How Does a Torque Sensor Work?

To understand how torque sensors work let us first explain what a torque sensor is. A torque sensor, also known as a torque transducer or torque meter, is a device that measures the torque applied to an object.

It is commonly used in a variety of industrial applications, such as automotive testing, robotics, and manufacturing. A good e-bike will also be using a torque sensor to measure how hard you push the pedals. Combined with a cadence (or even absolute angle) sensor it sends inputs to the motor controller algorithm that in turn controls how much assistance the motor provides.

There are several different types of torque sensors, but one of the most common is the strain gauge torque sensor. This type of sensor consists of a shaft, a disc, or a shaft with a torsion bar attached to it. When torque is applied the material (often metal) twists or bends slightly, causing a change in its length and/or shape where one or more strain gauges are applied. This change in shape causes a corresponding change in the electrical resistance of the strain gauge.

The strain gauge is connected to a Wheatstone bridge circuit, which measures the change in resistance and converts it into an electrical signal. This signal is then amplified and processed to provide a torque reading. The output signal can be analog or digital, depending on the type of sensor.

Other types of torque sensors use different principles, such as magnetic or optical sensing, but they all rely on measuring the deformation caused by the applied torque in some way.

A number of other torque sensor technologies exist, and you can read more about how these torque sensors work in our technology comparison.