A 3-wire differential resistance measurement circuit

The authors describe two circuit techniques to measure small differences between two resistors or small changes in a transducer resistance. The resistances of the three connecting wires to the transducer are canceled by methods other than the conventional 3-lead circuits. The first method uses a pair of matched current sources. The second employs a dual-slope analog-to-digital converter with a multiplexed preamplifier. Based on the latter method, a 3 1/2-digit, 0.1 /spl deg/C resolution, 3-lead platinum thermometer was built successfully.<>