The new current loop: an instrumentation and measurement circuit topology

A new current loop analog measurement circuit topology is presented that significantly outperforms the classic Wheatstone bridge in many instrumentation, measurement, and control applications. Using active subtraction as the key enabling technology, the new current loop can provide greater accuracy with less excitation power and fewer connecting wires. Several sensor elements can exist in the same current loop with their independent and combined outputs available simultaneously. Measurement functions beyond what an equivalent Wheatstone bridge can provide have been accomplished. The limitations of the Wheatstone bridge are recalled and the new current loop theory is presented along with test data acquired using an elementary single component active subtractor