What is a Torque Sensor?

What is a Torque Sensor?

A torque sensor is a device used to detect the torque on various rotating or non-rotating mechanical parts. It converts the physical changes in torque into precise electrical signals. Torque sensors can be applied in manufacturing viscometers, electric (pneumatic, hydraulic) torque wrenches, and more, offering high accuracy, fast response, good reliability, and long lifespan.

Types of Torque Sensors

Torque sensors are classified into dynamic and static categories. Dynamic torque sensors can also be referred to as torque sensors, torque speed sensors, non-contact torque sensors, rotary torque sensors, etc.

Dynamic Torque Sensors

Dynamic torque sensors are often used in rotating power systems. To detect rotational torque, torsional angle phase difference sensors are commonly used. These sensors install two sets of gears with the same number of teeth, shape, and installation angle on both ends of an elastic shaft, and proximity (magnetic or optical) sensors are mounted outside these gears. When the elastic shaft rotates, these two sets of sensors measure two sets of pulse waves. By comparing the phase difference between these pulse waves, the torque on the elastic shaft can be calculated.

Advantages:

- Non-contact transmission of torque signals.

- Digital detection signals.

Disadvantages:

- Large size.

- Difficult to install.

- Poor performance at low speeds due to slow pulse wave edges.

Strain Gauge Technology

A mature method for torque testing is strain gauge technology. This method features high accuracy, fast response, good stability, and long lifespan. A special torsion strain gauge is adhered to the elastic shaft to be measured, forming a strain bridge. By supplying power to the strain bridge, the torsional electrical signal of the elastic shaft can be measured, which is the default mode for torque sensors.

However, in rotating power transmission systems, the challenge lies in how to reliably transmit the power input to and the detected signal output from the rotating part to the stationary part. A common method is using conductive slip rings.

Conductive Slip Rings

Conductive slip rings involve frictional contact, which inevitably leads to wear and heat, limiting the rotational speed and lifespan of the slip rings. Moreover, unreliable contact can cause signal fluctuations, leading to measurement errors or failures.

Wireless Telemetry Method

To overcome the drawbacks of conductive slip rings, a wireless telemetry method can be used. In this approach, the torque deformation signal on the rotating shaft is amplified and converted to a frequency signal (V/F conversion). This signal is then wirelessly transmitted using carrier modulation methods from the rotating shaft to the outside. The torsional signal of the rotating shaft is received using a radio receiver. The energy supply for the rotating shaft is provided by batteries fixed on the rotating shaft. This method is known as a telemetry torque meter.