Measuring the resistance of an RC circuit

[santiago_89]

Hi everybody. I'm trying to find the power to gound resistance of a couple of resistive circuits but they each are in parallel with a capacitor. The meter reads a very high value when the cap charges up completely. Is this still a usable reading? Or, to put it another way, will the measured resistance be different if the resistive circuit was shorted?

[kenray]

once the caps are charged you should be reading the resistance of the resistors.

[torbjorn]

Yes, in most cases the readout will be correct once the capacitors are charged. However, there are some instruments (only seldom on ordinary DMMs but more common on specialized RCL meters) that either use AC or short DC pulses for the resistance measurements. Those will give a wrong reading when measuring on RC circuits.
You can check it out by several methods:
1) Study the operating manual for the meter.
2) Try measuring the resistance of a single resistor and then connect a capacitor of similar value to your "real" circuits in parallell, check if the reading changes.
3) Check with an oscilloscope if the meter only supplies pure DC or if there are any pulses or AC components superposed on it.