the Error Queue. When a message is placed in the Error Queue, the Error Available (EAV) bit in the Status Byte Register is set.
Page 172: Programming Example - Read Error Queue
Model 2520 User’s Manual Status Structure 11-21 Table 11-9 Error queue commands Command Description Default STATus STATus Subsystem: :QUEue Read Error Queue: Note 1 [:NEXT]? Read and clear oldest error/status (code and message). :ENABle <list> Specify error and status messages for Error Queue. Note 2 :ENABle? Read the enabled messages.
Page 173: Common Commands
Common Commands • Command summary — Lists the IEEE-488.2 common commands used by the Model 2520. • Command reference — Provides a detailed reference for all common commands except for those associated with the status structure, which are discussed in Section...
Page 174: Command Summary
12-2 Common Commands Model 2520 User’s Manual Command summary Common commands (summarized in Table 12-1) are device commands that are common to all devices on the bus. These commands are designated and deﬁned by the IEEE-488.2 standard. Most of these commands are described in detail in this section. NOTE The following common commands associated with the status structure are cov- ered in...
Page 175: Command Reference
Model 2520 User’s Manual Common Commands 12-3 Command reference *IDN? — identiﬁcation query Reads identiﬁcation code The identiﬁcation code includes the manufacturer, model number, serial number, and ﬁrm- ware revision levels and is sent in the following format: KEITHLEY INSTRUMENTS INC., MODEL 2520, xxxxxxx, yyyyyyy, zzzzz mmm ddd yyyy ++:++:++ /aaa/bbb/c/d/e Where: xxxxxxx is the mainframe serial number.
Page 176: Opc Programming Example
12-4 Common Commands Model 2520 User’s Manual *OPC programming example The command sequence in Table 12-2 will perform 10 measurements. After the measure- ments are completed (in approximately 10 seconds), an ASCII “1” will be placed in the Output Queue and displayed on the computer CRT. Note that additional codes must be added to query the instrument for the presence of the ASCII “1”...
Page 177: Sav, *Rcl Programming Example
Model 2520 User’s Manual Common Commands 12-5 *SAV, *RCL programming example Table 12-3 summarizes the basic command sequence for saving and recalling a setup. The present setup is stored in memory location 2, GPIB defaults are restored, and the memory location 2 setup is recalled.
Page 178: Tst? - Self-Test Query
12-6 Common Commands Model 2520 User’s Manual Table 12-4 *TRG programming example Command Description *RST Restore GPIB defaults. :TRIG:SOUR BUS Select BUS trigger control source. :TRIG:COUN INF Set trigger layer count to inﬁnite. :OUTP1 ON Turn on output. :INIT Take Model 2520 out of idle. *TRG Trigger one measurement.
Page 179: Scpi Signal-Oriented Measurement Commands
SCPI Signal-Oriented Measurement Commands • Command summary — Summarizes those commands used to acquire readings. • Acquiring readings — Describes commands to acquire post-processed readings, both trigger and acquire readings, and to perform a single measurement.
Page 180: Command Summary
13-2 SCPI Signal-Oriented Measurement Commands Model 2520 User’s Manual Command summary The signal-oriented measurement commands are used to acquire readings. You can use these high-level instructions to control the measurement process. These commands are summarized in Table 13-1. Table 13-1 Signal-oriented measurement command summary Command Description...
Page 181: [:Sense[1]]:Data[:Latest]
Model 2520 User’s Manual SCPI Signal-Oriented Measurement Commands 13-3 NOTE Appendix C for a detailed explanation on how data ﬂows through the vari- ous operation blocks of the Model 2520. It clariﬁes the types of readings that are acquired by the various commands to read data. [:SENSe[1]]:DATA[:LATest]? [:SENSe2]:DATA[:LATest]? [:SENSe3]:DATA[:LATest]?
Page 182: Scpi Command Reference
SCPI Command Reference • Reference tables — Summarizes each SCPI command subsystem. • SCPI subsystems — Provides detailed information on all commands in each SCPI subsystem.
Page 183: Reference Tables
14-2 SCPI Command Reference Model 2520 User’s Manual Reference tables Table 14-1 through Table 14-10 summarize the commands for each SCPI subsystem. The following list includes the SCPI subsystem commands and the table number where each command is summarized. Summary table Subsystem Function(s) 14-1...
Page 184 Model 2520 User’s Manual SCPI Command Reference 14-3 Table 14-1 CALCulate command summary Default Command Description parameter SCPI :CALCulate[1] Path to conﬁgure and control laser diode math: :DATA Path to CALC1 data. :LATest? Return only most recent math result. :DATA? Read result of math generated by INIT.
Page 185 14-4 SCPI Command Reference Model 2520 User’s Manual Table 14-1 (continued) CALCulate command summary Default Command Description parameter SCPI :CALCulate3 Path to conﬁgure and control detector #2 math: :DATA Path to CALC3 data. :LATest? Return only most recent math result. :DATA? Read result of math generated by INIT.
Page 186 Model 2520 User’s Manual SCPI Command Reference 14-5 Table 14-2 DISPlay command summary Default Command Description parameter SCPI :DISPlay :ENABle Turn on or turn off front panel display. Note 1 :ENABle? Query state of display. [:WINDow[1]] Path to locate message to top display line: :TEXT Control user test message: Note 2...
Page 187 14-6 SCPI Command Reference Model 2520 User’s Manual Table 14-3 FORMat command summary Default Command Description parameter SCPI :FORMat :SREGister <name> Select data format for reading status event registers (ASCii, HEXadecimal, OCTal, or BINary). :SREGister? Query format for reading status event registers. [:DATA] <type>[<,length>] Specify data format (ASCii, REAL, 32, or SREal).
Page 188 Model 2520 User’s Manual SCPI Command Reference 14-7 Table 14-5 SENSe command summary Default Command Description parameter SCPI [:SENSe[1]] Sense 1 subsystem to control laser diode voltage measurement: :VOLTage[:DC] Path to conﬁgure voltage: :RANGe Conﬁgure measurement range: [:UPPer] <n> Select range by specifying the expected voltage reading; 0 to 10.5 (Ranges 5 or 10).
Page 189 14-8 SCPI Command Reference Model 2520 User’s Manual Table 14-5 (continued) SENSe command summary Default Command Description parameter SCPI :SENSe3 Sense 3 subsystem to control detector #2 current measurement: :CURRent[:DC] Path to conﬁgure current: :RANGe Conﬁgure measurement range: [:UPPer] <n> Select range by specifying the expected current reading;...
