Development of a strain sensor using an oscillator circuit

A new type of strain sensor using a CMOS inverter oscillator circuit has been developed. This sensor does not require an amplifier because a counting device measures the frequency changes in the circuit voltage output caused by the resistance changes in the strain gauge. The characteristics and measurement accuracy of the sensor that consists of an oscillator circuit and a strain gauge are confirmed by static tensile tests of specimens. The test results reveal that the same level of accuracy as that of a conventional sensor is achieved by using a simple compensation factor assuming the existence of an internal resistance on the circuit.