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
As has been mentioned a few times on this thread and others I think we must all appreciate that digital meters have a downside. There is a tendency to believe the resolution to cause accuracy whereas the old anologue meters we knew we were guessing the reading on the scale using line of sight with paralax errors. Whilst digital meters give more positive results i.e. an actual reading we should not take that reading as gospel. On DC they are quite good but a reading of 1.0000V is 1.0000 my-meter-volts and NOT 1.0000 absolute volts. If I use that meter to compare different voltages but over a close range then it might well be quite accurate as a comparitor, say 0.5V to 1.5V for instance or 0 to 2v or whatever as a comparison. AC is something different though and even clever meters sampling can be fooled to some extent. In the bad old days of my youth just about all the meters were anologue and if dropped or banged there was a price to be paid in future readings, You interpret the needle flicker to some extent and that probably gives you more of an inkling as to what is going on. A digital meter with a bargraph display perhaps is a midway to some extent.
I might have a digital watch that shows it is 12:36 and 18.23716 seconds but then again I set it two and a half minutes slow and it loses 5 to 10 seconds each day.
If we treat 90% of digital meters as just good guesses like the old anologue ones then we are on the road to enlightenment methinks.
As has been mentioned a few times on this thread and others I think we must all appreciate that digital meters have a downside. There is a tendency to believe the resolution to cause accuracy whereas the old anologue meters we knew we were guessing the reading on the scale using line of sight with paralax errors. Whilst digital meters give more positive results i.e. an actual reading we should not take that reading as gospel. On DC they are quite good but a reading of 1.0000V is 1.0000 my-meter-volts and NOT 1.0000 absolute volts. If I use that meter to compare different voltages but over a close range then it might well be quite accurate as a comparitor, say 0.5V to 1.5V for instance or 0 to 2v or whatever as a comparison. AC is something different though and even clever meters sampling can be fooled to some extent. In the bad old days of my youth just about all the meters were anologue and if dropped or banged there was a price to be paid in future readings, You interpret the needle flicker to some extent and that probably gives you more of an inkling as to what is going on. A digital meter with a bargraph display perhaps is a midway to some extent.
I might have a digital watch that shows it is 12:36 and 18.23716 seconds but then again I set it two and a half minutes slow and it loses 5 to 10 seconds each day.
If we treat 90% of digital meters as just good guesses like the old anologue ones then we are on the road to enlightenment methinks.
