I recently purchased 2 little voltmeters they look like the sort that would go in a control or instrument panel they are connected with just 2 wires which provide the operating supply ( they light up green and red) however the green one states it will work between 20and 500 volts and the red one between 60 and 480 volts. When they are both on the green one indicates normally around 241 volts the red one shows 235 volts why the discrepancy I know it's not much but makes you wonder if one of them is lying. Secondly I've noticed that the green one tracks voltage changes faster than the red one and that a few times the green one jumps down to 238 then up to 241 multiple times while the red one stays the same and I think can see a slight flicker in my filament lamps when this is happening incidentally both meters are connected to the same plug a 2 pin 5 amp one
The question of why you need to measure the voltage has not been answered.
Are you worried that the peaks will to high resulting in equipment damage?
Are you concerned that the mains supply at the intake regularly exceeds or drops below the prescribed limits?
Or are you concerned that equipment within your installation is causing issues either causing excessive voltage drops or do you have solar PV possibly pushing the voltage up?
Until you have determined what you want to measure and why you cannot select the tester you need to use.
Hi again the reason for my original question was because I bought 2 voltmeters that gave slightly different readings from the same source and I just wanted to know why which I now do so in a way I've got my answer and I think my next move will be to try to get a true RMS meter which will happen soon I hope. The next point is that I wanted to find out how is that he 3rd harmonic current able to flow the opposite way to the main current i think I sort of understand now is it in the same way as other much higher frequencys travel back up the supply wiring? As I understand it these multiples of 50 cycles can go up to 500 odd Kilocylcles I hope I'm some where near to being right
Okay, I’m just thinking that you will end up with several volt meters all displaying a different voltage and none of them may actually be wrong, just displaying different voltages at different points on the cycle.
When I can get my paws on a second hand dimmer I will do the test I do have motor speed controller but it's for 110 volts only so not really sure if it will do its very old built by some apprentice at our local nuclear powerstation