Page 190 Model 2520 User’s Manual SCPI Command Reference 14-9 Table 14-6 SOURce command summary Default Command Description parameter SCPI :SOURce[1] Path to control laser diode current source: :CLEar[:IMMediate] Turn all three sources off. :CURRent Path to conﬁgure current: :MODE <name> Select mode (FIXed, SWEep, or LIST). :MODE? Query mode.
Page 191 14-10 SCPI Command Reference Model 2520 User’s Manual Table 14-6 (continued) SOURce command summary Default Command Description parameter SCPI :SOURce[1] Path to control laser diode current source (continued): :VOLTage Path to set compliance level. :PROTection [:LEVel] <NRf> Set voltage limit; 3 to 10.5. [:LEVel]? Query voltage limit.
Page 192 Model 2520 User’s Manual SCPI Command Reference 14-11 Table 14-6 (continued) SOURce command summary Default Command Description parameter SCPI :SOURce2 Path to control detector #1 voltage bias source: :VOLTage [:LEVel] Set source level (in volts): [:IMMediate] Set speciﬁed voltage level immediately: [:AMPLitude] <n>...
Page 193 14-12 SCPI Command Reference Model 2520 User’s Manual Table 14-7 STATus command summary Default Command Description parameter SCPI :STATus Note 1 :MEASurement Control measurement event registers: [:EVENt]? Read the event register. Note 2 :ENABle <NDN> Program the enable register. Note 3 or <NRf>...
Page 194 Model 2520 User’s Manual SCPI Command Reference 14-13 Table 14-8 SYSTem command summary Default Command Description parameter SCPI :SYSTem :PRESet Return to :SYSTem:PRESet defaults. :POSetup <name> Select power-on setup (RST, PRESet or SAV 0-4). :POSetup? Query power-on setup. :VERSion? Query revision level of SCPI. :ERRor Path to read messages in error queue.
Page 195: Calculate Subsystems
14-14 SCPI Command Reference Model 2520 User’s Manual Table 14-10 TRIGger command summary Default Command Description parameter SCPI :INITiate[:IMMediate] Initiate source and measure cycle(s). :ABORt Reset trigger system. Goes to idle state. :TRIGger Path to program Trigger Layer: [:SEQuence[1]] [:LAYer[1]] :COUNt <n>...
Page 196: Select Laser Diode Math Function
Model 2520 User’s Manual SCPI Command Reference 14-15 Select laser diode math function FORMat <name> :CALCulate[1]:FORMat <name> Select laser diode math function Parameters <name> = MXB[1] MX + B CONDuctance[1] I1/V1 V1 × I1 POWER[1] RESistance[1] V1/I1 Query :FORMat? Query selected math function Description This command selects the laser diode math function.
Page 197: Units
14-16 SCPI Command Reference Model 2520 User’s Manual Query :MMFactor? Query M (slope) value for MX + B Description These commands program the M (slope) value for the MX + B math function. Use CALC1 for the laser diode, CALC2 for detector #1, and CALC3 for detector #2.

Page 198: Data
Model 2520 User’s Manual SCPI Command Reference 14-17 DATA? :CALCulate[1]:DATA? Read laser diode math (CALC1) result :CALCulate2:DATA? Read detector #1 math (CALC2) result :CALCulate3:DATA? Read detector #2 math (CALC3) result :CALCulate4:DATA? Read delta math (CALC4) result Description These query commands are used to read the result of the CALC1, CALC2, CALC3, or CALC4 calculation.
Page 199: Attributes
14-18 SCPI Command Reference Model 2520 User’s Manual ATTRibutes? :DISPlay[:WINDow[1]]:ATTRibutes? Query attributes; top display :DISPlay:WINDow2:ATTRibutes? Query attributes; bottom display Description These query commands are used to determine which characters on the display are blinking and which are not. The response message provides that status of each character position for the speciﬁed display.
Page 200: State
Model 2520 User’s Manual SCPI Command Reference 14-19 An indeﬁnite block message must be the only command in the program message or the last command in the program message. If you include a command after an indeﬁnite block message (on the same line), it will be treated as part of the message and is displayed instead of executed.

Page 201 14-20 SCPI Command Reference Model 2520 User’s Manual Description This command is used to select the data format for transferring readings over the bus. Only the ASCII format is allowed over the RS-232 inter- face. This command only affects the output of READ?, FETCh?, MEA- Sure?, TRACe:DATA?, CALCx:DATA? over the GPIB.
Page 202 Model 2520 User’s Manual SCPI Command Reference 14-21 Figure 14-2 IEEE-754 single precision data format (32 data bits) Header Byte 1 Byte 2 Byte 3 Byte 4 s = sign bit (0 = positive, 1 = negative) e = exponent bits (8) f = fraction bits (23) Normal byte order shown.
Page 203: Data Elements
14-22 SCPI Command Reference Model 2520 User’s Manual Data elements ELEMents <item list> :FORMat:ELEMents [SENSe] <item list> Specify data elements for data string Parameters <item list> = CURRent[1] Includes laser diode source value CURRent2 Includes detector #1 current reading CURRent3 Includes detector #2 current reading VOLTage[1] Includes laser diode voltage reading...
Page 204: Calculate Data Elements
Model 2520 User’s Manual SCPI Command Reference 14-23 VOLTage3 — This element provides the detector #2 voltage source value. TIME — A timestamp is available to reference each group of readings to a point in time. The relative timestamp operates as a timer that starts at zero seconds when the instrument is turned on or when the relative timestamp is reset (:SYSTem:TIME:RESet).
Page 205: Trace Data Elements
14-24 SCPI Command Reference Model 2520 User’s Manual Description This command is used to specify the data elements returned by the CALCn:DATA? and CALCn:DATA:LATest? queries. You can specify from one to all three elements. Each element in the list must be separated by a comma (,). These elements are explained as fol- lows: NOTE An overﬂow reading reads as +9.9E37.
Page 206: Source4
Model 2520 User’s Manual SCPI Command Reference 14-25 CURRent2 — This element provides the detector #1 current reading. If no current reading is available, the NAN (not a number) value of +9.91e37 is used. CURRent3 — This element provides the detector #2 current reading. If no current reading is available, the NAN (not a number) value of +9.91e37 is used.

