Technical Note: An Instrumented Pully for Field Measurements of Torque and Power

Abstract

An instrumented pulley was developed to overcome field problems associated with the conventional method of torque and power measurement. The prototype pulley was machined from mild steel, with stokes serving as strain beams. Strain gages in bridge arrangement attached to the spokes sense the bending stress due to the torque and convert this into millivolt output. Calibration results showed the torque-millivolt relationship was linear, hysteresis and error were less than 1% fs.

For power measurements, an additional tachometer with dc voltage output is necessary. With the tachometer, error in power measurement was +-1.03 W or .2% fs. Field tests showed its advantages over the calibrated motor such as, ease of installation, no weight addition relative to the original prime over, portability and safety.