I want to measure the V-I time lag (and hence power factor) exhibited by a material that can be modelled as a capacitance. This is connected across 110V AC at 50Hz. From this my intention is to calculate (and build) the compensating inductance.

1. The capacitor is powred by an AC-AC convertor (240 V in, 110V out) showing cos ( phi) = 0.73. Does this indicate the worst case power factor that the convertor can correct?

2. Must I use RMS values or peak values of voltage across the capacitor in order to calculate the apparent power?

3. I am measuring the voltage across the capacitor using the pseudo differential (A-B) technique. In order to do this, I have connected the references of 2 scope probes together (not to ground). Is this correct?

4. I thought that probe references are connected internally to the scope earth? Is this not so?

(Previously when I tried to float the scope the circuit breaker did trip. I now realise floating a scope is not the right thing to do).

Any advice much appreciated...