Summary of Contents for Syscomp CTR-201
- Page 1 Syscomp Computer Controlled Instruments CTR-201 Curve Tracer Syscomp Electronic Design Limited http:\\www.syscompdesign.com Revision: 2.1 November 2017...
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Page 2: Table Of Contents
Contents 1 Introduction 2 The CTR-201 Curve Tracer 3 Measurements Device Connections ......... - Page 3 List of Figures VI Characteristics ......... . . Typical Control Panel .
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Page 4: Introduction
1 Introduction Electronic devices are useful because they cause a specific relationship between voltage and current. A curve tracer displays the VI characteristic of these devices, leading to better understanding of their operation. (a) Resistor, 1kΩ (b) Diode, MR851 Figure 1: VI Characteristics As a very simple example, it’s possible to plot the VI characteristic of a resistor on a curve tracer. -
Page 5: The Ctr-201 Curve Tracer
The CTR-201 system uses a completely different approach. The test hardware connects to a personal computer via USB, and the computer runs a control program to operate this hardware. The hardware unit contains various controlable voltage and current sources that actuate the device under test while measuring the voltages and currents in the device. - Page 6 The data can be captured and transferred to a spreadsheet or other program for further analysis. • Because the CTR-201 hardware is hosted by a computer it is straightforward to capture screen shots, save the data to a file for further analysis, or project the screen image in a teaching environment.
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Page 7: Measurements
3 Measurements 3.1 Device Connections 3.2 Instrument Overview Figure 2: Typical Control Panel A typical control panel configuration is shown in figure 2. Some sections of this display change according to the type of device under measurement. Here we list the various functions on the control panel of the Curve Tracer. These are the functions that apply to all measurements. - Page 8 Menu Bar: Tools Calibration Provides access to the calibration facility of the curve tracer. You will need multiple digital volt- meters and ammeters to complete this process. Extreme caution is required. Menu Bar: Data Save, load and clear reference trace. This allows saving and displaying a trace for comparison purposes. Menu Bar: Hardware Connect Provides access to the routine for connecting to a USB port on the host computer.
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Page 9: Cursors
Voltage-Mode, Current Mode The VI measurement setting allows one to set the measurement mode. In Voltage mode, the instrument adjusts the terminal voltage and measures the current. In current mode, the instrument adjusts the current and measures voltage. For example, in a diode-like device, when measured by voltage mode the current increases very rapidly after the device threshold is reached. -
Page 10: Diode
3.3 Diode The control settings for a typical diode measurement, and the results of that measurement, are shown in figure 4. (a) Control Settings (b) Result Figure 4: Diode A diode VI characteristic could be measured by placing a voltage between its terminals and measuring the current (voltage-driven), or passing a current through it and measuring the terminal voltage (current-driven). -
Page 11: 1N3022 Zener Diode
(a) Forward (b) Reverse Figure 5: 1N3022 Zener Diode... -
Page 12: Npn Transistor (Bjt)
3.5 NPN Transistor (BJT) The control settings for an NPN Power Transistor (2N3055), and the results of that measurement, are shown in figure 6. (a) Control Settings (b) Result Figure 6: NPN Transistor Notes • The collector current of a BJT is more-or-less constant with increasing collector-emitter voltage. That is, it behaves as a current source (or, more accurately, a current sink in the case of an NPN transistor.) Consequently, it is best to test this characteristic by setting a base current, sweeping the collector-emitter voltage and measuring the collector current. -
Page 13: Pnp Transistor (Bjt)
– Use the Current Limit or Power Limit setting to protect the transistor from excessive current. If the collector current tries to exceed this value, the measurement halts and the measurement currents and voltages are removed. – Because the measurement is pulsed with time between each pulse, it may be possible to exceed the actual power dissipation of the device without destroying it. -
Page 14: P-Channel Mosfet
(a) Control Settings (b) Result Figure 8: N-Channel MOSFET an internal impedance of 4k7Ω. (The DC impedance of a MOSFET gate is essentially infinite, so the internal impedance of this voltage source is inconsequential.) 3.8 P-Channel MOSFET For an P-Channel MOSFET, setup and operation of the curve tracer is similar to the N-Channel MOSFET, de- scribed previously. -
Page 15: P-Channel Mosfet
(a) Control Settings (b) Result Figure 9: P-Channel MOSFET (a) Control Settings (b) Result Figure 10: N Channel JFET... -
