C and L of potentiometers?

[Christer]

Does anybody have any idea of typical values for capacitance and inductance of potentiometers? I have been looking at datasheets for various potentiometers from at least six different brands, and there is never any info on this or any related parameter. I am primarily interested in ordinary, panel-type potentiometers, not trimmers (although such info is welcome too). I suspect C and L wouldn't change much depending on resistance value, and maybe not much with resistive material either. The physical design will matter of course, although I suspect most pots to be so similar in design that they do not have very large variations.

[Conrad Hoffman]

I did a couple quick measurements on a 10K Allen Bradley panel mount pot, starting with a vector impedance meter. The internal strays for the resistance element are negligible if you intend to connect the pot using wires or traces. Expect a few degrees of capacitive phase shift at 1MHz- my measurements were contaminated by the very short connecting wires, but that's my guesstimate when comparing with a 1/4W 10K MF resistor. There was no connection to the shell.

The real issue is capacitance to the metal shell of the pot, which is invariably grounded to the panel. On a 1615 bridge, the capacitance between one end of the element and the shell was 17.8pF with a D of 0.14 at 1kHz, series model. There was no wiper connection. Worth thinking about if one is using high values.

[Christer]

Thanks Conrad,

it sounds like the answer is "very small" and not surprising.

I didn't think of the capacitance to the metal shell, so that is a good point. On the other hand, many, or even most, pots nowadays come in plastic housing.