Project I Circuit principles Some basic circuit principles Capacitors reduce to open circuits at dc . Ohmmeter measurements are dc measurements, so they give you information about the resistors independently of the capacitor. Voltage division ratios give you information about resistance ratios. A capacitor in parallel with a resistor has no effect on such a measurement if the source is dc.
Capacitors reduce to short circuits at high frequency .
Measuring a voltage division ratio with an ac signal source applied at appropriate terminals of the box may give you enough information to calculate a resistance ratio that could not be found with a dc source applied. With these circuits, that should happen below 40kHz in any case. The regular coax cables have enough internal capacitance of their own to cause significant errors due to their loading effect on the circuit. The time-constant is a property of the network as a whole, and appears in all waveforms to be seen in the network. The appropriate signal source waveform is the square wave, which can be represented as a series of step functions of alternating positive and negative amplitude, separated by the half-period of the wave.