“Industrial torque meters cost a lot ($4500). I’ll show you how to build a low buck version with an Arduino. Why? Because I want to test power tools to see if the actual specs live up to the marketing specs. The reason this works is Load Cells are cheap on-line. They work by measuring the deflection in an aluminum beam. Normally that deflection is detected by an electrical device called a Wheatstone Bridge. When the Wheatstone Bridge stretches or contracts it changes the resistance, which is then read by a micro-controller.”