NASA's Anderson Loop

The Anderson loop is a simply implemented measurement circuit topology that uses active subtraction instead of the passive subtraction accomplished by the classic Wheatstone bridge. Larger, inherently linear signals from sensing-element impedance change are available with less excitation power and without the use of transmitters to achieve immunity to wire-resistance variations. Transducers can be designed with any convenient quantity of sensor elements. Transducer intelligence can be implemented within the signal conditioner. The change in a single sensing element can be used in several simultaneous measurements. Sensor elements can appear to have any desired impedance level and influence on any of several outputs.