I'm trying to measure the reverse leakage current of some diodes with the method proposed HERE - the diode is connected in reverse bias to 5V through 1 megaohm and voltage is measured across the resistor, the current is calculated from the voltage. However I need to do this as accurately as I can, and as I understand the input impedance of the measurement device will distort my results greatly because it is close to the resistor's value. Instead of a voltmeter I'm using an oscilloscope (1M input impedance, 10x attenuation probe). My questions:
- How would one compensate the change in measured voltage due to the voltmeter input impedance?
- Is there any difference to doing this while using an oscilloscope?
If I'm doing something wrong here it would be nice to know as well. Any input is greatly appreciated!
EDIT: As I suspected, the way to go here is to consider the voltmeter/oscilloscope to be a resistor in parallel of the load to be measured - as Andy suggested. You should also check EM Fields' answer for measuring methods. HERE'S a well written paper about the effect of measurement device input impedance on your circuit.