How Can I Accurately Measure Voltage Drop across a Capacitor?

[simoncastle]

Hi all,

Here's the problem!

I am attempting to create a leakage current test suite. Basically it centers around cutting the voltage reference supply to a capacitor and measuring the voltage drop. Similar to the one in the attachment.

I figured that to determine the drop it would be a simple case of V at start minus V after time delay.

However a colleage told me that because of the exponential decay of capacitors this simple equation wouldn't be enough to accuratly determine the voltage drop.

Any ideas?

Thanks!

- Si

 

[Redbelly98]

I'm assuming you want to measure the parallel resistance (which causes the charge to leak) of the capacitor.

You can use an exponentially decaying function for the voltage:

$$V_t = V_{ref} \ e^{-t/(RC)}$$
where Vt is the voltage after t seconds. Solve the equation for R after measuring all other quantities (Vt, Vref, t, and C)