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
Hi ebee and mhrestorations I totally agree I did think that being digital and brand new still in there little plastic bags my meters would of been spot on what first concerned me was the fact that they both showed different voltages this being in spite of the fact they were connected to the same plug if the difference had been say 1 volt between them then I wouldn't have worried but it was six volts which as I said made me think one of them was being les than truthful. But after all the replies I've had I get that it's just a mix of how the meters were set up and reading errors caused by sample rate and frequency as well as harmonics on the mains so if one reads say 241 and the other 236 then il accept that the voltage is around 240 even more so if other meters show around the same figure that will do. Ide forgotten that the voltage flickers a bit I haven't used an analogue meter in so long it had gone from my mind. Regarding mains waveform that's how mine looked flattened out tops or crests I did wonder if it was a funny on my scope so I coupled up a signal generator and that gave a perfect sine wave so it really was the mains crests being crushed when I say crests of course it applies equally to both halves of the sine wave what do you call a negative going crest??
Hi ebee and mhrestorations I totally agree I did think that being digital and brand new still in there little plastic bags my meters would of been spot on what first concerned me was the fact that they both showed different voltages this being in spite of the fact they were connected to the same plug if the difference had been say 1 volt between them then I wouldn't have worried but it was six volts which as I said made me think one of them was being les than truthful. But after all the replies I've had I get that it's just a mix of how the meters were set up and reading errors caused by sample rate and frequency as well as harmonics on the mains so if one reads say 241 and the other 236 then il accept that the voltage is around 240 even more so if other meters show around the same figure that will do. Ide forgotten that the voltage flickers a bit I haven't used an analogue meter in so long it had gone from my mind. Regarding mains waveform that's how mine looked flattened out tops or crests I did wonder if it was a funny on my scope so I coupled up a signal generator and that gave a perfect sine wave so it really was the mains crests being crushed when I say crests of course it applies equally to both halves of the sine wave what do you call a negative going crest??
