physics stack exchange

Many multimeters have a setting for measuring capacitance. The multimeter I have has a precision of four significant figures, or in other words, it returns the value in the form of 00.00 nF. However, I have found that for larger capacitance measurements the value oscillates quite a bit whereas for lower capacitance measurements it appears to be quite stable. In short, I would like to know of a method for quantifying this uncertainty, preferably using partial derivatives for the error estimation.

Cheers

New contributor
Jorge Romeu is a new contributor to this site. Take care in asking for clarification, commenting, and answering. Check out our Code of Conduct.
  • Welcome New contributor Jorge Romeu! Do you know how your multimeter is measuring capacitance? – Alfred Centauri 2 days ago

For "large" values of capacitance (greater than about 10 microfarads), the capacitor is usually of the electrolytic type and the dielectric used in them results from an electrochemical reaction which takes place when a voltage is applied to its terminals.

In practice, this means that for small values of the applied voltage, it's possible for the its capacitance to "wander" around until the electrochemistry locks in and stabilizes its behavior.

It also means that if the applied voltage is opposite to the marked polarity of the capacitor, the electrochemical cell that creates the dielectric will be driven backwards, destroying the dielectric layer and furnishing meaningless capacitance measurements in the process.

Finally, note that for very large values of the capacitance (hundreds of microfarads or more) your test meter may not be able to inject enough current into the capacitor to pump its voltage up sufficiently for the meter to deduce its capacitance.

Your Answer

Jorge Romeu is a new contributor. Be nice, and check out our Code of Conduct.
 

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.

Not the answer you're looking for? Browse other questions tagged or ask your own question.