Principle of Operation - Force Sensor

How do the PASCO force sensors work?

The PASCO force sensors employ four strain gauges epoxied to a binocular dual-beam made from annealed aluminum. The strain gauges are wired to form a full-bridge circuit that is driven by a constant voltage source. The voltage across the bridge circuit is proportional to the applied force.

A strain gauge is a resistor that changes its resistance when it is stretched or compressed. Since it is a resistor that has current passing through it, it will generate heat that will be transferred to the beam of the load cell. Though the strain gauge is designed to minimize the effects of thermal expansion, the transfer of heat to the load beam will cause the sensor to drift due to the expansion of the metal below the strain gauge. This drift can be reduced by storing the sensor at room temperature and by allowing the sensor to "warm up" for at least four minutes prior to use to make sure that any drift due to thermal expansion can be removed by taring or zeroing the sensor.