QTK compensator

This ancient-looking device was manufactured in the 1950s by Metra Blansko. Before the advent of precise electronic amplifiers, it was very difficult to measure weak voltages. That was the purpose of this instrument. The operator would adjust the voltage divider until the current passing through the galvanometer would be zero. Then, the output voltage of the divider would be equal to the measured voltage. The actual value of the voltage had to be calculated. Today's digital multimeters can show the value directly.