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Ametek 7270 Instruction Manual

Dsp lock-in amplifier
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Model 7270
DSP Lock-in Amplifier
Instruction Manual
197852-A-MNL-E
Copyright © 2017 AMETEK ADVANCED MEASUREMENT TECHNOLOGY, INC

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  • Page 1 Model 7270 DSP Lock-in Amplifier Instruction Manual 197852-A-MNL-E Copyright © 2017 AMETEK ADVANCED MEASUREMENT TECHNOLOGY, INC...

  • Page 2: Firmware Version

    Firmware Version The instructions in this manual apply to operation of a Model 7270 DSP Lock-in Amplifier that is fitted with Version 2.20 or later operating firmware. Users of instruments that are fitted with earlier firmware versions should update them to the current version free of charge by downloading an Update Pack from our website at www.signalrecovery.com The pack includes full instructions for use.

  • Page 3: Table Of Contents

    Table of Contents Table of Contents General Safety Precautions ......................vii Chapter One, Introduction 1.1 How to Use This Manual..........................1-1 1.2 What is a Lock-in Amplifier? ........................... 1-2 1.3 Key Specifications and Benefits ........................1-3 Chapter Two, Installation and Initial Checks 2.1 Installation ................................
  • Page 4 TABLE OF CONTENTS 3.3.13 Internal Oscillator - Voltage Control .....................3-10 3.3.14 Demodulators - Dual Phase Multipliers ....................3-10 3.3.15 Demodulators - Output Filters........................3-10 3.3.16 Fast Curve Buffer ...........................3-11 3.3.17 Main Output Processor - General ......................3-11 3.3.18 Main Output Processor - Output Offset and Expand ................3-12 3.3.19 Main Output Processor - Vector Magnitude and Phase .................3-12 3.3.20 Main Output Processor - Noise Measurements ..................3-13 3.3.21 Main Output Processor - Standard Curve Buffer ...................3-14...
  • Page 5 TABLE OF CONTENTS 5.2 Menu Structure ..............................5-2 5.3 Menu Descriptions - Single Reference Mode ....................5-3 5.3.01 Main Display ............................5-3 5.3.02 Control Selection Menu .......................... 5-5 5.3.03 Main Menu 1 ............................5-7 5.3.04 Signal Channel Menu ..........................5-7 5.3.05 Reference Channel Menu ........................
  • Page 6 TABLE OF CONTENTS 5.5.12 Dual Reference and Dual Harmonic Modes DAC Menu ...............5-73 5.6 Menu Descriptions - Dual Harmonic Mode ....................5-78 5.6.01 Dual Harmonic Setup Menu ........................5-78 5.6.02 Dual Harmonic Main Display ........................5-78 5.6.03 Dual Harmonic Reference Channel Menu .....................5-82 5.6.04 Dual Harmonic Output Filters Menu 1 ....................5-84 5.6.05 Dual Harmonic Output Filters Menu 2 ....................5-85 5.6.06 Dual Harmonic Output Offset Harm 1 Menu ..................5-86...
  • Page 7 TABLE OF CONTENTS 6.7.06 Internal Oscillator ..........................6-20 6.7.07 Analog Outputs ............................6-24 6.7.08 Digital I/O .............................. 6-25 6.7.09 Auxiliary Inputs ............................. 6-26 6.7.10 Output Data Curve Buffer ........................6-26 6.7.11 Computer Interfaces ..........................6-33 6.7.12 Instrument Identification ........................6-35 6.7.13 Front Panel ............................

  • Page 8: General Safety Precautions

    TABLE OF CONTENTS GENERAL SAFETY PRECAUTIONS The equipment described in this manual has been designed in accordance with EN61010 "Safety requirements for electrical equipment for measurement, control and laboratory use", and has been supplied in a safe condition. To avoid injury to an operator or service technician the safety precautions given below, and throughout the manual, must be strictly adhered to, whenever the equipment is operated, serviced or repaired.
  • Page 9 Acknowledgment Operation of the Ethernet interface in the model 7270 relies on software code developed by the Swedish Institute of Computer Science, copyright 2001-2004, all rights reserved. In accordance with...
  • Page 10 89/336/EEC Electromagnetic Compatibility Directive, amended by 92/31/EEC & 93/68/EEC Product(s) Model 7270 DSP Lock-in Amplifier Basis on which conformity is being declared The product(s) identified above comply with the requirements of the EU directives by meeting the following standards: BS EN61326:1998 Electrical equipment for measurement control and laboratory use - EMC requirements;...

  • Page 11: Chapter One, Introduction

    Chapter 1.1 How to Use This Manual This manual gives detailed instructions for setting up and operating the SIGNAL RECOVERY Model 7270 DSP Lock-in Amplifier. It is split into the following chapters:- Chapter 1 - Introduction Provides an introduction to the manual, briefly describes the function of a lock-in amplifier and the types of measurements it may be used for, and lists the major specifications of the model 7270.

  • Page 12: What Is A Lock-In Amplifier

    DSP (digital signal processing) designs, further improving performance. The model 7270 DSP lock-in amplifier uses the latest DSP technology for signal detection, and a powerful processor for easy user operation. The low-noise analog...

  • Page 13: Key Specifications And Benefits

    Chapter 1, INTRODUCTION 1.3 Key Specifications and Benefits The SIGNAL RECOVERY Model 7270 represents a further significant advance in the application of DSP technology in the design of a lock-in amplifier. Key specifications include:  Frequency range: 0.001 Hz to 250.000 kHz ...
  • Page 14 Chapter 1, INTRODUCTION...

  • Page 15: Installation

    The shipping container should be saved for inspection by the carrier. 2.1.04 Line Cord Plug The model 7270 is fitted with a standard IEC 320 input socket on its rear panel and a suitable line cord is supplied. 2.1.05 Line Voltage Selection and Line Fuses Before plugging in the line cord, ensure that the model 7270 is set to the voltage of the AC power supply to be used.
  • Page 16 Chapter 2, INSTALLATION AND INITIAL CHECKS The line voltage setting can be seen through a small rectangular window in the line input assembly on the rear panel of the instrument (figure 2-1). If the number showing is incorrect for the local line voltage (refer to table 2-1), then the barrel selector will need to be repositioned as follows.

  • Page 17: Initial Checks

    SIGNAL RECOVERY or the nearest authorized representative for assistance. 2.2.02 Procedure 1) Ensure that the model 7270 is set to the line voltage of the power source to be used, as described in section 2.1.05. 2) With the rear-panel mounted power switch set to 0 (off), plug in the line cord to an appropriate line power source.
  • Page 18 Chapter 2, INSTALLATION AND INITIAL CHECKS Figure 2-3, Main Menu 1 6) Press one of the keys adjacent to the Auto functions menu item to enter the Auto Functions menu, shown below in figure 2-4. Figure 2-4, Auto Functions Menu 7) Press one of the keys adjacent to the Auto Default menu item.

  • Page 19: Line Frequency Filter Adjustment

    If, however, the unit is to be used in an area with a 50 Hz power line frequency the setting should be changed using the following procedure. 2.3.02 Procedure 1) Turn the model 7270 power switch to the I (on) position. 2) The instrument's front panel display will now briefly display the following:-...
  • Page 20 Chapter 2, INSTALLATION AND INITIAL CHECKS Figure 2-6, Opening Display 4) Wait until the opening display has changed to the Main Display and then press the key under the bottom right hand corner of the display identified by the legend MENU on the display once.
  • Page 21 Chapter 2, INSTALLATION AND INITIAL CHECKS Figure 2-8, Configuration Menu 1 5) Press one of the keys adjacent to the Configuration 2 menu item to enter the Configuration menu 2, shown below in figure 2-9. Figure 2-9, Configuration Menu 2 5) The present line frequency setting is shown under the LINE FREQUENCY label and is either 50 or 60 Hz.
  • Page 22 Chapter 2, INSTALLATION AND INITIAL CHECKS...

  • Page 23: Introduction

    3.2.02 Single Reference / Dual Reference Conventionally, a lock-in amplifier makes measurements such as signal magnitude, phase, etc. on the applied signal at a single reference frequency. In the model 7270 this is referred to as the single reference mode.

  • Page 24: Internal / External Reference Mode

    The model 7270 allows this multiple to be set to any value between 2 (i.e. the second harmonic) and 127, as well as unity, which is the normal mode.

  • Page 25: Signal Channel Inputs

    Chapter 3, TECHNICAL DESCRIPTION Figure 3-1, Model 7270 - Block Diagram 3.3.02 Signal Channel Inputs The signal input amplifier can be set for either single-ended or differential voltage mode operation, or single-ended current mode operation. In voltage mode a choice of AC or DC coupling is available using an FET or bipolar input device.

  • Page 26: Line Frequency Rejection Filter

    Chapter 3, TECHNICAL DESCRIPTION B (I) inputs when operating in differential input mode. It is usually given in decibels. Hence a specification of > 100 dB implies that a common mode signal (i.e. a signal simultaneously applied to both A and B (I) inputs) of 1 V will give rise to less than 10 µV of signal out of the input amplifier.
  • Page 27 Chapter 3, TECHNICAL DESCRIPTION AC Gain (dB) INPUT LIMIT (mV) 2000 1000 0.25 0.125 0.062 Table 3-1, Input Limit vs. AC Gain It is a basic property of the digital signal processing (DSP) lock-in amplifier that the best demodulator performance is obtained by presenting as large a signal as possible to the main analog-to-digital converter (ADC).

  • Page 28: Anti-Aliasing Filter

    For the benefit of users who prefer to have the AC Gain value expressed in decibels, the model 7270 displays the present value of Dynamic Reserve (DR) in this form, on the input full-scale sensitivity control, for values up to 100 dB. Above 100 dB the legend changes to “DR>100”.

