Measuring Capacitor ripple current

[fxdif]

Hi,

How can I measure the ripple current through a capacitor? Can I just use an ammeter?

Thanks

 

[electricuwe]

Do not use an meter to measure ripple in a capacitor. The impedance of the meter will reduce the ripple current significantly, especially if there are several capacitors in parallel. Use a current probe or a current transformer instead. In some applications (SMPS output filter capacitors) even this adds to much impedance.

 

[Warpspeed]

All very true. The only real detrimental effect of ripple current is capacitor heating, as long as the capacitor remains within its allowable maximum temperature, ripple current will be sufficiently low.

So try measuring temperature rise of those high frequency caps rather than the actual ripple current. Also, any current measurement will need to be a true RMS measurement to be meaningful, ripple currents are almost never sinusoidal.

As electricuwe says, inserting something in the current path can be very difficult and often misleading, especially on a compact multilayer circuit board.