A new high-speed recording potentiometer

FAST SELF-BALANCING POTENTIOMETERS were improved vastly during the war for the rapid recording of thermocouple voltages. In certain of these, the direct current of the thermocouple is converted by mechanical oscillators to alternating current, and amplified to drive the balancing motor. These give good vibrationproof performance, but because their input circuit is connected directly to the power amplifier through the converter one must take care to shield the input against electromagnetic pickup such as results from operation of switches, and must avoid grounding both the instrument and thermocouple, because multiple grounds can introduce currents which are converted and amplified to cause large errors in the record.