  • Page 29: Main Analog-To-Digital Converter

    3.3.07 Reference Channel Inputs The 7270 provides two signal inputs for an external reference signal. The front panel REF IN is a general-purpose input, designed to accept virtually any periodic waveform with a 50:50 mark-space ratio and of suitable amplitude, while the rear- panel TTL REF IN is suitable for TTL-logic level input signals.

  • Page 30: Phase-Shifter

    Chapter 3, TECHNICAL DESCRIPTION demodulators. In single harmonic mode, the reference circuit generates the phase values of a waveform at the selected harmonic of the reference frequency. Dual harmonic mode operates in a similar way to dual reference mode, but in this case the reference circuit generates phase values for both of the selected harmonics of the reference frequency.

  • Page 31: Internal Oscillator - General

    The model 7270, in common with many other lock-in amplifiers, incorporates an internal oscillator, which may be used to drive the experiment. However, unlike many other instruments, the oscillator in the model 7270 is digitally synthesized with the result that the output frequency is extremely accurate and stable. The oscillator operates over the same frequency range as the lock-in amplifier, that is 1 mHz to 250.0 kHz.

  • Page 32: Internal Oscillator - Voltage Control

    12 dB per octave. These terms have become part of the accepted terminology relating to lock-in amplifier output filters and are used in the model 7270 to apply to the envelope of the frequency response function of the digital finite impulse response (FIR) output filters. Accordingly the front-panel control which selects the configuration of the output filters is labeled SLOPE and the options are labeled 6, 12, 18, 24 dB/octave.

  • Page 33: Fast Curve Buffer

    1 reference cycle. 3.3.16 Fast Curve Buffer The fast curve buffer is a feature common to the models 7124, 7270, and 7230 lock- in amplifiers. It allows up to 100,000 sets of eight signals to be recorded at rates of up to 1 MSa/s (1 µs per point), and supports a variety of trigger modes.

  • Page 34: Main Output Processor - Output Offset And Expand

    Chapter 3, TECHNICAL DESCRIPTION 3.3.18 Main Output Processor - Output Offset and Expand Following the output filter, an output offset facility enables ±300% full-scale offset to be applied to any or all of the X(1), Y(1), X2, Y2 output signals. The output expand facility allows a ×10 expansion, performed by simple internal digital multiplication, to be applied to the same output signals.

  • Page 35: Main Output Processor - Noise Measurements

    Chapter 3, TECHNICAL DESCRIPTION function) when the magnitude output is to be used. Note that the majority of signal recovery applications are scalar measurements, where the phase between the required signal and the reference voltage is constant apart from possible phase reversals corresponding to changes in the sign of the quantity being measured.

  • Page 36: Main Output Processor - Standard Curve Buffer

    This design has been updated and so the 7270 is fitted with four general-purpose DAC outputs, which can be driven from a variety of output signals, as well as the traditional programmable “auxiliary DAC”...

  • Page 37: Auxiliary Analog Inputs (Adcs)

    In some cases it can be useful to determine the spectral power distribution of the input signal. The model 7270 can do this, since when the Spectral Display menu is selected, the output processor performs a discrete Fourier transform on the digitized input signal and displays the resulting spectrum.
  • Page 38 Chapter 3, TECHNICAL DESCRIPTION Auto-Phase In an Auto-Phase operation the value of the signal phase is computed and an appropriate phase-shift is then introduced into the reference channel so as to bring the value of the signal phase to zero. The intended result is to null the output of the Y channel while maximizing the output of the X channel.

  • Page 39: Main Microprocessor - User Settings

    Auto-Sensitivity followed by Auto-Phase functions. Auto-Default With an instrument of the design of the model 7270, where there are many controls of which only a few are regularly adjusted, it is very easy to overlook the setting of one of them.
  • Page 40 Chapter 3, TECHNICAL DESCRIPTION 3-18...

  • Page 41: Front Panel

    4.1 Front Panel Figure 4-1, Model 7270 Front Panel Layout As shown in figure 4-1, the model 7270's front panel has four BNC connectors, a 320 × 240 pixel color LCD display panel, ten double and four single keys positioned adjacent to the screen, four cursor-movement keys and a 12-button keypad.

  • Page 42: Lcd Screen

    The model 7270 is a very sophisticated instrument with many features and consequently had the traditional approach of using one button per control been adopted the front panel would have been very large.
  • Page 43 In some cases it is useful to be able to quickly adjust a control in equal increments, for example when monitoring the effect of changing the oscillator frequency about a given value. This is easily done in the model 7270 using a control setting feature known as Active Cursor operation.
  • Page 44 Chapter 4, FRONT AND REAR PANELS Figure 4-3, Active Cursor Activation As an example of this operation, suppose that the oscillator frequency is 1000.000 Hz and it is required to change it to 1001.000 Hz. Simultaneously press both keys adjacent to the oscillator frequency display. Move the cursor, by repeated double-key presses, until it is under the digit that is to be changed, in this case the zero to the left of the decimal point.

  • Page 45: Help Key

    To exit the help system and return to normal operation press the EXIT HELP key. 4.1.06 MENU Key The model 7270 is controlled by a series of on-screen menus. When the Main Display is shown the MENU key is used to access Main Menu 1, from which other menus may be accessed.

  • Page 46: Rear Panel

    Brief descriptions of these are given in the following text. 4.2.01 Line Power Switch CAUTION: The model 7270 may be damaged if the line voltage is set for 110 V AC operation and it is turned on with 220 V AC applied to the power input connector.

  • Page 47: Lan Connector

    Chapter 4, FRONT AND REAR PANELS both Full Speed and Hi-Speed (USB 2.0) protocols. 4.2.05 LAN Connector This connector allows the instrument to be connected to a 100-BaseT or 10-BaseT network for remote control. The IP address can be set to a static value or be set to automatic, when the instrument will accept an address allocated by a DHCP server on the network, using the controls on the Ethernet Setting Menu - see section 5.

  • Page 48: Trig In Connector

    Chapter 4, FRONT AND REAR PANELS connector on the front panel. 4.2.13 TRIG IN Connector This connector accepts a TTL-compatible input and can be used for triggering data acquisition to the internal curve buffer. The input can be set to respond to positive or negative going edges.

  • Page 49: Introduction

    Chapter 5.1 Introduction This chapter describes how to operate the model 7270 using the front panel controls, and discusses its capabilities when used in this way. Chapter 6 provides similar information for when the unit is operated remotely using one of the computer interfaces.

  • Page 50: Menu Structure

    Chapter 5, FRONT PANEL OPERATION reference mode but with the input to the second set of demodulators taken as the X- channel output from the first, allows the 7270 to make this measurement in a single instrument. Dual Harmonic Dual harmonic mode allows the simultaneous measurement of two different harmonics of the input signal.

  • Page 51: Menu Descriptions - Single Reference Mode

    Chapter 5, FRONT PANEL OPERATION followed by the Signal Channel key shown in Main Menu 1; to return to Main Menu 1 press the Previous Menu key on the Signal Channel menu. Note that all menus provide a Previous Menu key allowing the user to return one step up the menu "tree".
  • Page 52 Chapter 5, FRONT PANEL OPERATION Output Description Numeric Displays only: Resultant (Magnitude) output as a percentage of full-scale sensitivity Noise output as a percentage of full-scale sensitivity ° Phase output in degrees X channel output as a percentage of full-scale sensitivity Output Description Numeric Displays only (continued):...

  • Page 53: Control Selection Menu

    Chapter 5, FRONT PANEL OPERATION adjusted from 0 dB to 90 dB in 6 dB steps, although not all settings are available at all full-scale sensitivity settings. If the automatic control is turned on, then the control cannot be adjusted, but the present value of AC Gain is still displayed. In either mode, changing the full-scale sensitivity may result in a change to the AC Gain.
  • Page 54 2.000 kHz. RELOCK EXT. REFERENCE The 7270 includes frequency-dependent calibration parameters. When operating in Internal reference mode the correct parameters can be chosen because the reference frequency is equal to the specified oscillator frequency. In External reference mode the applied frequency is measured, and the measured value is used to select the correct parameters.

  • Page 55: Main Menu 1

    Keypad or Active Cursor controls - see section 4.1.04. OSC AMPLITUDE This control sets the amplitude of the signal at the 7270’s OSC OUT connector to any value between 1 mV and 5 V rms. Adjustment is faster using the Keypad or Active Cursor controls - see section 4.1.04.
  • Page 56 Chapter 5, FRONT PANEL OPERATION Figure 5-5, Signal Channel Menu 1 - Voltage Input Mode Figure 5-6, Signal Channel Menu 1 - Current Input Mode The Signal Channel Menu 1 has four controls affecting the instrument's signal input channel, and a key for accessing Signal Channel Menu 2. Changes to the setting of these controls can be made by using the adjacent keys, with the currently active selection being shown in highlighted text.
  • Page 57 Chapter 5, FRONT PANEL OPERATION INPUT SHELL The input connector shells can optionally be floated or connected to chassis ground as follows:- GROUND The shells of the A and B (I) connectors are connected directly to chassis ground. FLOAT The shells of the A and B (I) connectors are connected to chassis ground via a 1 k...
  • Page 58 Chapter 5, FRONT PANEL OPERATION Figure 5-7, Signal Channel Menu 2 The Signal Channel Menu 2 has four controls affecting the instrument's signal input channel, and a key for accessing Signal Channel Menu 1. Changes to the setting of these controls can be made by using the adjacent keys, with the currently active selection being shown in highlighted text.

