Volume 34, Issue 6 (November 2011)
Local Displacement Transducer With Anderson Loop
Wheatstone bridge has long been used in many strain-gauge based measuring instruments including the local displacement transducer. In this paper, an alternative circuit to the Wheatstone bridge, Anderson loop, for local displacement transducers is examined. Local displacement transducers were manufactured in an identical fashion but with different circuitries. In both circuitries, similar gain and filter were applied to the output signals. An identical experimental setup for both Anderson loop and Wheatstone bridge local displacement transducers was used in the evaluation, and, therefore, any differences in performances of the local displacement transducers are attributed to the circuitry. The range of displacement examined for the local displacement transducer was 0.4 mm. Self-heating of the strain gauges was found to occur regardless of the circuitry used when a high input current was used in the local displacement transducer with Anderson loop or a high input voltage was used in the local displacement transducer with Wheatstone bridge. The effects of self-heating of strain gauges are only evident in long duration tests. The local displacement transducer with Anderson loop was found to be twice as sensitive as that with Wheatstone bridge for similar input current. Furthermore, the local displacement transducer with Anderson loop outperformed the local displacement transducer with Wheatstone bridge in terms of lower deviation, hysteresis and repeatability errors.