Page 207: Status Register Format
14-26 SCPI Command Reference Model 2520 User’s Manual The “#0” header is not affected by this command. The header is always sent at the beginning of the data string for each measurement conver- sion. The ASCII data format can only be sent in the normal byte order. The SWAPped selection is simply ignored when the ASCII format is selected.
Page 208: Output Subsystem
Model 2520 User’s Manual SCPI Command Reference 14-27 OUTPut subsystem This subsystem is used to control the three source outputs and query the state of the inter- lock. These commands are summarized in Table 14-4. Turn sources on or off [:STATe] ...
Page 209: Select Laser Diode Voltage Measurement Range
14-28 SCPI Command Reference Model 2520 User’s Manual Select laser diode voltage measurement range [:UPPer] <n> [:SENSe[1]]:VOLTage[:DC]:RANGe[:UPPer] <n>|UP|DOWN Select laser diode voltage range Parameters <n> = 0 to 10.5 Expected reading in volts DEFault MINimum MAXimum 10.5 Select next higher measurement range DOWN Select next lower measurement range Query...
Page 210: Select Polarity
Model 2520 User’s Manual SCPI Command Reference 14-29 Description These commands are used to select the current measurement range for detector #1 and detector #2. The range is selected by specifying the expected reading. The instrument will then go to the most sensitive reading that will accommodate that reading.
Page 211: Query Latest Readings
14-30 SCPI Command Reference Model 2520 User’s Manual Query latest readings [:LATest]? [:SENSe[1]]:DATA[:LATest]? Query laser diode voltage reading :SENSe2:DATA[:LATest]? Query detector #1 current reading :SENSe3:DATA[:LATest]? Query detector #3 current reading Query :DATA[:LATest]? Query latest reading Description These queries request the latest readings only when the unit is in the idle layer of the trigger model (see Section 8 for triggering information).
Page 212: [:State]
Model 2520 User’s Manual SCPI Command Reference 14-31 [:STATe] [:SENSe[1]]:AVERage:[:STATe] Enable/disable digital ﬁlter :SENSe2:AVERage:[:STATe] Enable/disable digital ﬁlter :SENSe3:AVERage:[:STATe] Enable/disable digital ﬁlter Parameters = 0 or OFF Disable digital ﬁlter 1 or ON Enable digital ﬁlter Query [:STATe]? Query state of average digital ﬁlter...

Page 213: Source Subsystem
14-32 SCPI Command Reference Model 2520 User’s Manual SOURce subsystem This subsystem is used to conﬁgure and control the laser diode current source, the two detector voltage bias sources, and to set the logic level (high or low) of each digital output line.
Page 214: Select Source Function
Model 2520 User’s Manual SCPI Command Reference 14-33 NOTE The sourcing mode will default to FIXed whenever the Model 2520 goes to the local state. Select source function FUNCtion[:SHAPe] <name> :SOURce[1]:FUNCtion[:SHAPe] <name> Select laser diode source function Parameters <name> = Select DC source function PULSe Select pulse source function...
Page 215: Set Amplitudes
14-34 SCPI Command Reference Model 2520 User’s Manual For example, if you expect to source levels around 300mA, send the fol- lowing command: :SOURce1:CURRent:RANGe 0.3 The above command will select the 500mA range for the laser diode current source. As listed in Parameters, you can also use the MINimum, MAXimum and DEFault parameters to manually select the source range.
Page 216: Set Voltage Limit
Model 2520 User’s Manual SCPI Command Reference 14-35 Query :LOW? Query programmed low amplitude :LOW? DEFault Query *RST default low amplitude :LOW? MINimum Query lowest allowable low amplitude :LOW? MAXimum Query highest allowable low amplitude Description This command is used to set the pulse low amplitude level for all current source pulses.
Page 217: Set Pulse Times
14-36 SCPI Command Reference Model 2520 User’s Manual Set pulse times DELay <n> :SOURce[1]:PULSe:DELay <n> Set current source pulse delay Parameters <n> = 20e-6 to 0.5 Specify pulse delay in seconds MINimum 20e-6 seconds MAXimum 0.5 seconds DEFault 10e-3 seconds Query :DELay? Query pulse delay...
Page 218: Configure Sweeps
Model 2520 User’s Manual SCPI Command Reference 14-37 Conﬁgure sweeps There are two methods to conﬁgure the start and stop levels of a sweep. You can use either the :STARt and :STOP commands or you can use the :CENTer and :SPAN commands. See “Sweep and list program examples,”...
Page 219: Center
14-38 SCPI Command Reference Model 2520 User’s Manual Description These commands are used to specify the start and stop levels for a sweep. When the sweep is started, the source will output the speciﬁed start level and measurements are performed. The sweep continues until the source outputs the speciﬁed stop level.

Page 220: Step
Model 2520 User’s Manual SCPI Command Reference 14-39 :CENTer and :SPAN are coupled to STARt and :STOP. Thus, when cen- ter and span values are changed, the values for start and stop are affected as follows: Start = Center - (Span / 2) Stop = Center + (Span / 2) STEP <n>...

Page 221: Points
14-40 SCPI Command Reference Model 2520 User’s Manual POINts <n> :SOURce[1]:SWEep:POINts <n> Set number of points for sweep Parameters <n> = 2 to 1000 Specify number of source-measure points MINimum MAXimum 1000 DEFault 1000 Query :POINts? Query number of sweep points :POINts? DEFault Query *RST default number of sweep points :POINts? MINimum...

Page 222: Configure List
Model 2520 User’s Manual SCPI Command Reference 14-41 This command lets you change the execution direction of the sweep. With DOWN selected, the sweep will begin at the stop level and end at the start level. Selecting UP restores sweep operation to the normal start to stop direction.
Page 223: Points
14-42 SCPI Command Reference Model 2520 User’s Manual POINts? :SOURce[1]:LIST:CURRent:POINts? Query length of current list Description These commands are used to determine the length of the speciﬁed cur- rent list. The response message indicates the number of source values in the list.
Page 224: Delay
Model 2520 User’s Manual SCPI Command Reference 14-43 DELay <NRf list> :SOURce[1]:LIST:DELay <NRf list> Deﬁne pulse delay list Parameters <NRf list> = NRf, NRf … NRf NRf = 20e-6 to 0.5 Pulse delay (seconds) Query :DELay? Query pulse delay list Description This command is used to deﬁne a list of pulse delays (up to 100) for the list sourcing mode of operation.