  • Page 59: Reference Channel Menu

    Chapter 5, FRONT PANEL OPERATION amplifier is necessary to achieve the best results. This control allows the user to select whether this adjustment is carried out automatically or remains under manual control. In this setting the AC Gain may be manually adjusted from the Main Display. In this setting the AC Gain value is automatically selected by the instrument, depending on the full-scale sensitivity.
  • Page 60 Chapter 5, FRONT PANEL OPERATION Figure 5-8, Reference Channel Menu The Reference Channel menu has five controls affecting the instrument's reference channel. Changes to the setting of these controls can be made by using the adjacent keys. REF SOURCE This control allows selection of the source of reference signal used to drive the reference circuitry, and has three settings:- The lock-in amplifier's reference is taken from the instrument's internal oscillator.

  • Page 61: Output Filters Menu

    Chapter 5, FRONT PANEL OPERATION AUTO PHASE In an Auto-Phase operation the value of the signal phase with respect to the reference is computed and an appropriate phase-shift is then introduced into the reference channel so as to bring the difference between them to zero. The intended result is to null the output of the Y channel while maximizing the output of the X channel.

  • Page 62: Output Offset & Expand Menu

    Chapter 5, FRONT PANEL OPERATION the Fast time constant mode) than would otherwise be the case. In this setting, the actual time constant will not change if the reference changes. Note that, depending on the reference frequency, output time constants shorter than 100 ms cannot be used.

  • Page 63: Output Equations Menu

    Chapter 5, FRONT PANEL OPERATION allow manual adjustment of the X channel and Y channel output offsets. The offset level set by the controls, which can be any value between -300% and +300% in 0.01% steps, is added to the X channel or Y channel output when the X channel or Y channel offset is switched on.
  • Page 64 Chapter 5, FRONT PANEL OPERATION Figure 5-11, Output Equations Menu The Output Equations menu is used to define more complex calculations on the instrument outputs than are possible using the basic ratio and log ratio options. There are two user-defined equations, Equation 1 and Equation 2, which take the following form:- ...

  • Page 65: Oscillator Menu

    Chapter 5, FRONT PANEL OPERATION The calculation is performed using 64-bit integers to maintain full accuracy through to the 32-bit result that is displayed immediately below the equation and is constantly updated. Care must be taken in defining the equations so as to make the best use of the available output range.

  • Page 66: Frequency Sweep Menu

    Chapter 5, FRONT PANEL OPERATION Figure 5-13, Oscillator Menu Structure Changes to the setting of the controls on the Oscillator menu can be made by using the adjacent keys. OSC FREQUENCY This control, which duplicates the Main Display OSC FREQUENCY control, allows the instrument's internal oscillator frequency to be set to any value between 0.001 Hz and 250.000 kHz with a 1 mHz resolution.
  • Page 67 Chapter 5, FRONT PANEL OPERATION Figure 5-14, Frequency Sweep Menu The Frequency Sweep menu has nine controls affecting the instrument's internal oscillator, and a link to the Curve Buffer menu (see section 5.3.24). Changes to the setting of the controls can be made by using the adjacent keys.
  • Page 68 Chapter 5, FRONT PANEL OPERATION Note that the time per step defined here also applies to oscillator amplitude sweeps - see section 5.3.11. ARMED When this control is set to YES, the frequency sweep is armed. The sweep can then be started in one of two ways: a) If the LINK TO CURVE BUFFER control is set to YES then the sweep will be started at the same time as a curve buffer acquisition starts (see section 5.3.24).

  • Page 69: Amplitude Sweep Menu

    Chapter 5, FRONT PANEL OPERATION 1000.000 Hz 1610.510 Hz 1100.000 Hz 1771.561 Hz 1210.000 Hz 1948.717 Hz 1331.000 Hz 2000.000 Hz 1464.100 Hz LINEAR Selects a linear relationship. Pressing the Curve Buffer key accesses the Curve Buffer menu, described in section 5.3.24, while pressing the Previous Menu key returns control to the Oscillator Menu.
  • Page 70 Chapter 5, FRONT PANEL OPERATION STOP AMPLITUDE This control defines the stop amplitude for the amplitude sweep, which may be set to any value between 0.000 V rms and 5.000V rms with a 1 µV resolution. Adjustment is faster using the Keypad or Active Cursor controls - see section 4.1.04. STEP AMPLITUDE This control defines the amount by which the oscillator amplitude is changed at each step.

  • Page 71: Amplitude Modulation Menu

    Chapter 5, FRONT PANEL OPERATION CONTINUE Pressing the adjacent key restarts the paused amplitude sweep from the present amplitude. The control changes to PAUSE Note that if the oscillator frequency sweep (see section 5.3.10) is also armed then the controls that start, pause, continue and stop on the Amplitude Sweep menu will also control the frequency sweep.

  • Page 72: Frequency Modulation (Vco) Menu

    Chapter 5, FRONT PANEL OPERATION VOLTAGE SPAN This control sets the range of input voltages that will be translated into the set range of modulation. FILTER CONTROL The amplitude modulation control signal can be filtered by a simple digital low-pass FIR filter before being applied to the oscillator, which can be useful for eliminating noise or glitches on the modulating signal.

  • Page 73: Auto Functions Menu

    Chapter 5, FRONT PANEL OPERATION When the VCO is enabled, the internal oscillator’s output frequency can be modulated by a signal applied to the ADC1 auxiliary input. The controls operate as follows:- CENTER FREQUENCY This control may be set to any value between 0.001 Hz and 250.00 kHz. Adjustment is faster using the Keypad or Active Cursor controls - see section 4.1.04.
  • Page 74 Chapter 5, FRONT PANEL OPERATION Figure 5-18, Auto Functions Menu This menu has five controls for activating the auto functions built into the instrument. Note that once these functions complete, the Auto Functions menu is replaced by the Main Display. The functions operate as follows:- AUTO SENSITIVITY This function only operates when the reference frequency is above 1 Hz.
  • Page 75 Chapter 5, FRONT PANEL OPERATION 2) Execute an Auto-Offset operation, which will reduce the X channel and Y channel outputs to zero. 3) Re-establish the source of input signal. The X channel and Y channel outputs will now indicate the true level of input signal, at the present reference phase setting.

  • Page 76: Configuration Menu 1

    Chapter 5, FRONT PANEL OPERATION AUTO DEFAULT With an instrument of the design of the model 7270, where there are many controls of which only a few are regularly adjusted, it is very easy to overlook the setting of one of them. Consequently an Auto-Default function is provided, which sets all the controls to a defined state.
  • Page 77 Chapter 5, FRONT PANEL OPERATION Figure 5-20, Configuration Menu Structure The controls on the Configuration menu operate as follows. NOISE MEASUREMENT This control is used to configure the instrument for noise measurements. When turned ON, the Main Display output displays (see section 5.3.01) are set as follows: Display Position Displayed Output Noise expressed in V/Hz in large digits...

  • Page 78: Communications Menu

    Chapter 5, FRONT PANEL OPERATION instrument's operating firmware. The firmware in the instrument can be updated to the latest version by connecting it to a PC via the RS232 or USB interfaces and running an Update program. Options This key gives access to the Options Menu, which is used to install firmware options within the instrument.
  • Page 79 ECHO This control, when switched on, causes the model 7270 to echo each character received over the RS232 interface back to the controlling computer. The computer should wait until the echoed character is returned before it sends the next character.

  • Page 80: Ethernet Settings Menu

    PROMPT This control has two settings, as follows:- A prompt character is generated by the model 7270 after each command response to indicate that the instrument is ready for a new command. The prompt character is either a "*" or a "?" If a "?" is generated, it indicates that an overload, reference unlock, parameter error or command error has occurred.
  • Page 81 Chapter 5, FRONT PANEL OPERATION the Ethernet computer interface, as follows:- IP Address Assignment This control has two settings, as follows:- MANUAL When set to manual, the IP address of the instrument is set manually, using the IP Address control on this menu. AUTOMATIC In automatic mode, if the instrument is connected to a network with a DHCP server then it will adopt the address given to it be the server.

  • Page 82: Usb Status Menu

    Chapter 5, FRONT PANEL OPERATION Link Status This indicator shows whether the instrument is connected to a working network. Crossover Status This indicator shows whether the cable connecting the instrument to the network is straight-through or crossover. Speed This indicator shows the network speed. Duplex This indicator shows whether the network is using half or full duplex transmission to and from the instrument.

  • Page 83: Communications Monitor

    Chapter 5, FRONT PANEL OPERATION STATUS This indicates whether the instrument is connected to the USB and has been correctly enumerated by the controlling computer. CONNECTION SPEED If the USB status is connected, then this indicator shows the actual connection speed. OUTPUT TERMINATOR This has two settings, as follows: NULL...

  • Page 84: Options Menu

    Chapter 5, FRONT PANEL OPERATION CLEAR SCREEN The input and output displays scroll once they are full so that they always display the most recent characters received and sent. Pressing the Clear Screen key clears both areas. Pressing the Previous Menu key returns control to either the Communications menu or the USB Status menu, or the RS232 Setting menu, depending on how the Communications Monitor display was accessed.

  • Page 85: Spectral Display

    Positive operation is the same as earlier SIGNAL RECOVERY lock-in amplifiers, such as the models 7220, 7225, 7265, 7265, 7280, 5209 and 5210. When set to Negative it is the same as earlier versions of firmware in the models 7270, 7124 and 7230.
  • Page 86 2 kHz, the nominal range is 0 kHz to 458.0 kHz, although frequencies above 250 kHz are not usually of interest since they lie outside the frequency range of signals that the 7270 can measure. With the finest resolution of 0.2 kHz, the display range is nominally 45.8 kHz.

  • Page 87: Main Menu 2

    Main Menu 2, which is shown in figure 5-30. Figure 5-30, Main Menu 2 Main Menu 2 has keys used to access the extended features found in the model 7270, via a series of sub-menus. The relationship of these sub-menus to Main Menu 2 is shown in figure 5-31.

