Correct, so we used a high impedance voltage meter across a calibrated resistor in series with the circuit under test. It was 7 years ago I did the work and now

Correct, so we used a high impedance voltage meter across a calibrated resistor in series with the circuit under test. It was 7 years ago I did the work and now rarely work hands on with electronics so I am hazy on the exact details but it’s all in the published journal paper, which, as always with science papers is now behind a paywall. UPDATE: I miss remembered, we used the high impedance electrometer to buffer the input of a National Instruments interface board so we could record the voltage build up across the storage capacitors, if you use a normal voltmeter the caps just discarge into the voltmeter and the charge never builds up enough to allow the micro controller to turn on, run the code it needs to and then go back to sleep. You land up with some really nice sawtooth wave forms with this method and, as the acceleration on the vibrational energy harvester increases, the frequency of the sawtooth changes proportionally up to a point where the system is transmitting all the time.