Self-Balancing Conductance Bridge for Low Temperature Thermometry

A self-balancing conductance bridge is described that operates at sufficiently low power levels to be useful for thermometry at very low temperatures. It uses a four-terminal configuration which largely eliminates the effect of lead resistance. Operation at a low frequency, synchronized with the 60 Hz power frequency, and the use of a wide dynamic range error detector make the bridge very insensitive to hum pickup and capacitive unbalance.