DIFFERENTIAL IMPEDANCE TRANSDUCERS
In a differential impedance circuit, the coils of a pair of sensors form the opposite legs of a balanced bridge circuit. This differential configuration achieves its high resolution by eliminating any intervening summation and log amplifiers that would normally add noise and drift to the system. Additionally, by using electrically matched sensors on opposing legs of the same bridge, temperature effects common to the sensors and cabling of a differential sensor pair tend to be cancelled. This is true for the mechanical aspects of the sensor/target system also.
Kaman's KD-5100 and DIT-5200 products use differential impedance circuits for high resolution and low thermal sensitivity.