Page 225: Sweep And List Program Examples
14-44 SCPI Command Reference Model 2520 User’s Manual Sweep and list program examples Linear staircase sweep Linear current sweep from 10mA to 100mA in 10mA increments: *RST SOUR1:SWE:SPAC LIN SOUR1:CURR:STAR 10e-3 SOUR1:CURR:STOP 100e-3 SOUR1:CURR:STEP 10e-3 SOUR1:SWE:POIN? (returns 10) SOUR1:CURR:MODE SWE OUTP1 ON INIT List sweep...
Page 226: Logarithmic Staircase Sweep
Model 2520 User’s Manual SCPI Command Reference 14-45 Logarithmic staircase sweep Logarithmic staircase sweep from 10mA to 100mA in 20 points: *RST SOUR1:SWE:SPAC LOG SOUR1:CURR:STAR 10e-3 SOUR1:CURR:STOP 100e-3 SOUR1:SWE:POIN 20 SOUR1:CURR:MODE SWE OUTP1 ON INIT To determine the current source values that will be generated: Start: (Start): Stop:...
Page 227: Source2 And Source3
14-46 SCPI Command Reference Model 2520 User’s Manual Now add the LogStep value to Log (Start) and to each subsequent result. This will create a list of Log Values. Next take the anti-log of each Log Value to get the actual sweep values: Value# Value...
Page 228: Set Amplitudes
Model 2520 User’s Manual SCPI Command Reference 14-47 Set amplitudes [:IMMediate][:AMPLitude] <n> :SOURce2:VOLTage[:LEVel][IMMediate][:AMPLitude] <n> Set detector #1 source amplitude :SOURce3:VOLTage[:LEVel][IMMediate][:AMPLitude] <n> Set detector #2 source amplitude Parameters <n> = -20 to 20 Set source amplitude (volts) DEFault MINimum -20V MAXimum Query :VOLTage? Query programmed source amplitude...
Page 229: Setting Bit Size
14-48 SCPI Command Reference Model 2520 User’s Manual Description This command is used to set the logic levels of the output lines of the Digital I/O port. When set high, the speciﬁed output line will be at approximately +5V. When set low, the output line will be at 0V. Use the following table to determine the parameter value for the desired decimal digital output pattern: Decimal...
Page 230: Status Subsystem
Model 2520 User’s Manual SCPI Command Reference 14-49 STATus subsystem The STATus subsystem is used to control the status registers of the Model 2520. The com- mands in this subsystem are summarized in Table 14-7. NOTE These registers and the overall status structure are fully explained in Section Read event registers [:EVENt]?
Page 231: Read Condition Registers
14-50 SCPI Command Reference Model 2520 User’s Manual Read condition registers CONDition? :STATus:MEASurement:CONDition? Read Measurement Condition :STATus:QUEStionable:CONDition? Read Questionable Register :STATus:OPERation:CONDition? Read Operation Condition Description These query commands are used to read the contents of the condition registers. Select default conditions PRESet :STATus:PRESet Return registers to default conditions...
Page 232: Enable
Model 2520 User’s Manual SCPI Command Reference 14-51 ENABle <list> :STATus:QUEue:ENABle <list> Enable messages for Error Queue Parameters <list> = (numlist) where numlist is a speciﬁed list of messages that you wish to enable for the Error. Query :ENABle? Query list of enabled messages Description On power-up, all error messages are enabled and will go into the Error Queue as they occur.

Page 233: Posetup
14-52 SCPI Command Reference Model 2520 User’s Manual POSetup :SYSTem:POSetup <name> Program power-on defaults Parameters <name> = Power-up to *RST defaults PRESet Power-up to :SYSTem:PRESet defaults SAV0 Power-up to setup stored at memory location 0 SAV1 Power-up to setup stored at memory location 1 SAV2 Power-up to setup stored at memory location 2 SAV3...
Page 234: Count
Model 2520 User’s Manual SCPI Command Reference 14-53 COUNt? :SYSTem:ERRor:COUNt? Return the number of errors Description After sending this command and addressing the Model 2520 to talk, a decimal number will be sent to the computer. That is the number of mes- sages in the Error Queue.
Page 235: Read Version Of Scpi Standard
14-54 SCPI Command Reference Model 2520 User’s Manual LASER V MATH key RANGE ENTER key DETECTOR 2 I TRIG key SETUP key LASER I LOCAL key ON/OFF OUTPUT key ----- EDIT SWEEP key CONFIG key DETECTOR 1 V RECALL key PW key Query :KEY?
Page 236: Rs-232 Interface
Model 2520 User’s Manual SCPI Command Reference 14-55 RS-232 interface NOTE The following commands are intended for use over the RS-232 interface, but they can also be used over the GPIB. LOCal :SYSTem:LOCal Take Model 2520 out of remote Description Normally, during RS-232 communications, front panel keys are opera- tional.
Page 237: Trace Subsystem
14-56 SCPI Command Reference Model 2520 User’s Manual TRACe subsystem The TRACe subsystem is mostly a diagnostic tool for debugging connections and setup. In normal operation, a 14-bit A/D converter in the Model 2520 samples at 10MHz rate, and then, an internal Digital Signal Processor (DSP) interprets the A/D samples over the pulse width in order to determine the pulse level value, or a DC average, which are then sent back to the user.
Page 238: Configure Sample Buffer
Model 2520 User’s Manual SCPI Command Reference 14-57 Conﬁgure sample buffer POINts <n> :TRACe:POINts <n> Specify number of samples Parameters <n> = 1 to 3000 Specify number of samples MINimum MAXimum 32000 DEFault Query :POINts? Query number of samples :POINts? MINimum Query smallest allowable sample number :POINts? MAXimum Query largest allowable sample number...
Page 239: Abort Source/Measure Cycle
14-58 SCPI Command Reference Model 2520 User’s Manual Abort source/measure cycle ABORt Abort operation Description When this action command is sent, the Model 2520 aborts operation and returns to the idle state. A faster way to return to idle is to use the DCL or SDC command. Program trigger model COUNt <n>...
Page 240: Timer
Model 2520 User’s Manual SCPI Command Reference 14-59 Query :SOURce? Query programmed control source Description This command is used to select the event control source. With IMMedi- ate selected, operation immediately continues. A speciﬁc event can be used to control operation. With TLINk selected, operation continues when a trigger pulse is received via the Trigger Link.

