Electronics > Projects, Designs, and Technical Stuff

Panel Meter Ref. Pots

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engrguy42:
I've got a cheapo panel meter (V/I) I'm going to use with my power supply remodel, and I noticed it's quite a bit off compared to my multimeter. Amps show 0.0 when it's actually 0.1, and voltage is low by maybe 0.5 volts or so sometimes. Maybe that's within specs, not sure I care.

Anyway, I noticed some super tiny reference pots with metal casings, one for V and one for I. So I figured what the heck lemme see if I can tweak them.

Turns out when I touch the pot with my metal screwdriver the amps reading goes thru the roof. Like up near max rating of 30A. Apparently they want a plastic screwdriver or something? Good luck finding a tiny plastic screwdriver....

Is this normal and I'm just out of the loop?

Thanks.

ColdKeyboard:
Can you maybe share some pictures? :)

schmitt trigger:
Back when radios and TVs had tuneable RF and IF stages, assembly lines employed plastic or ceramic screwdrivers to tune the variable inductors, capacitors and trim pots.

Repair shops would also use them.

I haven’t seen them since the late 80s.

WattsThat:
It’s picking up mains noise conducted through you.

As mentioned, you need a non-conductive adjustment tool. Search eBay for “ceramic screwdriver”, tons from China for a buck apiece or thereabouts.

ITman496:
We have a million different kinds of those at my office (land mobile radio business) so I kind of forgot how rare they are.  I forget where we get them, most of them are older then I am and say motorola on them!

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