  • Page 88: Curve Buffer Menu

    Chapter 5, FRONT PANEL OPERATION Figure 5-31, Main Menu 2 Menu Structure The Communications menu has already been described in section 5.3.16, but the other sub menus are described in the following sections. Pressing the Previous Menu key returns control to Main Menu 1. 5.3.25 Curve Buffer Menu When Main Menu 2 is displayed, pressing the Curve buffer key accesses the Curve Buffer menu, which is shown in figure 5-32.
  • Page 89 FPGA memory, with the fastest time per point being reduced to 1 µs. Fast mode is a new mode in the model 7270 but in some ways can be considered as an extension to the Transient Recorder mode found in earlier SIGNAL RECOVERY DSP lock-in amplifiers.

  • Page 90: Curve Trigger Menu

    Chapter 5, FRONT PANEL OPERATION TRIG IN connector on the rear panel of the instrument. CURVE BUFFER FULL Acquisition stops as soon as the number of points acquired equals the Curve Length as set on the Curve Buffer menu. INTERNAL Acquisition stops directly when the Stop Sweep key is pressed.
  • Page 91 Chapter 5, FRONT PANEL OPERATION ACQUISITION TRIGGER The acquisition trigger is a "per curve" (start) or "per point" (sample) trigger detecting the signal at the TRIG IN connector on the rear panel of the instrument, as follows: INTERNAL The curve buffer acquisition is not affected by input triggers PER CURVE Acquisition starts on detection of a rising edge on the TTL trigger signal.

  • Page 92: Curve Select Menu

    Chapter 5, FRONT PANEL OPERATION SAMPLE A trigger output is generated each time that a point is acquired into the buffer. TRIG OUT POLARITY This control has two settings:- RISING The trigger output is marked by the rising edge of the signal. FALLING The trigger output is marked by the falling edge of the signal.

  • Page 93: Single Graph Menu

    Chapter 5, FRONT PANEL OPERATION stored when data acquisition to the curve buffer is initiated. The possible data types (outputs) that can be stored to the curve buffer are shown on the upper part of the screen. Controls allow between one and all of these data types to be selected for storage, with those that are selected being indicated by being shown in highlighted text.

  • Page 94: Double Graph Menu

    Chapter 5, FRONT PANEL OPERATION SCALE keys The top and bottom left-hand keys are used to adjust the upper and lower limits of the vertical axis with a 1% resolution, the set maximum and minimum values being shown adjacent to them. AUTO SCALE keys The upper and lower middle pairs of left-hand keys (or the...
  • Page 95 Chapter 5, FRONT PANEL OPERATION Figure 5-37, Double Graph Menu The double graph display is similar to that of the single graph, but displays two curves. If there is no data in the curve buffer then the graph will show two horizontal straight lines representing zero.

  • Page 96: User Settings Menu

    Chapter 5, FRONT PANEL OPERATION CURSOR keys As with the single graph mode, the bottom right-hand keys and the cursor-movement keys control the position of the cursor. The current point number is displayed in the bottom right-hand corner of the display and the value of the curves at their intersection with the cursor appear above the relevant Curve 1 and Curve 2 data types.

  • Page 97: Adc Menu

    Chapter 5, FRONT PANEL OPERATION settings are to be restored. A message will be displayed while the settings are restored. Deleting an Instrument Setting Press the Delete memory key, which will cause the Memory keys or those memories containing settings information to appear. Press either side of the key next to the Memory number at which the settings are to be deleted.

  • Page 98: Dac Menu

    Chapter 5, FRONT PANEL OPERATION BURST ADC1 The burst modes are for use in conjunction with the curve buffer operating in the Fast mode. When Burst ADC1 is selected, a burst of conversions at the rates set by the curve buffer TIME PER POINT control is performed on ADC1 only. The results are stored to the curve buffer, with the number of conversions being set by the curve length control on the Curve Buffer menu - see section 5.3.24.
  • Page 99 Chapter 5, FRONT PANEL OPERATION hand side of the screen is set to USER DAC. DAC1 SETUP, DAC2 SETUP, DAC3 SETUP, and DAC4 SETUP These four controls select which signal will be made available at the corresponding DAC 1 to DAC 4 connectors on the rear panel of the instrument. The following settings are available, but note that internal connection limitations mean that not all settings are available for each DAC connector.
  • Page 100 Chapter 5, FRONT PANEL OPERATION N%fs DAC Voltage +300 7.5 V +100 2.5 V 0.0 V NOTE: When NOISE is selected as an output, the noise measurement mode (Configuration Menu) must be ON. If it is not, a warning message is displayed which offers the option of turning it on or deselecting NOISE as an analog output.
  • Page 101 Chapter 5, FRONT PANEL OPERATION setting, the X1 channel output were maximized and a 1 V signal were applied to the ADC1 input, then the value of LOG RATIO would be:-         LOG RATIO log 1.000 ...

  • Page 102: Digital Port Menu

    Chapter 5, FRONT PANEL OPERATION EXT ADC1 MON When set to the EXT ADC1 MON setting the corresponding DAC connector on the rear panel of the instrument outputs a voltage representing the voltage at the rear-panel ADC1 input connector. SYNC OSC When set to the SYNC OSC setting the corresponding DAC connector on the rear panel of the instrument outputs a voltage representing the sinusoidal waveform applied to the first in-phase demodulator.

  • Page 103: Menu Descriptions - Virtual Reference Mode

    Chapter 5, FRONT PANEL OPERATION can be set to any number between 0 (all bits at logic "0") and 255 (all bits at logic "1"). DECIMAL INPUT This displays the current logic state of all eight bits, regardless of whether they are inputs or outputs.
  • Page 104 Chapter 5, FRONT PANEL OPERATION Figure 5-43, Virtual Reference Menu This menu has six controls affecting the virtual reference mode, a single display, and two keys to establish virtual lock. The left-hand side of the display is used for the semi-automatic method of establishing Virtual Reference mode, with the right-hand side being used for the manual mode.
  • Page 105 Chapter 5, FRONT PANEL OPERATION figure 5-45. Manual Setup If the semi-automatic setup method does not work because the signal requires a time constant longer than 100 ms then the initial search can be performed manually. This can be done using the controls on the right-hand side of the display, and the Start Frequency control on the left-hand side.

  • Page 106: Virtual Reference Main Display

    Chapter 5, FRONT PANEL OPERATION 5.4.02 Virtual Reference Main Display Figure 5-44, Main Display - Virtual Reference Mode In virtual reference mode, the instrument operates exactly as in single reference mode, with the following exceptions:- The Main Display always shows the annotation "Virtual Reference Mode" in the bottom right-hand section of the display as a warning to the user that this mode is being used.

  • Page 107: Virtual Reference Configuration Menu

    5.5 Menu Descriptions - Dual Reference Mode 5.5.01 Dual Reference Setup Menu The dual reference mode allows the model 7270 to simultaneously measure signals applied to the signal input at two different reference frequencies. The source of these reference signals is any two from the three available options of Internal, External Front Panel, and External Rear Panel.

  • Page 108: Dual Reference Main Display

    Chapter 5, FRONT PANEL OPERATION Figure 5-45, Dual reference Setup Menu 5.5.02 Dual Reference Main Display Once dual reference has been activated, the Main Display - Dual reference Mode is displayed, as shown in figure 5-46. Figure 5-46, Main Display - Dual Reference Mode In dual reference mode, controls and displays relating to the reference channel 1 signal carry the suffix "1"...
  • Page 109 1 channel operates, in the range 1 st (fundamental mode) to 127 th. RELOCK EXT. REFERENCE The 7270 includes frequency-dependent calibration parameters. In Dual reference mode the correct parameters can be chosen for the internal reference channel because 5-61...
  • Page 110 OSC AMPLITUDE This control sets the amplitude of the signal at the 7270’s instrument OSC OUT connector to any value between 1 µV and 5 V rms. Adjustment is faster using the Keypad or Active Cursor controls - see section 4.1.04.
  • Page 111 Chapter 5, FRONT PANEL OPERATION Output Description Title Numeric Displays only: Resultant (Magnitude) output, reference 1, %FS Resultant (Magnitude) output, reference 2, %FS Noise output about reference 1, % FS Noise output about reference 2, % FS  ° Phase output, reference 1, in degrees ...

  • Page 112: Dual Reference Channel Menu 1

    Chapter 5, FRONT PANEL OPERATION 5.5.03 Dual Reference Channel Menu 1 In dual reference mode, the reference channel is controlled by the Dual Reference Channel menus, which differ from the Reference Channel menu used in the other four modes. In addition, controls are needed for the corresponding output channels, and so the Output Filters and Output Offset sub-menus also change.
  • Page 113 Chapter 5, FRONT PANEL OPERATION Figure 5-48, Dual Reference Channel Menu 1 The Dual Reference Channel Menu 1 has four controls affecting the instrument's reference channel, and a key to access Dual Reference Channel Menu 2. Changes to the setting of these controls can be made by using the adjacent keys.

  • Page 114: Dual Reference Channel Menu 2

    Chapter 5, FRONT PANEL OPERATION 5.5.04 Dual Reference Channel Menu 2 Figure 5-49, Dual Reference Channel Menu 2 The Dual Reference Channel Menu 2, shown above in figure 5-49, has four controls affecting the instrument's reference channel, and a key to access Dual Reference Channel Menu 1.
  • Page 115 Chapter 5, FRONT PANEL OPERATION Figure 5-50, Dual Reference Output Filters Menu 1 The Dual Reference Output Filters Menu 1 has four controls affecting the instrument's output low-pass filters, and a key to access the Output Filters Menu 2. Changes to the setting of these controls can be made by using the adjacent keys.

