1. Introduction

The SMA torque wrench is a necessary tool to protect instrument joints.  When fastening the SMA connectors, the purpose of using a SMA torque wrench is to control the applied force to ensure that the joint thread is not damaged by excessive torque but fastened firmly. Firstly, set an upper limit of the torque required. When the torque applied reaches this value, the wrench will make a "cada" sound or get the wrench joint bent a little. It indicates that the wrench has been tightened and no more force is needed.

2.Working principle

(1) The torque wrench in the "cada" sound is prompted that you have reached the required torque value;

(2) The sound "cada" issued by the torque wrench is generated by the internal torque releasing structure, which is composed of pressure spring, torque releasing joint and torque ejector rod.

(3) First, set the required torque value on the torque wrench (the spring covers the rod and puts pressure on the torque release joint), lock the torque wrench and start tightening the bolt. When the bolt reaches the torque value (when the torque is greater than the spring pressure), there will be a momentary disjointed effect. The "cada" sound of the metal casing of the spanner is produced at the instant of the disjointed effect. This is to confirm the torque value of the reminder function.