ac / dc meters

[kenputer]

  I have some anolog panel meters that are marked ac volts in the 0 to 150 volt range. If I connect one to a 12 volt battery bank will they give me a true reading of dc volts or cause problems being ac connected to dc power.  Thanks

[K3CZ]

Kenputer:

The answer is:  They will probably work.  There are two types of AC meter movements: one rectifies the AC and applies the resulting DC signal to a DC meter movement that is specially calibrated for this, and the other (usually much older) is called a "moving coil" AC movement, and has no magnet, but results in a true "RMS"(heating value or DC equivalent) reading.  (the scale calibration is highly non linear) Either way, you need to check a midscale reading against a good DVM to see if there are any built-in miscalibrations.

                                                VAN   K3CZ   PE

[Nando]

If you have analog meters, without any connection ( boxes and resistors) then check the internal resistance of the meter that should give you the idea if one of them needs extra resistance to properly read the voltage at hand.

If you try to read voltages without the necessary additional resistance in series, then you may BLOW the meter or change the ACCURACY of it.

If it was designed for AC, some may have the rectifier internally or sometimes externally.

If you have a 1 milliamp meter, these may be used directly with a 0.050 ( 50 millivolts) current shunt to read the amps directly.

Like if you want to have a 50 amps shunt, connect the terminals of the meter to the SHUNT output terminals and if a 1 ma (0.050) meter the 100 % display will show 50 amps.

The same if you have a 10 ma with (0.050) range, the meter will read the 50 amps at full 100 % display.

The error due to the 10 ma meter with a 50 amps shunt will be so small that there is not need to worry about.

I hope this helps --

Regards

Nando