Potentiometer Testing

[nukeman]

I have a 2W, 500 ohm potentiometer that has erratic resistance readings. Does anyone have a good web link for testing pots? I was thinking about setting up a test rig to put voltage across the pot and monitor the voltage drop across the pot (or across an in-series shunt) as the pot is cycled.

 

[buzzp]

Cant help with any links but if you have erratic resistance readings, the pot is bad.
If you push on the pot as you turn it and dont get erratic readings then the wiper is loose.

 

[OperaHouse]

Often a squirt of WD-40 lubricant will clean these up for a while. Seems to work just as well as pot & contact cleaners. If the pot is sealed, replacement is the only option.

 

[Rakestraw]

Many times if the pot gets dirty and is not cleaned up reasonably soon the dirt will damage the pot. A 2 W pot is usually wire wound and is not as susceptible to this kind of damage.
If you have many pots to test one of many viable test setups would be a 3 resistor voltage divider using the pot as the center resistor, a 2W pot can pass a fair amount of current but 5ma should be adequate for a test. You will then need to monitor the voltage at the wiper with an analog meter (or a digital meter with an analog bar graph) and slowly rotate the pot from end to end, and apply a slight up/down force on the shaft if the pot is good you should see only smooth voltage changes on the meter.

 

[sdmays]

Is this a linear trim-pot or a logarithmic trim-pot?

 

[automatic2]

Replace the pot. If your erratic condition is overcome, you've performed your test and have found it to be faulty.

 

[uWaveFDL]

Monitor the voltage change with an o'scope. It will display any discontinuities in voltage change.

 

[maxIminE]

Noisy pots have been around forever! One test we used on audio equipment years ago was to use the pot as a voltage divider, but, place a small audio transformer (Lo-Z side) in series with pot. Connect the other transformer winding (Hi Z)to an audio amp, or maybe even Hi-Z headphones. Now you can and hear the noise! It is more sensitive than a 'meter wiggle'. Coupling caps might also work instead of a transformer. For this application, junkbok parts are entirely 'In Spec'!