Page 241: Iline
14-60 SCPI Command Reference Model 2520 User’s Manual ILINe <NRf> :TRIGger[:SEQuence[1]][:TCONﬁgure]:ILINe <NRf> Select Trigger Link input line Parameters <NRf> = Line #1 Line #2 Line #3 Line #4 Line #5 Line #6 Query :ILINe? Query input trigger line Description This command is used to select input lines for the Trigger Link. For nor- mal operation, Trigger Link input and output (see “OLINe <NRf>”)

Page 242: Specifications
Speciﬁcations Refer to www.tek.com/keithley for the latest specifications.
Page 243 Specifications Model 2520 User’s Manual Accuracy calculations The following information discusses how to calculate accuracy for both measurement and source functions. Measurement accuracy Measurement accuracy is calculated as follows: Accuracy = ±(% of reading + offset) As an example of how to calculate the actual reading limits, assume that you are measur- ing 5V on the 10V laser diode measurement range.
Page 244: Status And Error Messages
Status and Error Messages...
Page 245: Introduction
Status and Error Messages Model 2520 User’s Manual Introduction This Appendix contains a summary of status and error messages, which status register bits are set when messages occur, and methods to avoid or eliminate most common SCPI errors. Status and error messages Table B-1 summarizes status and error messages, which are stored in the Error Queue.
Page 246 Model 2520 User’s Manual Status and Error Messages Table B-1 Status and error messages Number Error message Event Status register -440 Query UNTERMINATED after Standard Event indeﬁnite response -430 Query DEADLOCKED Standard Event -420 Query UNTERMINATED Standard Event -410 Query INTERRUPTED Standard Event -363 Input buffer overrun...
Page 247 Status and Error Messages Model 2520 User’s Manual Table B-1 (continued) Status and error messages Number Error message Event Status register -178 Expression data not allowed Standard Event -171 Invalid expression Standard Event -170 Expression error Standard Event -168 Block data not allowed Standard Event -161 Invalid block data...
Page 248 Model 2520 User’s Manual Status and Error Messages Table B-1 (continued) Status and error messages Number Error message Event Status register Measurement events: +101 Hardware interlock asserted Measurement Event +102 Laser diode measurement overﬂow Measurement Event +103 Detector 1 measurement overﬂow Measurement Event +104 Detector 2 measurement overﬂow...
Page 249 Status and Error Messages Model 2520 User’s Manual Table B-1 (continued) Status and error messages Number Error message Event Status register Lost data errors: +601 Reading buffer data lost Standard Event +602 GPIB address lost Standard Event +603 Power-on state lost Standard Event +604 Calibration data lost...
Page 250: Eliminating Common Scpi Errors
Model 2520 User’s Manual Status and Error Messages Eliminating common SCPI errors There are three SCPI errors that occur more often than any others: • -113, "Undeﬁned header" • -410, "Query INTERRUPTED" • -420, "Query UNTERMINATED" The following paragraphs discuss the most common causes for these errors and methods for avoiding them.
Page 251: 420, "Query Unterminated
Status and Error Messages Model 2520 User’s Manual • Incorrectly conﬁgured IEEE-488 driver. The driver must be conﬁgured so that when talking on the bus it sends line-feed with EOI as the terminator, and when lis- tening on the bus it expects line-feed with EOI as the terminator. See the reference manual for your particular IEEE-488 interface.
Page 252: Data Flow
Data Flow...
Page 253: Introduction
Data Flow Model 2520 User’s Manual Introduction Data ﬂow for remote operation is summarized by the block diagram shown in Figure C-1. Refer to this block diagram for the following discussion. Figure C-1 Data ﬂow block diagram CALC1:DATA? DATA? Bypass if Three Independent CALC1 Simultaneous 10MHz...
Page 254: Sens1, Sens2, And Sens3
Model 2520 User’s Manual Data Flow SENS1, SENS2, and SENS3 The SENS1 block represents the basic laser diode voltage readings. The SENS2 and SENS3 blocks represent the basic measured current readings for photodiode detector #1 and photodiode detector #2 respectively. If the ﬁlter is enabled, the readings will be ﬁl- tered.
Page 255: Read? And Measure
Data Flow Model 2520 User’s Manual READ? and MEASure? The READ? and MEASure? commands perform an INITiate and then a FETCh? The INITiate command triggers a new source and measure cycle which puts new data in the reading buffer after processing by the DSP. FETCh? reads that new processed data. See Section 13 for more information on READ? and MEASure?.
Page 256: Ieee-488 Bus Overview
IEEE-488 Bus Overview...
Page 257: Introduction
IEEE-488 Bus Overview Model 2520 User’s Manual Introduction Basically, the IEEE-488 bus is a communication system between two or more electronic devices. A device can be either an instrument or a computer. When a computer is used on the bus, it serves to supervise the communication exchange between all the devices and is known as the controller.
Page 258 Model 2520 User’s Manual IEEE-488 Bus Overview talker sends data while a listener receives data. Depending on the type of instrument, any particular device can be a talker only, a listener only, or both a talker and listener. There are two categories of controllers: system controller and basic controller. Both are able to control other instruments, but only the system controller has the absolute authority in the system.
Page 259 IEEE-488 Bus Overview Model 2520 User’s Manual Figure D-1 IEEE-488 bus conﬁguration To Other Devices Device 1 Able to Talk, Listen and Control (Computer) Data Bus Device 2 Able to Talk and Data Byte Listen Transfer (2520) Control Device 3 Only Able to Listen General...
Page 260: Bus Lines
Model 2520 User’s Manual IEEE-488 Bus Overview Bus lines The signal lines on the IEEE-488 bus are grouped into three different categories: data lines, management lines, and handshake lines. The data lines handle bus data and com- mands, while the management and handshake lines ensure that proper data transfer and operation takes place.
Page 261 IEEE-488 Bus Overview Model 2520 User’s Manual NRFD (Not Ready For Data) — The acceptor controls the state of NRFD. It is used to signal to the transmitting device to hold off the byte transfer sequence until the accepting device is ready. NDAC (Not Data Accepted) —...
Page 262: Bus Commands
Model 2520 User’s Manual IEEE-488 Bus Overview Bus commands The instrument may be given a number of special bus commands through the IEEE-488 interface. This section brieﬂy describes the purpose of the bus commands which are grouped into the following four categories. Uniline commands —...
Page 263: Uniline Commands
IEEE-488 Bus Overview Model 2520 User’s Manual Uniline commands ATN, IFC and REN are asserted only by the controller. SRQ is asserted by an external device. EOI may be asserted either by the controller or other devices depending on the direction of data transfer.
