Triometer "System Abrahamsohn"

DC multimeter

Triometer "System Abrahamsohn" test meter in leatherette covered wooden case housing 4 shunts and one series resistor. Instructions (in German) are on the inside lid. This nice test meter can be used to measure volts, amps and (with an external battery) ohms by reference to the printed table in the lid. The basic moving coil meter with mirror scale has a 100mV 2mA movement. There are two pushbuttons (one originally missing) to alter the sensitivity. The shunts are ingenious, they can only be inserted one way into the two lower terminals and when inserted a switch is operated to alter the internal circuitry to enable the instrument to be used as an ammeter. Have a look at one of my other German meters. This model was first made made in 1931. Gossen started making the "Mavometer" in 1925 which offered much the same range of measurements using shunts and voltage multipliers.

This was given to me in 2004 by Bob Haslam whose father acquired it many years ago. I have now replaced the missing pushbutton, repaired the switch contacts and traced out the circuit diagram.