The aim of this experiment is to confirm the error between the real voltage and the reading of a DC voltmeter with signals of different waveforms, and most important how to obtain the real measurement. This is important, because when we read the hv voltage that we supply to our hv devices, the hv probe is not the only device which introduces errors. One has to consider whether the DC signal being measured is pure dc or any type of pulsed dc.
Equipment used
Signal generator set at 1 V peak dc @ 20 kHz
Oscilloscope set at 0.1 V/div
Standard (not True RMS type) Multimeter
Setup
The signal generator is set at 1 V peak output, and at a frequency of 20 khz. The output from the signal generator is fed to an oscilloscope in parallel with a multimeter, in parallel with a 10 kOhm resistive load. Various waveforms are then selected to check the results on both oscilloscope and multimeter.
Pulsed sine wave testing
This is the kind of waveform one would normally get from a monitor's hv output at 20 khz. As you can see, at 1 V peak signal (as shown on the oscilloscope), the multimeter shows 0.226 V. If this was a reading from a hv probe, one would read 22 kV, when the actual peaks reach 100 kV! Of course this reading varies according to the multimeter frequency response, and duty cycle of the signal.
Pulsed square wave testing
This time, a square wave of 20 kHz, 1 V peak is fed to both meter and oscilloscope in parallel. As you can see, at 1 V peak signal (as shown on the oscilloscope), the multimeter shows 0.436 V. If this was a reading from a hv probe, one would read 43.6 kV, when the actual peaks reach 100 kV!
Pulsed triangular wave testing
This time a triangular dc waveform at 20 kHz, 1 V peak is fed to the instruments. At 1 V peak signal (as shown on the oscilloscope), the multimeter shows 0.193 V. If this was a reading from a hv probe, one would read 19 kV, when the actual peaks reach 100 kV!
Conclusions