  • Page 116: Dual Reference Output Filters Menu 2

    Chapter 5, FRONT PANEL OPERATION NORMAL In this setting, the analog outputs are derived from the output processor. The update rate is always 1 kHz, the output filter time constant can be set to values between 5 ms and 100 ks in a 1-2-5 sequence, and all four output filter slope settings are available.

  • Page 117: Dual Reference Output Offset Ref 1 Menu

    Chapter 5, FRONT PANEL OPERATION pressing the Previous Menu key returns control to Main Menu 1. 5.5.07 Dual Reference Output Offset Ref 1 Menu In dual reference mode, when Main Menu 1 is displayed, pressing a key adjacent to the Output Offset item accesses the Output Offset Ref 1 menu, which is shown in figure 5-52.

  • Page 118: Dual Reference Output Offset Ref 2 Menu

    Chapter 5, FRONT PANEL OPERATION X&Y Both X1 channel and Y1 channel output offsets are switched on. AUTO OFFSET1 This control adjusts the X1 offset and Y1 offset values so that the X1 channel and Y1 channel outputs are zero. Any small residual values can normally be removed by calling Auto-Offset for a second time after a suitable delay to allow the outputs to settle.

  • Page 119: Dual Reference Auto Functions Menus

    Chapter 5, FRONT PANEL OPERATION NONE Both X2 channel and Y2 channel output offsets are switched off. The X2 channel output offset is switched on. The Y2 channel output offset is switched on. X&Y Both X2 channel and Y2 channel output offsets are switched on. AUTO OFFSET2 This control adjusts the X2 offset and Y2 offset values so that the X2 channel and Y2 channel outputs are zero.

  • Page 120: Dual Reference Configuration Menu

    Chapter 5, FRONT PANEL OPERATION 5.5.10 Dual Reference Configuration Menu Figure 5-55, Configuration Menu - Dual reference Mode In dual reference mode, the Configuration menu appears as above. To leave dual reference mode and return to single reference mode press the Single Reference key, to switch to dual harmonic mode, press the Dual Harmonic key.

  • Page 121: Dual Reference And Dual Harmonic Modes Dac Menu

    Chapter 5, FRONT PANEL OPERATION Figure 5-57, Curve Select Menu - Fast Mode For the standard mode, this menu is used to select the instrument outputs that will be stored when data acquisition to the curve buffer is initiated. The possible data types (outputs) that can be stored to the curve buffer are shown on the upper part of the screen.
  • Page 122 Chapter 5, FRONT PANEL OPERATION Figure 5-58, DAC Menu - Dual Reference and Dual Harmonic Modes The DAC menu is used to configure the signal that will appear on the four DAC connectors on the rear panel of the instrument. On the left hand side of the panel four controls are used to set the DC voltages of the auxiliary DAC outputs, while on the right hand side four controls are used to select the signal that will actually be applied to the DAC 1 to DAC 4 connectors.
  • Page 123 Chapter 5, FRONT PANEL OPERATION DAC Voltage +300 7.5 V +100 2.5 V 0.0 V -100 -2.5 V -300 -7.5 V MAG1% (2.5V fs) When set to MAG1% the corresponding DAC connector on the rear panel of the instrument outputs a voltage related to the MAG1%fs or R % front panel displays as follows:- MAG1%fs...
  • Page 124 Chapter 5, FRONT PANEL OPERATION MAG2%fs DAC Voltage +300 7.5 V +100 2.5 V 0.0 V PHASE2 (+9 V = +180°) When in this setting the corresponding DAC connector on the rear panel of the instrument outputs a voltage related to the PHA2 or  front panel displays as follows:- PHA2 or ...
  • Page 125 Chapter 5, FRONT PANEL OPERATION RATIO1 DAC Voltage +7.5 7.5 V +2.5 2.5 V 0.0 V -2.5 -2.5 V -7.5 -7.5 V LOG RATIO1 When set to LOG RATIO1 the corresponding DAC connector on the rear panel of the instrument outputs a voltage related to the LOG RATIO calculation, which is defined as follows:- ...

  • Page 126: Menu Descriptions - Dual Harmonic Mode

    5.6 Menu Descriptions - Dual Harmonic Mode 5.6.01 Dual Harmonic Setup Menu The dual harmonic mode allows the model 7270 to simultaneously measure signals applied to the signal input at two different harmonics of the reference frequency. The reference may be either externally supplied or derived from the internal oscillator.
  • Page 127 Chapter 5, FRONT PANEL OPERATION Figure 5-60, Main Display - Dual Harmonic Mode In dual harmonic mode, controls and displays relating to the first detection harmonic carry the suffix "1" and those for the second, the suffix "2". Hence, for example, if a reference frequency of 1 kHz is applied, Harmonic 1 is set to 3 and Harmonic 2 to 5, the instrument will measure signals at both 3 kHz and 5 kHz.
  • Page 128 3 kHz and 5 kHz. RELOCK EXT. REFERENCE The 7270 includes frequency-dependent calibration parameters. When operating in Internal reference mode the correct parameters can be chosen because the reference frequency is equal to the specified oscillator frequency. In External reference mode the applied frequency is measured, and the measured value is used to select the correct parameters.
  • Page 129 Keypad or Active Cursor controls - see section 4.1.04. OSC AMPLITUDE This control sets the amplitude of the signal at the 7270’s instrument OSC OUT connector to any value between 1 µV and 5 V rms. Adjustment is faster using the Keypad or Active Cursor controls - see section 4.1.04.

  • Page 130: Dual Harmonic Reference Channel Menu

    Chapter 5, FRONT PANEL OPERATION Equations menu (see section 5.3.08), allow the selection of the additional outputs as variables. For example, it is possible to calculate a value proportional to the ratio of the X channel output to that of the X channel output.
  • Page 131 Chapter 5, FRONT PANEL OPERATION Figure 5-62, Dual Harmonic Reference Menu The Dual Harmonic Reference menu has five controls affecting the instrument's reference channel. Changes to the setting of these controls can be made by using the adjacent keys. REF SOURCE This control allows selection of the source of reference signal used to drive the reference circuitry, and has three settings:- The lock-in amplifier's reference is taken from the instrument's internal...

  • Page 132: Dual Harmonic Output Filters Menu 1

    Chapter 5, FRONT PANEL OPERATION 5.6.04 Dual Harmonic Output Filters Menu 1 In dual harmonic mode, pressing the Output Filters key on Main Menu 1 accesses the Dual Harmonic Output Filters Menu, shown in figure 5-63. Figure 5-63, Dual Harmonic Output Filters Menu 1 The Dual Harmonic Output Filters Menu 1 has four controls affecting the instrument's output low-pass filters, and a key to access Output Filters Menu 2.

  • Page 133: Dual Harmonic Output Filters Menu 2

    Chapter 5, FRONT PANEL OPERATION AUTO This is the same as the ON setting except that if the reference changes the time constant will be recalculate to the nearest legal synchronous setting. TIME CONSTANT MODE This control has two settings, as follows:- NORMAL In this setting, the analog outputs are derived from the output processor.

  • Page 134: Dual Harmonic Output Offset Harm 1 Menu

    Chapter 5, FRONT PANEL OPERATION SLOPE 2 The roll-off of the outputs filters can be set, using this control, to either 6 dB or 12 dB per octave (Fast time constant mode) or 6 dB, 12 dB, 18 dB or 24 dB per octave (Normal time constant mode).

  • Page 135: Dual Harmonic Output Offset Harm 2 Menu

    Chapter 5, FRONT PANEL OPERATION The X1 channel output offset is switched on. The Y1 channel output offset is switched on. X1&Y1 Both X1 channel and Y1 channel output offsets are switched on. AUTO OFFSET1 This control adjusts the X1 offset and Y1 offset values so that the X1 channel and Y1 channel outputs are zero.

  • Page 136: Dual Harmonic Auto Functions Menus

    Chapter 5, FRONT PANEL OPERATION on both X2 channel and Y2 channel output offsets. OFFSET STATUS This control allows the X2 channel and Y2 channel output offsets, set by the above level controls, to be switched on to either or both outputs, or to be switched off. It therefore has four settings, as follows:- Both X2 channel and Y2 channel output offsets are switched off.

  • Page 137: Dual Harmonic Configuration Menu

    This completes the description of the dual harmonic mode menus. 5.7 Typical Lock-in Amplifier Experiment The model 7270 is a complex instrument that has many controls and the following basic checklist may be helpful in setting up the instrument for manual operation in single reference mode.
  • Page 138 Chapter 5, FRONT PANEL OPERATION If using external reference mode, use the Reference Channel menu to select one of the four external inputs, and connect the reference signal to the correct connector. Auto-Measure Use the Auto-Measure function on the Auto Functions menu to set the instrument so that it is correctly displaying the signal.

  • Page 139: Introduction

    Chapter 6.1 Introduction The model 7270 includes RS232, USB and Ethernet interface ports, designed to allow it to be completely controlled from a remote computer. Virtually all of the instrument's controls may be operated, and all of the outputs can be read, via these interfaces.

  • Page 140: General Features

    In the model 7270 the baud rate can be set to a range of different values up to 38,400, corresponding to a minimum time of less than 0.25 ms for a single character.

  • Page 141: Choice Of Number Of Data Bits

    Therefore no software is provided in the model 7270 for dealing with parity errors. Where long cables are in use, it may be advisable to make use of a lower baud rate. The result is that any of the parity check options may be used, but the no-parity option will result in slightly faster communication.

  • Page 142: Terminators

    Chapter 6, COMPUTER OPERATION changed by the use of a software switch, the RS232 null modem cable that is used must connect TD on each side through to RD on the other side, and assert CTS, DSR, and DCD on each side when RTS and DTR are asserted on the opposite side, in addition to connecting the transmit data, receive data, and logic ground signals.