Page 16: General 2-Terminal Measurement
3.10 General 2-Terminal Measurement For general voltage-stimulus measurement, use the 2-Terminal setting. This measurement operates in voltage mode, where the voltage is adjusted and the current measured, and current mode, where the current is adjusted and the device voltage measured. 3.10.1 2-Terminal Measurement, Voltage Mode This measurement is capable of sweeping from a negative to positive voltage while plotting the device current, so that all quadrants are visible. -
Page 17: 2-Terminal Measurement, Current Mode
3.10.2 2-Terminal Measurement, Current Mode This measurement is similar to the 2-terminal voltage mode, with the difference that the current is controlled and the voltage measured. The maximum range of current is +/-1 amp and the resultant voltage +/-40V. Notice that the device connections are different for voltage and current mode. A warning dialog pops up when switching between them. -
Page 18: Lambda Diode, Negative Resistance Device
Consequently, the device should be driven by a constant voltage source, while measuring the current. In the CTR-201, that implies connecting it between the collector (Red) and emitter (Black) terminals, which are both voltage sources. The current drive (Blue) terminal is not used. -
Page 19: How It Works
(a) Control Settings (b) Result Figure 14: 2N4403 PNP BJT 4 How It Works A block diagram of the curve tracer is shown in figure 20. It consists of two programmable voltage sources and one programmable bidirectional current source. These sources are controlled by 12 bit D/A converters. The measured voltages and currents are shown conceptually on the diagram as voltmeters and ammeter. -
Page 20: 2N7000 N-Channel Mosfet
It then sends the acquired data to the host, for display and storage. Commands are in the form of ASCII strings, so it is quite straightforward for some other software to control the CTR-201 hardware. Example: Diode Measurement A diode is connected with the anode connected to the Base terminal and the cathode to Collector terminal. -
Page 21: Solar Cell
(a) Control Panel (b) VI Characteristic Figure 16: Solar Cell Blue Black ........ -
Page 22: Lambda Diode
(a) Control Settings (b) Result Figure 18: Lambda Diode Figure 19: Vaccum Tube... -
Page 23: Curve Tracer Block Diagram
........Collector Voltage Drive .. -
Page 24: Calibration
5 Calibration (a) Ground Point (b) Attaching to Ground Figure 21: Attaching to the Ground Point... -
Page 25: Calibration Panel
The curve tracer is supplied in calibrated form. It shouldn’t be necessary to do a re-calibration, but we supply the information in this section. The curve tracer should not be operated in the uncalibrated state. It will generate incorrect results and may cause damage. -
Page 26: Installing The Software
There may also be subdirectories, such as Images and bin. At the time of writing, Syscomp was the only oscilloscope and waveform generator company providing source code for its products. Images contains various icons in image format (such as gif). bin contains the executables, for the different operating systems. These... -
Page 27: Installing The Tcl Interpreter On A Windows Machine
7 Commands Cautionary Note The CTR-201 Curve Tracer is designed to measure device characteristics by applying a voltage and measuring the resultant current, or vice versa. Using computer control, the applied voltage or current can be of very short duration. This minimizes the dissipation in the device and in the curve tracer drive circuitry. -
Page 28: Testing The Commands
7.1 Testing the Commands It is possible to communicate with the CTR-201 hardware using a terminal emulator program. Under Linux, communication was established with the CTR-201 software using the Cutecom terminal emulator. Settings for the emulator: Device /dev/ttyUSB0 Baud rate... - Page 29 Base output voltage to 10V The exact values of these messages depend on the calibration of the hardware and will vary between different CTR-201 units. Determining these values on your hardware gives the relationship between the command value and the output voltage.
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Page 30: Export And Import Data, Compare Measurements
Upgrading to the Latest Version Software can be upgraded at any time by downloading the latest version from the Syscomp website, in the Downloads section. Under a Windows operating system, download and run the installer program. Follow the commands and the software should install automatically. -
Page 31: Pulsed Vi Measurement
Figure 23: BJT Comparison 7.5 Pulsed VI Measurement This option was provided to a customer to minimize power dissipation in the device under test. With this option selected, the measurement of each point should be about 7.5ms long. The curve may be a bit noisier as we are doing less averaging in the firmware. -
Page 32: V Power Enable/Disable
Figure 24: 48V Power Enable/Disable...
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