Page 264: Addressed Multiline Commands
Model 2520 User’s Manual IEEE-488 Bus Overview Addressed multiline commands Addressed commands are multiline commands that must be preceded by the device listen address before that instrument will respond to the command in question. Note that only the addressed device will respond to these commands. Both the commands and the address preceding it are sent with ATN true.
Page 265: Common Commands
D-10 IEEE-488 Bus Overview Model 2520 User’s Manual Common commands Common commands are commands that are common to all devices on the bus. These com- mands are designated and deﬁned by the IEEE-488.2 standard. Generally, these commands are sent as one or more ASCII characters that tell the device to perform a common operation, such as reset.
Page 266: Command Codes
Model 2520 User’s Manual IEEE-488 Bus Overview D-11 Figure D-3 Command codes...
Page 267: Typical Command Sequences
D-12 IEEE-488 Bus Overview Model 2520 User’s Manual Typical command sequences For the various multiline commands, a speciﬁc bus sequence must take place to properly send the command. In particular, the correct listen address must be sent to the instrument before it will respond to addressed commands.
Page 268: Ieee Command Groups
Model 2520 User’s Manual IEEE-488 Bus Overview D-13 IEEE command groups Command groups supported by the Model 2520 are listed in Table D-5. Common com- mands and SCPI commands are not included in this list. Table D-5 IEEE command groups HANDSHAKE COMMAND GROUP NDAC = NOT DATA ACCEPTED NRFD = NOT READY FOR DATA...
Page 269: Interface Function Codes
D-14 IEEE-488 Bus Overview Model 2520 User’s Manual Interface function codes The interface function codes, which are part of the IEEE-488 standards, deﬁne an instru- ment's ability to support various interface functions and should not be confused with pro- gramming commands found elsewhere in this manual. The interface function codes for the Model 2520 are listed in Table D-6.
Page 270 Model 2520 User’s Manual IEEE-488 Bus Overview D-15 PP (Parallel Poll Function) — The instrument does not have parallel polling capabilities (PP0). DC (Device Clear Function) — DC1 deﬁnes the ability of the instrument to be cleared (initialized). DT (Device Trigger Function) — DT1 deﬁnes the ability of the Model 2520 to have readings triggered.
Page 271 IEEE-488 and SCPI Conformance Information...
Page 272: Ieee-488 And Scpi Conformance Information
IEEE-488 and SCPI Conformance Information Model 2520 User’s Manual Introduction The IEEE-488.2 standard requires speciﬁc information about how the Model 2520 imple- ments the standard. Paragraph 4.9 of the IEEE-488.2 standard (Std 488.2-1987) lists the documentation requirements. Table E-1 provides a summary of the requirements, and pro- vides the information or references the manual for that information.
Page 273 Model 2520 User’s Manual IEEE-488 and SCPI Conformance Information Table E-1 IEEE-488 documentation requirements Requirements Description or reference IEEE-488 Interface Function Codes. Appendix Behavior of Model 2520 when the address is set outside Cannot enter an invalid address. the range 0-30. Behavior of Model 2520 when valid address is entered.
Page 274 IEEE-488 and SCPI Conformance Information Model 2520 User’s Manual Table E-2 Coupled commands Command Also changes :SOURce[1]:CURRent:STARt :SOURce[1]:CURRent:STEP :SOURce[1]:CURRent:CENTer :SOURce[1]:CURRent:SPAN :SOURce[1]:CURRent:STOP :SOURce[1]:CURRent:STEP :SOURce[1]:CURRent:CENTer :SOURce[1]:CURRent:SPAN :SOURce[1]:CURRent:STEP :SOURce[1]:CURRent:POINts :SOURce[1]:CURRent:POINts :SOURce[1]:CURRent:STEP :SOURce[1]:CURRent:CENTer :SOURce[1]:CURRent:STARt :SOURce[1]:CURRent:STOP :SOURce[1]:CURRent:STEP :SOURce[1]:CURRent:SPAN :SOURce[1]:CURRent:STARt :SOURce[1]:CURRent:STOP :SOURce[1]:CURRent:STEP :SOURce[1]:PULSe:WIDTh ;SOURce[1]:PULSe:DELay :TRACe:POINts :SOURce[1]:PULSe:DELay :SOURce[1]:PULSe:WIDTh :SOURce[1]:PULSe:TRANsition:STATe :SOURce[1]:PULSe:WIDTh...
Page 275: Measurement Considerations
Measurement Considerations...
Page 276: Optimizing Laser Diode Connections
Measurement Considerations Model 2520 User’s Manual Optimizing laser diode connections There are several key considerations when making connections to the laser diode: • Cable length and inductance • Exposed loop area • Correct sense lead connections • Magnetic coupling between sense and current leads Each of these considerations is discussed in detail below.
Page 277: Cable Inductance
Model 2520 User’s Manual Measurement Considerations Cable inductance Under transient conditions, the voltage across the cable inductance is deﬁned as follows: ---- - Where: = total cable inductance = voltage across inductance di/dt = rate of change of current For example, the voltage with 100nH of inductance, a 5A current pulse, and 100ns rise time is: -------------- - 100nH...
Page 278 Measurement Considerations Model 2520 User’s Manual A comparison of operating conditions is shown in Figure F-2 Figure F-3. Figure F-2 shows the settled response for 4A into 1.6Ω using 3m of cable. Inductance is excessive in this case, resulting in the ﬁrst settled reading at 1.7µs, as opposed to 1.5µs (a 1µs delay was used before the pulse).
Page 279: Increasing Cable Length
Model 2520 User’s Manual Measurement Considerations Figure F-3 Rise time of 0.45A current pulse 0.50 0.45 0.40 0.35 0.30 Current 0.25 0.20 0.15 0.10 0.05 0.00 Time (µs) Increasing cable length To double the effective recommended cable length without signiﬁcantly degrading pulse characteristics, connect the laser diode to the CURRENT OUTPUT HI jack only.
Page 280: Exposed Loop Area
Measurement Considerations Model 2520 User’s Manual Exposed loop area The open loop area (Figure F-4) also affects the rise time of the measurements because of added inductance. With the relatively large open loop area in Figure F-4A, the shields are not carried through to the DUT, and the exposed signal lines form a current loop.
Page 281 Model 2520 User’s Manual Measurement Considerations Figure F-5 shows ideal response of a 2A pulse for short (10 inch) properly connected cables. Figure F-6 shows the same setup except for the addition of a two square inch loop in the source connection. Figure F-5 Ideal response of 2A pulse using 10 inch cables Current...