  • Page 143: Usb Operation

    Chapter 6, COMPUTER OPERATION response is finished and the instrument is ready for a new command. The prompt takes one of two forms. If the command contained an error, either in syntax or by a command parameter being out of range, or alternatively if an overload or reference unlock is currently being detected, the prompt is a question mark character ? (ASCII 63).

  • Page 144: General Features

    Chapter 6, COMPUTER OPERATION Readers should refer to the document “USB Drivers for the Model 7124 and 7270 Lock-in Amplifiers”, available from the www.signalrecovery.com website, for further information about installing these drivers. 6.4.02 General Features Unlike the RS232 interface, there is no difficulty ensuring that the correct cable type is used for USB operation.

  • Page 145: Ethernet Operation

    Chapter 6, COMPUTER OPERATION text) followed by a response terminator. Where the response of the lock-in amplifier consists of two numbers in succession, they are separated by a byte called a delimiter. This delimiter can be any printing ASCII character and is common to all interfaces;...

  • Page 146: Sockets

    Chapter 6, COMPUTER OPERATION Clicking on the link in the left hand column accesses a “static interface” page that allows commands to be typed and the responses displayed. Figure 6-1, Built-in Home Page 6.5.03 Sockets The instrument normally accepts commands sent to socket 50000 or socket 50001 on its IP address.

  • Page 147: Delimiters

    Chapter 6, COMPUTER OPERATION In the case of commands sent to socket 50000 then three bytes are returned, in the following order: 1) A null character (ASCII 0) 2) A byte representing the value of the Status Byte (table 6-1) 3) A byte representing the value of the Overload Byte (table 6-1) In the case of commands sent to socket 50001 then one byte is returned, as follows: 1) A carriage return character (CR - ASCII 13)

  • Page 148: Command Descriptions

    Chapter 6, COMPUTER OPERATION if present may optionally be followed by n . Upper-case and lower-case characters are equivalent. Terminator bytes are defined in section 6.3.09. Where the command syntax includes optional parameters and the command is sent without the optional parameters, the response consists of a transmission of the present values of the parameter(s).
  • Page 149 Chapter 6, COMPUTER OPERATION Note that the IMODE command takes precedence over the VMODE command. DEMOD2SRC [n] Second stage demodulator signal source In the dual reference mode, the value of n sets the source of the signal for the second stage demodulators according to the following table: Signal source Main signal channel ADC (i.e.
  • Page 150 Chapter 6, COMPUTER OPERATION full-scale sensitivity IMODE=0 IMODE=1 IMODE=2 500 µV 500 pA 5 pA 1 mV 1 nA 10 pA 2 mV 2 nA 20 pA 5 mV 5 nA 50 pA 10 mV 10 nA 100 pA 20 mV 20 nA 200 pA 50 mV...

  • Page 151: Reference Channel

    Chapter 6, COMPUTER OPERATION Selection Enable 50 or 60 Hz notch filter Enable 100 or 120 Hz notch filter Enable both filters Notch Filter Center Frequencies 60 Hz (and/or 120 Hz) 50 Hz (and/or 100 Hz) 6.7.02 Reference Channel REFMODE [n] Reference mode selector The value of n sets the reference mode of the instrument according to the following table:...
  • Page 152 Chapter 6, COMPUTER OPERATION IE2 [n] Reference channel 2 source control, Dual Reference In Dual Reference mode, the value of n sets the reference channel 2 source according to the following table: Selection INT (internal) EXT (external rear panel TTLREF IN input) EXT (external front panel analog REF input) This command is only valid in Dual Reference mode REFN [n]...

  • Page 153: Signal Channel Output Filters

    Chapter 6, COMPUTER OPERATION LOCK System lock control Updates all frequency-dependent gain and phase correction parameters. VRLOCK [n] Virtual reference mode lock The Seek option of the frequency sweep mode must be used before issuing this command, for which the value of n has the following significance: Mode Disables virtual reference mode Enters virtual reference mode by enabling tracking of the signal frequency...
  • Page 154 Chapter 6, COMPUTER OPERATION TC [n] Filter time constant control The value of n sets the output filter time constant in accordance with the following table: NOISEMODE NOISEMODE NOISEMODE NOISEMODE = time constant time constant time constant time constant 10 µs 20 µs 50 µs 10 s...

  • Page 155: Signal Channel Output Amplifiers

    Chapter 6, COMPUTER OPERATION When: a) The fast output filter mode is turned on, or b) Noise measurement mode is turned ON (NOISEMODE 1) the selection is according to the following table: Slope 6 dB/octave 12 dB/octave 6.7.04 Signal Channel Output Amplifiers XOF [n X channel output offset control Selection...

  • Page 156: Instrument Outputs

    Function Operation is the same as earlier SIGNAL RECOVERY lock-in amplifiers, such as the models 7220, 7225, 7265, 7265, 7280, 5209 and 5210. Operation is the same as earlier versions of firmware in the models 7270, 7124 and 7230 MP[.] Magnitude, phase Equivalent to the compound command MAG[.];PHA[.]...
  • Page 157 Chapter 6, COMPUTER OPERATION LR[.] Log Ratio output In integer mode, the LR command reports a number equivalent to 1000×log(X/ADC1) where X is the value that would be returned by the X command and ADC1 is the value that would be returned by the ADC1 command. The response range is -3000 to +2079 In floating point mode, the LR.

  • Page 158: Internal Oscillator

    Chapter 6, COMPUTER OPERATION Variable Range ADC1 ±10000 ADC2 ±10000 ADC3 ±10000 ADC4 ±10000 0 to 100000 0 to 100000 10 0 zero 11 1 unity 12 FRQ 0 to 250000000 (i.e. reference frequency in mHz)* 13 OSC 0 to 250000000 (i.e. oscillator frequency in mHz)* Dual modes only:- 14 X2 ±30000...
  • Page 159 Chapter 6, COMPUTER OPERATION SYNCOSC [n] Synchronous Oscillator control When external reference mode is active, the parameter n sets the synchronous oscillator output in accordance with the following table: Function The oscillator is independent of the external reference frequency The oscillator is a sine wave at the same frequency as the applied reference signal but subject to any phase shift set by the phase control.
  • Page 160 Chapter 6, COMPUTER OPERATION In floating point mode n is in percent. The range of n is 0 to 100.000% Linear sweep n In fixed point mode, n is the step size in millihertz. In floating point mode n is in hertz. The range of n is 0 to 250 kHz Linear seek sweep n In fixed point mode, n...
  • Page 161 Chapter 6, COMPUTER OPERATION MENABLE [n] Oscillator amplitude/frequency modulation enable command The value of n enables the oscillator amplitude modulation function in accordance with the following table: Function Oscillator amplitude/frequency modulation disabled Oscillator amplitude modulation enabled Oscillator frequency modulation enabled AMCENTERV[.] [n] Oscillator amplitude modulation center voltage command The value of n sets the oscillator amplitude modulation center voltage;...

  • Page 162: Analog Outputs

    Chapter 6, COMPUTER OPERATION FMFILTER [n] Oscillator frequency modulation filter control command The value of n sets the oscillator frequency modulation voltage low-pass filter control in the range 0 to 10. The value of 0 gives the widest bandwidth for this filter, with the value of 10 the lowest.

  • Page 163: Digital I/O

    Chapter 6, COMPUTER OPERATION Signal (DAC2) Equation 2 User DAC2 Ext ADC1 monitor Phase2 : +9 V = +180°, -9 V = -180° (dual mode only) Signal (DAC3) Magnitude % (2.5 V FS) Noise % (2.5 V FS) Ratio: (10 × X%/ADC 1) (10 ...

  • Page 164: Auxiliary Inputs

    Chapter 6, COMPUTER OPERATION status All lines configured as inputs D0 = output, D1 - D7 = inputs D1 = output, D0 and D2 - D7 = inputs D2 = output, D0 - D1 and D3 - D7 = inputs D3 = output, D0 - D2 and D4 - D7 = inputs D4 = output, D0 - D3 and D5 - D7 = inputs D5 = output, D0 - D4 and D6 - D7 = inputs...
  • Page 165 Chapter 6, COMPUTER OPERATION CBD [n] Curve buffer define for Standard Mode Buffer Defines which data outputs are stored in the standard curve buffer when subsequent TD (take data), TDT (take data triggered) or TDC (take data continuously) commands are issued. Up to 17 (or 22 in dual reference and dual harmonic modes) curves, or outputs, may be acquired, as specified by the CBD parameter.
  • Page 166 Chapter 6, COMPUTER OPERATION the acquired curves to the computer in floating point mode. Without this information, the unit would not be able to determine the correct calibration to apply. Note that the CBD command directly determines the allowable parameters for the DC, DCB and DCT commands.
  • Page 167 Chapter 6, COMPUTER OPERATION Start condition Sample condition Stop condition Ext rising edge Points = LEN On command Ext rising edge Points = LEN Ext falling edge Points = LEN On command Ext falling edge Points = LEN Start condition Sample condition Stop condition Ext rising edge...
  • Page 168 Chapter 6, COMPUTER OPERATION this variable to any value between 0 and 32767. Halt curve acquisition Halts curve acquisition in progress. It is effective during both single (data acquisition initiated by TD command) and continuous (data acquisition initiated by TDC command) curve acquisitions.
  • Page 169 Chapter 6, COMPUTER OPERATION One curve at a time is transferred. The value of n is the bit number of the required curve, which must have been stored by the most recent CBD command. Hence n can range from 0 to 16, or 0 to 21 if a dual mode is active. If for example CBD 5 had been sent, equivalent to asserting bits 0 and 2, then the X and Magnitude outputs would be stored.
  • Page 170 Chapter 6, COMPUTER OPERATION and 2, so that DCB 0 would transfer the X channel output curve and DCB 2 the Magnitude curve. Curves 15 and 16 store the reference frequency in millihertz. When using the DCB command (although not with the other curve transfer commands), both curves need to be transferred separately.

