Wireless torque measurement systems are previously studied in [1], [2] and [3]. Some of these systems use
strain gauges, which have to be glued on the shaft of an electric motor under test [1], [2]. Problem with glued
strain gauges is that they are very hard to orient precisely, especially in the field conditions. Their
mechanical reliability is also questionable. Some wireless systems have their weakness in wireless
communication [3], and even analog radio communication techniques have been adopted [4]. These radio
techniques are not robust, especially in noisy environment such as heavy machinery. The wireless torque
measurement system described in this paper utilizes stain gauge collar, where strain gauges are aligned
precisely by assembly of collar around a shaft. Moreover, the strain gauge elements are covered by collar,
thus protected from the external stress.