Basic Introduction to Torque Sensors

The torque commonly referred to is the external torque, such as the rotation of the machine tool spindle being the result of the external torque provided by the power source, while the torque is the internal torque. When the spindle is working, the reaction of the cutting force of the tool on the spindle causes torsional elastic deformation, which can be used to measure the magnitude of the torque. Torque is the torque that causes an object to undergo rotational or torsional deformation, equal to the product of force and arm of force.
Torque is the most frequently involved parameter in a rotating power system. In order to detect rotational torque, a torque angle phase difference sensor is commonly used. The sensor is equipped with two sets of gears with identical tooth numbers, shapes, and installation angles at both ends of the elastic shaft, and one proximity (magnetic or optical) sensor is installed on the outer side of each gear. When the elastic axis rotates, these two sets of sensors can measure two sets of pulse waves. By comparing the phase difference between the front and rear edges of these two sets of pulse waves, the amount of torque borne by the elastic axis can be calculated. The advantages of this method are that it achieves non-contact transmission of torque signals, and the detection signal is a digital signal; Disadvantages: Large volume, difficult to install, and low speed performance is not ideal due to the slow front and rear edges of the pulse wave being difficult to compare at low speeds.
The manufacturer of torque sensors has learned that the mature testing method for torque testing is strain electrical testing technology, which has advantages such as high accuracy, fast frequency response, good reliability, and long service life. Paste the special torsion strain gauge on the elastic shaft to be measured with strain adhesive and form a strain bridge. If the strain bridge is provided with working power, the electrical signal of the elastic shaft under torsion can be tested. This is the basic torque sensor mode. However, in a rotating power transmission system, the most challenging problem is how to reliably transmit the bridge pressure input and detected strain signal output of the strain bridge on the rotating body between the rotating and stationary parts, usually achieved using conductive slip rings. Due to the fact that the conductive slip ring belongs to frictional contact, there is inevitably wear and heat generation, which limits the rotational speed of the rotating shaft and the service life of the conductive slip ring. And due to unreliable contact, signal fluctuations can result in large measurement errors or even unsuccessful measurements. In order to overcome the defects of conductive slip rings, another method is to use radio telemetry: amplify the torque strain signal on the rotating axis and convert it into a frequency signal through V/F conversion. Through carrier modulation, transmit it from the rotating axis to the outside of the axis through radio transmission, and then receive it without wires to obtain the signal of the rotating axis being twisted. The energy supply on the rotating shaft is a battery fixed on the rotating shaft. This method is called telemetry torque meter.