A SIMPLE MANUAL CURVE TRACER using microcontroller
Measure current vs voltage or voltage vs current over limited range with good accuracy
This was built on a phenolic board which was mounted on a plastic box.
The box serves two purposes: It holds the circuit off the workbench, and
it makes a nice, stable mount for the potentiometer.
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I realized that soon I am going to have to measure the voltage as a function of current for a lot of little devices. Having done quite a few using clip leads and resistors, and wanting to make things a little easier on myself, I put together the curve tracer described on this page.
Current as a function of voltage for a infrared LED. Horizontal axis is 200 mv/ division
and the vertical axis is 1 ma per division. The knee is seen to be pretty sharp at 1 volt.
In the case of this measurement, the oscilloscope was adjusted to place the origin in the
lower left hand corner of the screen.
Using this fixture, I can easily measure the IV curves of components in two quadrants. If I want to see the curve in the other two quadrants, I can reverse the device’s connections and adjust the centering on the scope accordingly. This can also be used with voltmeters, especially when a high degree of accuracy is requited.
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