  • Page 171: Computer Interfaces

    Chapter 6, COMPUTER OPERATION transferred. The bit corresponding to each curve is shown in the table below: Bit Decimal value Output and range X Output (±10000 FS) Y Output (±10000 FS) Magnitude Output (0 to +10000 FS) Phase (±18000 = ±180°) Sensitivity setting (1 to 27) + IMODE (0, 1, 2, 3 = 0, 32, 64, 128) Noise (0 to +10000 FS)
  • Page 172 Byte (table 6-1) \N n Address command When the model 7270 is daisy-chained with other compatible instruments this command will change which instrument is addressed. All daisy-chained instruments receive commands but only the currently addressed instrument will implement or respond to the commands. The exception is the \N n command. If n matches the address set from the front panel the instrument will switch into addressed mode.

  • Page 173: Instrument Identification

    6.7.12 Instrument Identification Identification Causes the lock-in amplifier to respond with the number 7270. Report firmware version Causes the lock-in amplifier to respond with the firmware version number, as also displayed on the Configuration menu.

  • Page 174: Auto Default And Calibration

    Chapter 6, COMPUTER OPERATION PAGE [n] Front panel display page number This command sets or reads the “page number” of the display on the instrument, for example PAGE 1 selects the Main Display. n lies in the range 1 - 11, 21 - 23, and 40 - 89.

  • Page 175: Programming Examples

    Chapter 6, COMPUTER OPERATION X[.] X1[.] X2[.] XOF[n XOF1[n XOF2[n XY[.] XY1[.] XY2[.] Y[.] Y1[.] Y2[.] YOF[n YOF1[n YOF2[n AQN1 AQN2 AXO1 AXO2 6.5 Programming Examples 6.5.01 Introduction This section gives some examples of the commands that need to be sent to the lock- in amplifier for typical experimental situations.

  • Page 176: Frequency Response Measurement

    Chapter 6, COMPUTER OPERATION required output. 6.5.03 Frequency Response Measurement In this example, the lock-in amplifier's internal oscillator output signal is fed via the filter stage under test back to the instrument's signal input. The oscillator frequency is stepped between a lower and an upper frequency and the signal magnitude and phase recorded.
  • Page 177 Chapter 6, COMPUTER OPERATION Now the curve storage needs to be set up: Clear and reset curve buffer CBD 19 Stores X channel output, Y channel output and sensitivity (i.e. bits 0, 1 and 4) LEN 1000 Number of points = 100 Hz × 10 seconds STR 10000 Store a point every 10 ms (10,000 µs) The data is acquired by issuing:...
  • Page 178 Chapter 6, COMPUTER OPERATION 6-40...

  • Page 179: Appendix A, Specifications

    Specifications Appendix Measurement Modes X In-phase Y Quadrature The unit can simultaneously show any R Magnitude four of these outputs on the front panel  Phase Angle display Noise nF, n  127 Harmonic Dual Harmonic Simultaneously measures the signal at two different harmonics F and F of the reference frequency...

  • Page 180: Reference Input

    Appendix A, SPECIFICATIONS Signal Channel Voltage Inputs Modes A only, -B only or Differential (A-B) 0.001 Hz  F  250 kHz Frequency Response Full-scale Sensitivity 2nV to 1 V in a 1-2-5 sequence (e.g. 2 nV, 5 nV, 10 nV) Input Impedance FET Input 10 M...
  • Page 181 Appendix A, SPECIFICATIONS Sinusoidal Input Level 1.0 V rms Frequency Range 0.3 Hz to 250 kHz Squarewave Input Level 250 mV rms Frequency Range 2 Hz to 250 kHz Reference Channel Phase Set Resolution 0.001º increments Phase Noise at 100 ms TC, 12 dB/octave slope Internal Reference <...
  • Page 182 Appendix A, SPECIFICATIONS 50  Output Impedance Sweep Frequency Output Range 0.001 Hz to 250 kHz Linear or Logarithmic Step Rate 1000 Hz maximum (1 ms/step) Amplitude Sweep Output Range 0.000000 to 5.000000 V rms Linear Step Rate 20 Hz maximum (50 ms/step) Auxiliary Inputs ADC 1, 2, 3 and 4 Maximum Input...

  • Page 183: User Settings

    Appendix A, SPECIFICATIONS Data Storage Buffer Size 100,000 data points max. Max Storage Rate Fast Mode 1 MHz (X1, Y1, X2, Y2, ADC1, Demod I/P 1, Demod I/P 2) Normal Mode 1 kHz User Settings Up to 8 complete instrument settings can be saved or recalled from memory as required Interfaces USB 2.0, Ethernet, and RS232 allow complete control of instrument settings, and...
  • Page 184 Appendix A, SPECIFICATIONS...

  • Page 185: Appendix B, Pinouts

    Pinouts Appendix B.1 RS232 Connectors Pinout Figure B-1, RS232 and AUX RS232 Connector (Female) Function Description Data In Data Out Signal Ground Request to Send - always +12 V All other pins are not connected B.2 Preamplifier Power Connectors Pinout Figure B-2, Preamplifier Power Connector Function –15 V...
  • Page 186 Appendix B, PINOUTS B.3 Digital I/O Port Connectors Figure B-3, Digital I/O Port Connector 8-bit TTL-compatible port. Each bit is configurable as an input or output. If configured as an output, the bit status can be set, and if configured as an input it can be read, from the front panel or via the computer interfaces.

  • Page 187: Appendix C, Cable Diagrams

    Appendix C.1 RS232 Cable Diagrams Users who choose to use the RS232 interface to connect the model 7270 lock-in amplifier to a standard serial port on a computer will need to use one of two types of cable. The only difference between them is the number of pins used on the connector which goes to the computer.
  • Page 188 Appendix C, CABLE DIAGRAMS Figure C-2, Interconnecting RS232 Cable Wiring Diagram...

  • Page 189: Appendix D, Default Settings

    Default Settings Appendix Auto Default Function The Auto-Default computer commands ADF 1 or ADF 2 set the model 7230's controls as follows:- Main Display Displays the AC Gain, full-scale sensitivity, reference phase, time constant, reference phase and oscillator frequency controls on the left-hand side. On the right- hand side, the display mode is set to two bar-graphs and two large digital displays, showing signal magnitude as a percentage of full-scale, X channel and Y channel outputs in volts and signal phase in degrees.
  • Page 190 Appendix D, DEFAULT SETTINGS Output Offset & Expand Offset Status Output Expand Output Equations ((X-X)  X)/X = zero Equation #1 ((X-X)  X)/X = zero Equation #2 Equns 1 & 2 C1, C2 Frequency Sweep Start Frequency 0.000 Hz Stop Frequency 0.000 Hz Step Size...
  • Page 191 Computer IP Address 000.000.000.000 USB Settings Terminator Null, Status & Overload bytes The ADF 2 computer command sets the model 7270's controls and output displays as for the ADF 0 command, except that the oscillator amplitude is set to 0 V rms.
  • Page 192 Appendix D, DEFAULT SETTINGS...
  • Page 193 Alphabetical Listing of Commands Appendix Fast Data Transfer command The ? command offers a method of reading a combination of instrument outputs which are sampled at the same time, thereby ensuring that they are correlated. The response to the ? command is the output(s), expressed in floating point mode, specified by the present setting of the Curve Buffer Define (CBD) command (see section 6.7.09) and separated by delimiter character(s) defined by the DD command.

