Author Topic: Would it be possible to mod the maximum test voltage for the diode test on DMMs?  (Read 479 times)

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Offline Decoman

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Looking at the manual for the UT61E multimeter, it seems to be pointed out that the maximum test voltage for the diode test is 2.8V. Or am I wrong in thinking this?

An EEVblog video seem to point out that you would want a value of 4V on a good multimeter, and I am reading how doing the diode test with some LEDs, only light up the diode, but does not show any value for a measurement. So I am thinking that this multimeter has perhaps a too low max voltage for the diode test. And correct me if I am wrong in thinking that.

Could there be a way to mod this value to something higher on a multimeter? I am going to guess that it is not possible to easily improve on this built in feature, but I want to ask anyway.

I want to add that my interest for this is that I will be working with LEDs.
« Last Edit: December 09, 2017, 05:26:32 pm by Decoman »

Offline retrolefty

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I suspect that one can't practically modify one's meter. However it might be interesting to see what wiring a 3 vdc battery in series with the diode(s) under test to see if that raised the effective maximum test voltage?


Offline madires

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The diode test uses a 1mA constant current source usually. If the voltage range supports higher voltages and the current source is external (not included in the chipset) it might be possible to hack something. But for LEDs I'd build a constant current source with selectable current (5/10/20mA) and use the DMM in voltage mode to measure Vf.

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