U1: Pin4 - Pin6 measuring weird voltage

[hduncan]

It starts out at 161mv, then swings to -60mv, then 100mv, then -47mv, then slowly climbs to 5mv and I think it will keep going but I cant keep my arms still long enough.


Just to make sure: Negative probe goes to Pin4, and Positive goes to Pin6, right?

I mean, the point is to get it to 0V, which technically I have, (R16 is all the way rotates back until its clicking) but I still have some decimal spaces to hunt down.

Or should I not be worrying about rogue mv?

[hduncan]

Also, the DMM I am using seems to be working fine, though its really old.

When I have it set to mv voltage mode and DC voltage with the probes touching nothing, it fluctuates +/-28mv... is this normal or is this thing too old?

[hduncan]

ok now I'm reading a solid -69mv

[hduncan]

Alright people. I think I figured it out. I think these probes are old and not making good connection anymore. When i ground them down a bit to reveal fresh metal, I started getting more solid MV readings.

I really cranked R16 clockwise over and over and over a LOT and finally got it to read a pretty stable -0.6 mv.

[tpryan]

http://www.mcmelectronics.com/product/P ... 2-/201-120