Trim pots

[Twothumbz]

I recently tried to substitute standard sized pots for the tim pots on a circuit board. I was unable to determine which of three tabs was the wiper. I have a Vellman meter and was getting no readings at any setting. Thinking that the meter may be bad, I then put it across a standard resistor and got an accurate reading. I tried them same thing on the pots I was intending to use and got nothing again. Why would a meter get readings on one, but not the other?

TwoThumbz

[AL]

Not sure about the meter but there is some info on pots in the DIY FAQ section at the top of the page. If you have the pot hooked up backwards it will just work in reverse - not that big of a deal really albeit confusing at times.

AL

[petemoore]

Wipers in the middle...
 Check out GEO secret life of Pots.
 Linear pots will be same same either way you hook up the outside lugs, except you will turn the Shaft CCW instead of CW if you invert the outside lug connections [potlugs 1 and 3]
 Log pots.. .. read the GEO article. Basically have alot of the difference of R Value dividing 'bunched up' at one end of the shaft range of travel..for volume controls [and some other stuff] this makes the travel match what you hear in terms of evenly going up througout the 0 to 10 travel of the potshaft...for use as a gain control, the same resistances are provided, but the knob might have all the useful settings in about 1/4 of the CCW to CW range of the potshaft.
 I could proofread and correct a bit...this should give you an idea about pots...the GEO article should clear up anything I didn't say so good...

[octafish]

Just so you know, pots can be destroyed by heavy handed soldering. Trust me I know. The prongs transfer heat into the pot and damage internal connections. I don't know if I am the only person cack handed enough to actually do this, but once you know it can happen you tend to take a bit more care with your pots.

[Paul Perry (Frostwave)]

Octafish is right, in particular some of those blue rectangular multi-turn trims seem to have a fairly low melting point plastic case :oops:
I've never personally seen a trimpot where the centre pin wasn't the wiper.