Battery operated torque wrench with digital display

摘要

A battery operated torque wrench having a digital display to give a numerical representation of torque applied to a rotational workpiece, such as a socket head bolt. Applied torque is sensed by variable resistors responsive to mechanical strain in a flexure element in the head of the wrench. The variable resistors are connected in a bridge circuit which yields an electrical analog signal when the bridge is unbalanced due to mechanical strain in the variable resistors. The electrical analog signal is tracked and converted into a digital equivalent by a servo-type feedback circuit. Each iteration of the feedback circuit generates a counting pulse which is registered on a set of binary coded decimal (BCD) counters connected in cascade. The outputs of the BCD counters are displayed on light emitting diode displays on the wrench handle. Overrange, underrange, and low power indicator means and power strobing means are also disclosed.