Page 282: Sense Lead Connections
Measurement Considerations Model 2520 User’s Manual Sense lead connections Proper sense lead connections to the laser diode are important to good measurements. Figure F-7 shows a comparison of correct and incorrect sense connections. With the incor- rect connections shown in Figure F-7A, sense and current leads are not connected together at the DUT.
Page 283 Model 2520 User’s Manual Measurement Considerations Figure F-8 shows response of a 2A pulse with voltage sense leads 1/4 inch away from the DUT. Note the long settling tail corresponding to the DUT resistance (1.66Ω) and the inductance formed by the leads. Figure F-8 Response of 2A pulse with sense leads 1/4 inch away from DUT Current...
Page 284: Magnetic Coupling
F-10 Measurement Considerations Model 2520 User’s Manual Magnetic coupling Magnetic coupling between sense and current leads can also affect measurements. Figure F-9A shows connections that will result in considerable coupling due to the rela- tively long exposed signal lead area. Carrying the sense shields as close to the DUT as possible (Figure F-9B) will reduce magnetic coupling and improve response.
Page 285: Increasing Laser Diode Pulse Measurement Speed
Model 2520 User’s Manual Measurement Considerations F-11 Increasing laser diode pulse measurement speed Overview The index of refraction of a given optical media is the ratio of the speed of light in a vacuum divided by the speed of light through the media. As a ray of light passes through optical media of differing indices of refraction, reﬂections and coupling losses will result.
Page 286: Laser Diode Impedance Matching
F-12 Measurement Considerations Model 2520 User’s Manual The propagation speed of an electrical current pulse through a conductive material is a function of the material’s impedance. Any change in propagation speed as a signal passes between different materials or impedances will result in coupling loss and reﬂections. As with the optical realm, reﬂections can result in constructive or destructive interference.
Page 287: Model 2520 Output Circuit Model
Model 2520 User’s Manual Measurement Considerations F-13 Model 2520 output circuit model Figure F-11 shows the Model 2520 pulse output circuit model. There are several unique features of this pulse circuit. The most notable is that the CURRENT OUTPUT HI termi- nal provides a path to analog ground while the CURRENT OUTPUT LO terminal sinks the current during the pulse.
Page 288: Transmission Line Model
F-14 Measurement Considerations Model 2520 User’s Manual Transmission line model Figure F-12 shows the transmission line scheme that provides the least impedance mis- match. The laser diode appears as a low-impedance path to a current pulse. By placing the laser diode in series with the source and termination of the current pulse, and by maintain- ing uniform impedance in the current path, the magnitude of reﬂections is minimized.
Page 289: Forward Voltage Measurement
Model 2520 User’s Manual Measurement Considerations F-15 Forward voltage measurement Figure F-14 shows the model of the Model 2520 voltage measurement channel. This cir- cuit has been optimized to capture the forward voltage drop across the laser diode while minimizing the impact to the laser diode under test. Figure F-15 shows the recommended cable connections for pulse sourcing and forward voltage measurement.
Page 290: Photodiode Current Measurement Channels
F-16 Measurement Considerations Model 2520 User’s Manual Photodiode current measurement channels Figure F-16 shows the circuit model for the dual photodiode current measurement chan- nels. Note that the bias circuit provides the bias voltage via the inner shield of the triax cable.
Page 291: Noise And Source Impedance
Model 2520 User’s Manual Measurement Considerations F-17 Noise and source impedance Noise can seriously affect sensitive current measurements. This section discusses how DUT (device under test) resistance and capacitance affect noise performance. DUT resistance The resistance of the DUT will affect the noise performance of the ammeters. As the DUT resistance is reduced, the noise gain of the ammeter will increase.
Page 292: Source Capacitance
F-18 Measurement Considerations Model 2520 User’s Manual Source capacitance DUT source capacitance will also affect the noise performance of the Model 2520 amme- ters. In general, as source capacitance increases, the noise gain also increases. The elements of interest for this discussion are the capacitance (C ) of the DUT and the internal feedback capacitance (C ) for the ammeter.
Page 293: Offset Currents
Model 2520 User’s Manual Measurement Considerations F-19 Offset currents Internal offset current — The ideal ammeter should read zero when its input terminals are left open. Practical ammeters, such as those in the Model 2520, do have some small current that ﬂows when the input is open. This current is known as the input offset current, and it is caused by bias currents of active devices as well as by leakage currents through insulators within the instrument.
Page 294: Voltage Burden
F-20 Measurement Considerations Model 2520 User’s Manual Voltage burden The input resistance of the ammeter causes a small voltage drop across the input terminals. This voltage is known as the voltage burden and it can cause measurement errors. Refer to Figure F-17 to see how voltage burden affects detector current measurements.
Page 295: Light
Model 2520 User’s Manual Measurement Considerations F-21 this purpose, measuring instruments should be placed on their lowest ranges. The conﬁgu- ration that results in the lowest noise signal is the one that should be used. Figure F-18 Eliminating ground loops Signal Leads Instrument 1 Instrument 2...
Page 296: Electrostatic Interference
F-22 Measurement Considerations Model 2520 User’s Manual Electrostatic interference Electrostatic interference occurs when an electrically charged object is brought near an uncharged object, thus inducing a charge on the previously uncharged object. Usually, effects of such electrostatic action are not noticeable because low impedance levels allow the induced charge to dissipate quickly.
Page 297: Electromagnetic Interference (Emi
Model 2520 User’s Manual Measurement Considerations F-23 Electromagnetic Interference (EMI) The electromagnetic interference characteristics of the Model 2520 comply with the elec- tromagnetic compatibility (EMC) requirements of the European Union as denoted by the CE mark. However, it is still possible for sensitive measurements to be affected by exter- nal sources.
Page 298: Gpib 488.1 Protocol
GPIB 488.1 Protocol...
Page 299: Introduction
GPIB 488.1 Protocol Model 2520 User’s Manual Introduction The Model 2520 supports two GPIB protocols: SCPI and 488.1. The 488.1 protocol is included to signiﬁcantly increase speed over the GPIB. When using the 488.1 protocol, throughput is enhanced up to 10 times for data sent to the Model 2520 (command messages) and up to 20 times for data returned by the Model 2520 (response messages).
Page 300: Protocol Differences
Model 2520 User’s Manual GPIB 488.1 Protocol Protocol differences The following information covers the differences between the 488.1 protocol and the SCPI protocol. Message exchange protocol (MEP) When the 488.1 protocol is selected, the MEP is disabled to speed up GPIB operation. The following guidelines/limitations must be followed when using the 488.1 protocol: •...
