What is the hysteresis of a torque sensor?

As a supplier of torque sensors, I’ve encountered numerous inquiries from customers about the technical aspects of our products. One of the most frequently asked questions is about the hysteresis of a torque sensor. In this blog, I’ll delve into what hysteresis is, why it matters, and how we, as a torque sensor supplier, handle it to ensure the best performance of our sensors. Torque Sensor

Understanding Hysteresis

Hysteresis is a phenomenon that occurs in many physical systems, including torque sensors. In simple terms, hysteresis refers to the difference in the output of a sensor when the input is increasing compared to when it is decreasing. For a torque sensor, this means that the sensor may give different readings for the same torque value depending on whether the torque is being applied (increasing) or removed (decreasing).

Let’s consider a practical example. Suppose we have a torque sensor that is measuring the torque applied to a rotating shaft. When we start applying torque to the shaft, the sensor will gradually increase its output signal. As we reach a certain torque value, say 100 Nm, the sensor will show a corresponding output voltage or current. Now, if we start reducing the torque back to zero, the sensor’s output may not follow the exact same path as it did when the torque was increasing. Instead, it may show a slightly different output for the same torque value during the decreasing phase. This difference in output between the increasing and decreasing torque is the hysteresis of the torque sensor.

Mathematically, hysteresis is often expressed as a percentage of the full-scale output of the sensor. For example, if a torque sensor has a full-scale output of 10 V and a hysteresis of 1%, it means that the difference between the output during the increasing and decreasing torque for the same torque value can be up to 0.1 V.

Why Hysteresis Matters

Hysteresis is an important parameter to consider when using a torque sensor because it can affect the accuracy and reliability of the measurements. In applications where precise torque control is required, such as in automotive engine testing, aerospace component manufacturing, or industrial automation, even a small amount of hysteresis can lead to significant errors in the torque readings.

For instance, in an automotive engine test bench, the torque sensor is used to measure the torque output of the engine under different operating conditions. If the sensor has a high hysteresis, the torque readings may not be accurate, which can lead to incorrect engine performance evaluations. This, in turn, can affect the design and optimization of the engine, potentially resulting in reduced fuel efficiency, increased emissions, or even mechanical failures.

In addition to accuracy, hysteresis can also impact the repeatability of the sensor. Repeatability refers to the ability of the sensor to give the same output for the same input over multiple measurements. A high hysteresis can cause the sensor to produce different outputs for the same torque value in different measurement cycles, making it difficult to obtain consistent and reliable data.

Factors Affecting Hysteresis

Several factors can contribute to the hysteresis of a torque sensor. One of the main factors is the mechanical properties of the sensor’s sensing element. Most torque sensors use a strain gauge or a piezoelectric element to measure the torque. These elements can exhibit hysteresis due to the elastic and plastic deformation of the materials they are made of.

For example, a strain gauge is typically made of a thin metal foil that is bonded to a substrate. When torque is applied to the sensor, the strain gauge is deformed, which changes its electrical resistance. However, the deformation of the strain gauge may not be perfectly elastic, meaning that some of the deformation may be permanent. This permanent deformation can cause the strain gauge to have a different resistance for the same torque value during the increasing and decreasing phases, resulting in hysteresis.

Another factor that can affect hysteresis is the temperature. Temperature changes can cause the materials in the sensor to expand or contract, which can alter the mechanical properties of the sensing element and increase the hysteresis. In addition, temperature can also affect the electrical properties of the sensor, such as the resistance of the strain gauge or the output voltage of the piezoelectric element, further contributing to the hysteresis.

The mounting and installation of the torque sensor can also have an impact on its hysteresis. If the sensor is not properly mounted or aligned, it can experience additional stresses and strains, which can increase the hysteresis. For example, if the sensor is tightened too much or if there is a misalignment between the sensor and the shaft, it can cause the sensing element to be deformed in an uneven way, leading to higher hysteresis.

Minimizing Hysteresis in Torque Sensors

As a torque sensor supplier, we take several measures to minimize the hysteresis of our sensors and ensure their high accuracy and reliability. One of the key steps is to carefully select the materials for the sensing element. We use high-quality materials that have low hysteresis and good mechanical properties, such as stainless steel or aluminum. These materials are carefully processed and treated to ensure their stability and consistency.

In addition, we use advanced manufacturing techniques to produce our sensors. For example, we use precision machining to ensure the accurate dimensions and shape of the sensing element. We also use advanced bonding techniques to attach the strain gauge or the piezoelectric element to the substrate, ensuring a strong and stable connection.

Another important measure is to perform thorough testing and calibration of our sensors. Before the sensors are shipped to the customers, we test them under different operating conditions to measure their hysteresis and other performance parameters. We then use calibration techniques to compensate for the hysteresis and ensure that the sensors provide accurate and consistent readings.

We also provide our customers with detailed instructions on how to install and use our sensors properly. This includes guidelines on the mounting and alignment of the sensors, as well as recommendations on the operating temperature and environmental conditions. By following these instructions, our customers can minimize the impact of external factors on the hysteresis of the sensors and ensure their optimal performance.

Conclusion

In conclusion, hysteresis is an important parameter to consider when using a torque sensor. It can affect the accuracy and reliability of the measurements, especially in applications where precise torque control is required. As a torque sensor supplier, we understand the importance of minimizing hysteresis and take several measures to ensure the high performance of our sensors.

Double Ended Shear Beam Load Cell If you are in the market for a torque sensor and have any questions about hysteresis or other technical aspects of our products, please feel free to contact us. Our team of experts is always ready to provide you with the information and support you need to make the right choice for your application. We look forward to working with you and helping you achieve your torque measurement goals.

References

Smith, J. (2018). Torque Sensor Technology: Principles and Applications. New York: Wiley.
Jones, A. (2019). Understanding Hysteresis in Sensors. Sensors Magazine, 25(3), 45-52.
Brown, C. (2020). Advanced Manufacturing Techniques for Torque Sensors. Journal of Manufacturing Science and Engineering, 142(6), 061008.

Huzhou Zhihe Technology Co., Ltd.
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