Mutual inductance bridge for low-temperature thermometry and susceptibility measurements

Abstract

We describe a solid-state mutual inductance bridge suitable for low-temperature thermometry and susceptibility measurements. The design features an electronically simulated variable mutual inductance. Particular care is taken to reduce spurious capacitive effects. The bridge is highly stable and linear. It has a resolution of 10(-4) over the range 15 microH to 150 mH, and a noise limited sensitivity of 55 I(p) (-1) nH with a l-s time constant, where I(p) is the rms primary current in mA. Application to thermometry is discussed.