Loss of Trust

Not in a person or an institution but a DVM.  My Metex ME-11 DVM, bought from Radio Shack mail order in the 20th century.  I bought it because it had an RS-232 port.  I think I might have used that feature once and then never again :)

Metex shown here measuring for a diode on a PIC pin

It's kind of like Star Trek The Next Generation: in the first episode the Enterprise gets split into the saucer section and the engineering section - can't even remember why - but I don't think it was ever done again - maybe they did it more, I wasn't that faithful a viewer or rememberer !

Back to the DVM: today I was testing some BAT85 diodes for forward voltage from two different batches.  The first batch produced measurements in the 600 mV range - which seemed wrong.  So I tried the second batch and got readings in the 340-370 mV range - these seemed more reasonable since the BAT85 is a Schottky diode.  So I fumed a little, I had bought the diodes a while back on Ebay and thought I had been stuck with plain 1n4148 diodes (non-Schottky).

But then I retried the first batch and got readings in the 291 to 298 mV range - this is much better !  I didn't get the wrong diodes after all - it was the Metex (or the probes).

I also redid the other batch and the readings were now in the range from 287 to 294 mV.

So the next step will be to get some Deoxit and see if a little on the selector switch and banana jacks helps restore performance (and trust).  If that doesn't do it, maybe it is time for a new DVM ?
 
Best Regards,
Chuck, WB9KZY
http://wb9kzy.com/ham.htm