Multigen M820/M830 are 96x96mm cased three phase generator monitoring meters.
The M820 measures Volts, Amps, Frequency, Active Power, Apparent Power, Engine Oil Pressure, Engine Coolant Temperature, Hours Run, dc Volts and displays the values on a clear LCD. In addition to the above, it can be supplied with over-temperature and under-pressure relays.

See
M820 3X Registers
M820 4X Registers