Hi All,
We need to measure some capacitors in powered mode. Unfortunately the 3070 does not have standard possibilities for this.
Does someone have experience with capacitor measurements in powered mode with use of the acv source and the serial resistor ?
The Accuracy must be around 1%
Does someone does have experience with other methods ??
thanks
Marco
We need to measure some capacitors in powered mode. Unfortunately the 3070 does not have standard possibilities for this.
Does someone have experience with capacitor measurements in powered mode with use of the acv source and the serial resistor ?
The Accuracy must be around 1%
Does someone does have experience with other methods ??
thanks
Marco
I have no direct experience of trying this, and when I first saw it a few days ago my immediate reaction was that without being able to measure phase it wouldn't be possible. However after further thought there might be some mileage to a simple 'potential divider' approach with the capacitor under test and one of the source termination resistors, which I think is what you are suggesting.
Assuming one end of the cap is grounded, if Vout is the voltage measured at the other end, then running through the maths I make the capacitance, C, to be:
C = sqrt[(Vs/Vout)^2-1]/(2*pi*f*R)
where R is the termination resistor, Vs the source voltage, and f the source frequency. A quick SPICE simulation with C = 47n, f = 1kHz, R = 5k and Vs = 1Vrms gives Vout around 560mVrms, and the calculation comes out close: however my guess is that you will be unlikely to get 1% accuracy from it.
So I think it might be worth trying, but it ignores all sorts of things like what the phase really is, and you cannot nullify the effects of parallel impedance paths with guarding as you can with the standard (unpowered) capacitor test. If you are looking to measure the caps for some sort of 'calibration' purposes, then I suspect you might be better off bolting-on some other sort of measurement means to specifically do this (?).
Tim