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Curve Tracer Adaptor(LM555)

2017-08-06 18:01  
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This article briefly describes the Curve Tracer Adaptor (LM555). Although this circuit is very easy to understand, but also very practical. Circuit elements in depth understanding of the grasp of the principle is very effective. Do you know the circuit, you can see and purchase these components: LM555 .

This unit employs a dual trace oscilloscope with X-Y function as a display to test and demonstrate the action of circuits and components such as transistors, diodes, zener diodes, and terminated and unterminated transformers. A low frequency sinewave (ie 10Hz – 1kHz) is applied to op amp IC2a via potentiometer VR1 to set the “X” and “Y” levels for the X-Y display on the scope. The output of IC2a is applied to the X input via R4 and IC2b and also to Probe 1 via the contacts of relay 1. IC2b provides a low impedance drive for the X input and also isolates the X input cable capacitance from probe 1. The current flowing into the probes develops a voltage across R4 which is processed by IC2d and applied to theCROY input to represent current.


Figure:1 Curve Tracer Adaptor

Figure 1 Curve Tracer Adaptor


The scope display thus represents an X-Y graph where voltage across a circuit under test is displayed on the X axis (horizontal) and the current though it displayed on the Y axis (vertical). With a calibrated scope this equates to 1mA/V. IC1 and a relay are included to enable two probes to be used and comparisons made between a known good device and a faulty one. The relay should be a low capacitance reed type. By using the scope’s X and Y gain controls, the sinewave applied to the device under test should be adjustable from a few millivolts up to 24V peak-peak to get a very useable display.

 

Thus, the unit can be used on voltage sensitive devices and at the other end of the scale apply enough voltage to check the operation of, say, a 10V zener diode. Note that all devices should be tested in the unpowered condition. If used for in-circuit tests, the effects of circuit components will need to be taken into account. Shielded coax leads should be used for the X and Y inputs and the probe leads should have zero resistance. Normal scope probes should not be used as these usually have significant built-in resistance which will interfere with measurements.
 

 


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