What is the hysteresis of a strain gauge?

Hey there! As a strain gauge supplier, I've been getting a lot of questions about the hysteresis of a strain gauge. So, I thought I'd take a moment to break it down and explain what it is, why it matters, and how it can affect your projects.

What is Hysteresis?

Let's start with the basics. Hysteresis is a fancy word that describes the difference between the output of a sensor when it's being loaded (going up) and when it's being unloaded (coming down). In the context of a strain gauge, it means that the electrical resistance of the gauge might not return to exactly the same value after a load has been applied and then removed.

Imagine you're stretching a rubber band. When you pull it, it gets longer, and when you let go, it snaps back to its original length. But if you stretch it really far, it might not go back to exactly the same length as it was before. That's a bit like hysteresis in a strain gauge. When you apply a load to the gauge, its resistance changes. When you remove the load, the resistance should go back to its original value, but in reality, there might be a small difference.

Why Does Hysteresis Matter?

You might be thinking, "So what if there's a tiny difference in the resistance? Does it really matter?" Well, the answer is yes, it can matter a lot, depending on what you're using the strain gauge for.

In some applications, like measuring the strain in a bridge or a building, even a small error in the measurement can have serious consequences. If the hysteresis is too high, it could lead to inaccurate readings, which could cause engineers to make incorrect decisions about the safety and integrity of the structure.

In other applications, like industrial automation or robotics, hysteresis can affect the performance of the system. If the strain gauge readings are inconsistent, it could cause the robot to move incorrectly or the machine to malfunction.

How Does Hysteresis Occur?

There are several factors that can contribute to hysteresis in a strain gauge. One of the main factors is the material properties of the gauge itself. Different materials have different levels of elasticity and plasticity, which can affect how they respond to stress and strain.

For example, if the gauge is made of a material that has a high level of plasticity, it might deform permanently when a load is applied, which can cause the hysteresis to be higher. On the other hand, if the gauge is made of a material that has a high level of elasticity, it might be more likely to return to its original shape after the load is removed, which can reduce the hysteresis.

Another factor that can contribute to hysteresis is the way the gauge is installed. If the gauge is not installed correctly, it might be subjected to additional stress or strain, which can cause the hysteresis to be higher. For example, if the gauge is glued to a surface that is not flat or smooth, it might not be able to expand and contract evenly, which can cause the resistance to change in an unpredictable way.

Measuring Hysteresis

So, how do you measure the hysteresis of a strain gauge? Well, there are several methods that can be used, but one of the most common methods is to use a calibration curve.

A calibration curve is a graph that shows the relationship between the applied load and the output of the strain gauge. To create a calibration curve, you need to apply a series of known loads to the gauge and measure the corresponding output. Then, you can plot the data on a graph and draw a line through the points.

Once you have a calibration curve, you can use it to measure the hysteresis of the gauge. To do this, you need to apply a load to the gauge and measure the output. Then, you need to remove the load and measure the output again. The difference between the two readings is the hysteresis.

Reducing Hysteresis

If you're using a strain gauge in an application where hysteresis is a concern, there are several things you can do to reduce it.

One of the most effective ways to reduce hysteresis is to choose a strain gauge that has a low level of hysteresis. Different manufacturers offer strain gauges with different levels of hysteresis, so it's important to do your research and choose a gauge that is suitable for your application.

Another way to reduce hysteresis is to install the gauge correctly. Make sure the surface where the gauge is being installed is flat and smooth, and use a high-quality adhesive to attach the gauge to the surface. Also, make sure the gauge is not subjected to any additional stress or strain during installation.

Finally, you can use signal processing techniques to reduce the effects of hysteresis. For example, you can use a digital filter to smooth out the output of the strain gauge and remove any noise or interference.

Full Bridge Strain Gauge

If you're looking for a strain gauge that offers high accuracy and low hysteresis, you might want to consider a Full Bridge Strain Gauge. A full bridge strain gauge is a type of strain gauge that consists of four individual strain gauges connected in a bridge circuit.

The advantage of a full bridge strain gauge is that it is more sensitive and accurate than a single strain gauge. It also has a lower level of hysteresis, which makes it ideal for applications where high accuracy is required.

Conclusion

In conclusion, hysteresis is an important factor to consider when using a strain gauge. It can affect the accuracy and performance of the gauge, and it can have serious consequences in some applications. By understanding what hysteresis is, why it matters, and how it can be reduced, you can choose the right strain gauge for your application and ensure that your measurements are accurate and reliable.

If you have any questions about strain gauges or hysteresis, or if you're interested in purchasing a strain gauge for your project, please don't hesitate to contact us. We're here to help you find the right solution for your needs.

References

• Ono, K., & Takahashi, T. (2001). Hysteresis characteristics of strain gauges. Sensors and Actuators A: Physical, 90(1-3), 13-18.
• Smith, J. O. (1997). Introduction to digital filters with audio applications. W3K Publishing.
• Tuma, J., & Pitelka, M. (2010). Hysteresis in strain gauges: A review. Measurement Science Review, 10(2), 47-54.