Views showing the interior and the instructions on the rear for extending the range of the meter.
Ex WW2 German ohmmeter 5 ranges from 1 ohm to 10 Mohm which
had been taken apart and the meter section had been converted into a
0-120 uA (0-120mV) meter. The resistance selection had lost two knobs but otherwise was complete. The original scale had
been removed and replaced with a hand calibrated one (dated 9/12/49).
I have married the two parts together and after some experimentation have discovered how it may have been intended to work. I have now made a new scale for the four lower ranges and fitted two replacement knobs. The unit takes two 1.5 volt cells which no longer seem to be available, they are shorter and larger diameter than AA cells.
In use the unknown resistance is connected to the black terminals and the left hand knob is turned clockwise until the pointer reaches the calibration point, the right hand button is then depressed and the reading multiplied by the appropriate constant as shown in the table gives the resistance.
This is what I think is the circuit.
Do you know anything about this instrument or can you point me in the right direction for a circuit diagram and more importantly a picture of the original scale markings?