Suppose we have a simple DC power source charging a battery or capacitor.
If we try to measure the capacitor's voltage in this simple circuit we will instead read the power source voltage:
Is it possible to directly measure the voltage of the capacitor without disconnecting the power source and without knowing the capacitor's time constant and capacitance?
I.e., I'm wondering if there's a circuit that can accomplish this without exploiting the following solutions:
- If we temporarily disconnect or turn off the power source, the voltmeter will read the voltage across the capacitor.
- If we know the time constant and capacitance we could instead connect an ammeter and deduce the capacitor's voltage from that. (Or, if we knew it was fully discharged initially, we could integrate the amperage from the start of charging to calculate its voltage.)
I've been trying to picture some clever arrangement of diodes that might allow for measurement during charging, but that has left me thinking that this is theoretically impossible using a static circuit.