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
. . . I understand that GPS can measure altitude. . . .
It does, regardless of the system you are using - NAVSTAR (America), GLONASS (Russia), Galileo (Europe) and BeiDou (China). GPS Speed is calculated as a time between two points, which are assumed to be a straight line. This will give an error if you are not travelling in a straight line.
NAVSTAR.was the original system and was developed by the US Airforce. It broadcast two signals, one coded for use by the US military, which was accurate, and a second one for use by everyone else, which incorporated a random error, which is where you probably got your error from. President Reagan signed an order in 2000 that removed the random error, however it could be reapplied if required for “defence purposes”.
. . . I understand that GPS can measure altitude. . . .
It does, regardless of the system you are using - NAVSTAR (America), GLONASS (Russia), Galileo (Europe) and BeiDou (China). GPS Speed is calculated as a time between two points, which are assumed to be a straight line. This will give an error if you are not travelling in a straight line.
NAVSTAR.was the original system and was developed by the US Airforce. It broadcast two signals, one coded for use by the US military, which was accurate, and a second one for use by everyone else, which incorporated a random error, which is where you probably got your error from. President Reagan signed an order in 2000 that removed the random error, however it could be reapplied if required for “defence purposes”.