Page 301: Bus Hold-Off
GPIB 488.1 Protocol Model 2520 User’s Manual Bus hold-off *OPC, *OPC?, and *WAI are still functional but are not needed for the 488.1 protocol. When sending commands, the GPIB is automatically held off when it detects a terminator. The hold-off is released when all the commands have ﬁnished executing, or if there is some parser or command error.
Page 302: Example Programs
Example Programs...
Page 303: Introduction
Example Programs Model 2520 User’s Manual Introduction This section provides several complete functional listings; for example, programs through- out this manual. These programs include: • Laser diode test program from Section • Linear staircase sweep program from Section • List (custom) sweep program from Section Hardware requirements The following computer hardware is required to run the example programs:...
Page 304: Laser Diode Test Program
Model 2520 User’s Manual Example Programs Laser diode test program The program listing below performs laser diode testing as covered in Section 4. This pro- gram sets up the following operating modes: • Laser diode measurement: 10V range, power math function. •...
Page 305: Linear Staircase Sweep Program
Example Programs Model 2520 User’s Manual Linear staircase sweep program The program listing below performs a linear sweep as covered in Section 7. This program sets up the following operating modes: • Measure range: 5V • Source mode: sweep • Source current range: 500mA •...
Page 306: List Sweep Program
Model 2520 User’s Manual Example Programs List sweep program The program listing below performs a list (custom) sweep as covered in Section 7. This program sets up the following operating modes: • Source mode: list sweep • Source current range: 500mA •...
Page 307: Continuous Pulse Mode
Continuous Pulse Mode...
Page 308: Pulse Test Advantage
Continuous Pulse Mode Model 2520 User’s Manual Continuous pulse mode In addition to LIV characterization, laser diodes typically require some type of wavelength or spectrum measurement. In these cases, the 2520 can be used as a current pulse generator, driving the laser diode with a current pulse train while a spectrometer or other instrument makes measurements.
Page 309: Configuring The 2520 To Use Continuous Pulse Mode
Model 2520 User’s Manual Continuous Pulse Mode Minimum Duty Cycle PW = 500ns PD = 500ms DC% = 500 × 10 × 100 = 0.0001% 0.5000005 Conﬁguring the 2520 to use Continuous Pulse Mode Front panel Set up pulse mode and triggering: Press CONFIG key, then TRIG.
Page 310: Remote Configuration Over Gpib/Ieee-488
Continuous Pulse Mode Model 2520 User’s Manual Remote conﬁguration over GPIB/IEEE-488 Command Comment *RST Reset 2520 :SOUR1:CURR:MODE FIX Set source mode to FIXed (not sweep) :SOUR1:CURR 0.2 Set current pulse amplitude to 200mA :SOUR1:PULS:DEL 0.00033 Set pulse delay (time between pulses) to 330µs :SOUR1:PULS:WIDT 0.000001 Sets the pulse width to 1µs :TRIG:COUN CONTINUOUS...
Page 311 Index Command summary CALCulate 14-3 DISPlay 14-5 FORMat 14-6 OUTPut 14-6 Accessories SENSe 14-7 Adapters SOURce 14-9 Annunciators STATus 14-12 LSTN 10-9 SYSTem 14-13 10-9 TRACe 14-13 10-9 TRIGger 14-14 TALK 10-9 Commands Address Addressed multiline Baud rate 10-16 Common see common commands 12-1 Bench defaults Condition register...
Page 312 Configuration Laser diode Buffer 14-57 MAINFRAME 1-10 Circuit See Circuit configuration Pulse sync Detector 1-22 RS-232 Digital I/O port Signal Digital output TESTHEAD Filter 1-23, 6-5, 14-30 Triax DETECTOR GPIB Trigger link Laser diode current source VOLTAGE SENSE Laser diode measurement function Contact information Laser diode measurements 3-12...
Page 313 Display Basic reading 5-12 Factory default settings 1-15 Control 14-17 Filter 6-4, 8-4, 8-12 Example 1-13 Averaging Format 1-13 Commands Front panel tests 1-14 Configuration Math function 5-12 Configure and control 14-30 Read 14-18 Control Remote programming 1-14 Programming example Units 1-13 Remote programming...
Page 314 GPIB 488.1 Protocol GPIB commands Laser diode GPIB description Configuring measurements 3-12 Ground loops F-20 Configuring source 3-10 GTL (go to local) 10-7 Current source Current source ranges 3-2, 6-3 Front panel test procedure Front panel testing Handshake lines Impedance matching F-12 Hardware requirements Math function...
Page 315 Magnetic coupling F-10 Noise Source Magnetic fields F-22 Impedance F-17 Mainframe front panel Mainframe rear panel Math function Operating boundaries see Limit lines 5-10 Display 5-12 Operation overview Math functions Options Commands Output circuit model F-13 Conductance OUTPut subsystem 14-27 Delta Output trigger Front panel...
Page 316 Pulse phase 8-4, 8-12 Remote operation 10-1 Pulse sync output Differences to local operation 10-2 Connections Selecting an interface 10-2 Waveform Trigger model Pulse test advantage Remote programming Digital output control Display 1-14 Filter Queues 11-2, 11-19 Laser diode testing Clearing 11-4 Math functions...
Page 317 Signal handshaking 10-17 Sweep Signal-oriented measurement commands 13-1 Averaging filter during [:SENSe[1]]:DATA[:LATest]? 13-3 Configure 14-37 [:SENSe2]:DATA[:LATest]? 13-3 Configuring [:SENSe3]:DATA[:LATest]? 13-3 Custom 5-8, 7-4 FETCh? 13-2 Custom sweep commands 7-10 MEASure? 13-3 Custom waveform READ? 13-3 Data storage 5-12 Sink operation Front panel operation Software requirements Linear staircase...
Page 318 Trigger subsystem 14-57 Triggering Voltage Configuring Burden F-20 Front panel operation Voltage measurement circuit model F-15 Remote Triggers Input 8-3, 8-6, 8-11 Warranty information Output 8-13 User setups see Setups 1-14...
Page 319 Specifications are subject to change without notice. All Keithley trademarks and trade names are the property of Keithley Instruments. All other trademarks and trade names are the property of their respective companies. Keithley Instruments Corporate Headquarters • 28775 Aurora Road • Cleveland, Ohio 44139 • 440-248-0400 •...

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