  • Page 194: Appendix E, Alphabetical Listing Of Commands

    Appendix E, ALPHABETICAL LISTING OF COMMANDS AMDEPTH [n] Oscillator amplitude modulation dept control The value of n sets the oscillator amplitude modulation depth in percent, from 0 to AMFILTER [n] Oscillator amplitude modulation filter control command The value of n sets the oscillator amplitude modulation voltage low-pass filter control in the range 0 to 10.
  • Page 195 Appendix E, ALPHABETICAL LISTING OF COMMANDS in the range 0 to 5.000 V In fixed point mode, n is in microvolts rms and in floating point mode n is in volts AUTOMATIC [n] AC Gain automatic control Status AC Gain is under manual control, either using the front panel or the ACGAIN command Automatic AC Gain control is activated, with the gain being adjusted according to the full-scale sensitivity setting...
  • Page 196 Appendix E, ALPHABETICAL LISTING OF COMMANDS Bit Decimal value Output and range Ratio (±10000 FS) Log ratio (-3000 to +2000) ADC1 (±10000 = ±10.0 V) ADC2 (±10000 = ±10.0 V) 1024 ADC3 (±10000 = ±10.0 V) 2048 ADC4 (±10000 = ±10.0 V) 4096 DAC1 (±10000 = ±10.0 V) 8192...
  • Page 197 Appendix E, ALPHABETICAL LISTING OF COMMANDS Signal (DAC1) X % (2.5 V FS) Noise % (2.5 V FS) Ratio: (10 × X%/ADC 1) (10  X%/ADC1) Log Ratio: log Equation 1 Equation 2 User DAC1 Main signal channel ADC output (digital signal monitor 1) Magnitude2 % (2.5 V FS) (dual mode only) Signal (DAC2) Y % (2.5 V FS)
  • Page 198 Appendix E, ALPHABETICAL LISTING OF COMMANDS mode Standard Fast DAC[.] n Set user DAC output voltage controls The first parameter n , which specifies the DAC, is compulsory and is either 1, 2, 3 or 4. The value of n specifies the voltage to be output.
  • Page 199 Appendix E, ALPHABETICAL LISTING OF COMMANDS Output and range X Output (±10000 FS) Y Output (±10000 FS) Main signal channel ADC output (digital signal monitor 1 ADC1 (±10000 = ±10.0 V) ADC2 (±10000 = ±10.0 V) Dual modes only:- Output (±10000 FS) Output (±10000 FS) Input to second demodulator (digital signal monitor 2) The computer program's subroutine which reads the responses to the DC command...
  • Page 200 Appendix E, ALPHABETICAL LISTING OF COMMANDS Reference Frequency = (65536 × value in Curve 16) + (value in Curve 15) The computer program's subroutine which reads the responses to the DCB command needs to be able to handle the potentially very large data blocks (200 k bytes in the case of one 100 k curve) that can be generated.
  • Page 201 Appendix E, ALPHABETICAL LISTING OF COMMANDS Bit Decimal value Output and range Ratio (±10000 FS) Log ratio (-3000 to +2000) ADC1 (±10000 = ±10.0 V) ADC2 (±10000 = ±10.0 V) 1024 ADC3 (±10000 = ±10.0 V) 2048 ADC4 (±10000 = ±10.0 V) 4096 DAC1 (±10000 = ±10.0 V) 8192...
  • Page 202 Appendix E, ALPHABETICAL LISTING OF COMMANDS according to the following table: Variable Range X or X1 ±30000 Y or Y1 ±30000 MAG or MAG1 0 to 30000 PHA or PHA1 ±18000 ADC1 ±10000 ADC2 ±10000 ADC3 ±10000 ADC4 ±10000 0 to 100000 0 to 100000 10 0 zero...
  • Page 203 Appendix E, ALPHABETICAL LISTING OF COMMANDS EX [n] Output expansion control Expands X and/or Y channel outputs by a factor of 10. Changes bar-graphs, analog outputs full-scale to ±1000% if X or Y selected. The value of n has the following significance: Expand mode Expand X...
  • Page 204 Appendix E, ALPHABETICAL LISTING OF COMMANDS mHz. The range of n is 0 to 125,000,000 representing 0 to ± 125 kHz; in floating point mode n sets the span frequency in Hz. The range of n is 0 to 1.25E5. ...
  • Page 205 SWEEP command with a parameter of 9, 10 or 100, then this sweep will be stopped as well. Identification Causes the lock-in amplifier to respond with the number 7270. IE [n] Reference channel source control (Internal/External)
  • Page 206 Appendix E, ALPHABETICAL LISTING OF COMMANDS Selection INT (internal) EXT (external rear panel TTLREF IN input) EXT (external front panel analog REF input) IE2 [n] Reference channel 2 source control, Dual Reference In Dual Reference mode, the value of n sets the reference channel 1 source according to the following table: Selection INT (internal)
  • Page 207 Appendix E, ALPHABETICAL LISTING OF COMMANDS Selection Enable 50 or 60 Hz notch filter Enable 100 or 120 Hz notch filter Enable both filters Notch Filter Center Frequencies 60 Hz (and/or 120 Hz) 50 Hz (and/or 100 Hz) LOCK System lock control Updates all frequency-dependent gain and phase correction parameters.
  • Page 208 Equivalent to the compound command MAG[.];PHA[.] \N n Address command When the model 7270 is daisy-chained with other compatible instruments this command will change which instrument is addressed. All daisy-chained instruments receive commands but only the currently addressed instrument will implement or respond to the commands.
  • Page 209 Appendix E, ALPHABETICAL LISTING OF COMMANDS NHZ. Causes the lock-in amplifier to respond with the square root of the noise spectral density measured at the Y channel output, expressed in volt/Hz or amps/Hz referred to the input. This measurement assumes that the Y channel output is Gaussian with zero mean.
  • Page 210 Operation is the same as earlier SIGNAL RECOVERY lock-in amplifiers, such as the models 7220, 7225, 7265, 7265, 7280, 5209 and 5210. Operation is the same as earlier versions of firmware in the models 7270, 7124 and 7230 PORTDIR [n]...
  • Page 211 Appendix E, ALPHABETICAL LISTING OF COMMANDS REFN [n] Reference harmonic mode control The value of n sets the reference channel to one of the NF modes, or restores it to the default 1F mode. The value of n is in the range 1 to 127. REFP[.] [n] Reference phase control In fixed point mode n sets the phase in millidegrees in the range ±360000.
  • Page 212 Appendix E, ALPHABETICAL LISTING OF COMMANDS full-scale sensitivity IMODE=0 IMODE=1 IMODE=2 2 nV 2 fA 5 nV 5 fA 10 nV 10 fA 20 nV 20 fA 50 nV 50 fA 100 nV 100 fA 200 nV 200 fA 2 fA 500 nV 500 fA 5 fA...
  • Page 213 Appendix E, ALPHABETICAL LISTING OF COMMANDS Slope 6 dB/octave 12 dB/octave SRATE[.] [n] Oscillator frequency and amplitude sweep step rate In fixed point mode, sets the sweep rate in milliseconds per step, and in floating point mode sets the rate in seconds. The range of n is 1 to 1000000 (1 ms to 1000 s) Report status byte Causes the lock-in amplifier to respond with the status byte, an integer between 0 and 255, which is the decimal equivalent of a binary number with the following bit-...
  • Page 214 Appendix E, ALPHABETICAL LISTING OF COMMANDS and/or amplitude sweeps to the curve buffer. The SWEEP command continues to function as a write/read command except when the curve buffer acquisition is actually running. In such cases, the SWEEP command changes to read-only and will only report values of 9, 10 or 11, indicating what type of linking is active.
  • Page 215 Appendix E, ALPHABETICAL LISTING OF COMMANDS NOISEMODE NOISEMODE NOISEMODE NOISEMODE = time constant time constant time constant time constant 10 µs 20 µs 50 µs 10 s 100 µs 20 s 200 µs 50 s 500 µs 500 µs 100 s 1 ms 1 ms 200 s...
  • Page 216 Appendix E, ALPHABETICAL LISTING OF COMMANDS TDT n Take data triggered Sets the instrument so that data acquisition is initiated on receipt of various trigger conditions at the TRIG connector on the rear panel. If an oscillator frequency and/or amplitude sweep has been defined and linked to the curve buffer using the SWEEP command with a parameter of 9, 10 or 11, then this sweep will be started as well.
  • Page 217 Appendix E, ALPHABETICAL LISTING OF COMMANDS Report firmware version Causes the lock-in amplifier to respond with the firmware version number, as also displayed on the Configuration menu. VMODE [n] Voltage input configuration The value of n sets up the input configuration according to the following table: Input configuration Both inputs grounded (test mode) A input only...
  • Page 218 Appendix E, ALPHABETICAL LISTING OF COMMANDS E-26...
  • Page 219 Index Index ? command 6-20, E-1 ASTOP[.] [n] command 6-21, E-2 \N n command 6-34, E-16 Auto functions 8-bit programmable output port 3-15 Auto-Default 3-17, 5-29 A input connector 4-1 Auto-Measure 3-17, 5-7, 5-28 AC Gain Auto-Measure 1 5-63, 5-81 and Auto-Measure 3-17, 5-28 Auto-Measure 2 5-63, 5-81 and Auto-Sensitivity 5-28...
  • Page 220 INDEX for internal oscillator 6-20 DCT n command 6-32, E-8 for reference channel 6-13 DD [n] command 6-34, E-9 for signal channel inputs 6-10 DEFEQU [n ] command 6-19, E-9 for signal channel output amplifiers 6-17 Delimiters 5-33, 6-4, 6-6, 6-9 for signal channel output filters 6-15 DEMOD 2 Sourcecontrol 5-12 Common mode rejection ratio (CMRR) 3-3...
  • Page 221 INDEX Default Gateway control 5-34 Harmonic 2 phase control 5-81, 5-84 home page 6-7 Harmonic 2 phase quadrant control 5-81 IP Address 6-7 HC command 6-30, E-13 IP Address control 5-34 HELP Key 4-5 Overload byte 6-8 ID command 6-35, E-13 sockets 6-8 IE [n] command 6-13, E-13 Status byte 6-8...
  • Page 222 INDEX NN[.] command 6-19, E-17 offset status control 5-16, 5-70, 5-71, 5-87, 5-89 NNBUF [n] command 6-15, E-17 output expansion 3-12 Noise Buffer Length control 5-30 output offset 3-12 Noise Measurement Mode 5-30 sync time constant control 5-68, 5-85 Noise measurements 3-13 time constant 2 control 5-86 NOISEMODE [n] command 6-15, E-17 time constant control 5-14, 5-68, 5-69, 5-85...
  • Page 223 INDEX Relock External Reference control 5-7, 5-62, 5-81 Output Filters Menu 5-14 REMOTE [n] command 6-35, E-19 Output Offset & Expand Menu 5-15 Remote indicator 5-5 Reference Channel Menu 5-12 RS [n ]] command 6-33, E-19 Signal Channel Menu 2 5-10 RS232 interface SLOPE [n] command 6-16, E-20 address control 5-32...
  • Page 224 INDEX Serial Number descriptor 5-35 described 3-2, 5-8 Status byte 6-6 Main Display 5-59 Status indicator 5-36 manual setup 5-58 Terminator 6-6 setup menus 5-56 USB Operation 6-5 virtual lock key 5-58 USB Status Menu 5-35 VMODE [n] command 6-10, E-25 USBTERM [n] command 6-34, E-24 VRLOCK [n] command 6-15, E-25 User Settings Menu 5-49...
  • Page 225 This Warranty shall not apply to any instrument or component not manufactured by AMETEK Advanced Measurement Technology, Inc. When products manufactured by others are included in AMETEK Advanced Measurement Technology, Inc equipment, the original manufacturers Warranty is extended to AMETEK Advanced Measurement Technology, Inc customers.

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