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
From a popular well known multifunction installation tester accuracy specification for voltage measurement in the range 10 to 600 Volts:
±3% ± 1 V ±2 digits
Assuming a three digit display, a true value of say 230 Volts could be displayed as between 220 and 240 ie 4.3% potential error
Assuming a three digit display, a true value of say 55 Volts could be displayed as between 50 and 60 ie 10% potential error
I don't know if it has a 4 digit display but you get the idea!
Some accuracy specification has the initial +- % as a function of the range selected so using the same 3% as before, you could have an 18 Volt error plus 1 plus 2, ie 21 volts on any applied voltage..............
From a popular well known multifunction installation tester accuracy specification for voltage measurement in the range 10 to 600 Volts:
±3% ± 1 V ±2 digits
Assuming a three digit display, a true value of say 230 Volts could be displayed as between 220 and 240 ie 4.3% potential error
Assuming a three digit display, a true value of say 55 Volts could be displayed as between 50 and 60 ie 10% potential error
I don't know if it has a 4 digit display but you get the idea!
Some accuracy specification has the initial +- % as a function of the range selected so using the same 3% as before, you could have an 18 Volt error plus 1 plus 2, ie 21 volts on any applied voltage..............
