Strain gauges for data acquisition

- an overview or tutorial about strain gauges used to measure the strain of elements in a system, and often found in data acquisition systems.

Strain gauges are used in a variety of applications, including data acquisition, for measuring the strain or deformation of a mechanical element. Essentially a strain gauge is a resistive transducer that has an electrical output that is proportional to the amount it has been deformed under strain. If the strain gauge is attached to a mechanical element, then it will be deformed along with it and provide an output according to the strain that it undergoes.

Strain gauges are normally fairly simple in their concept. They may simply comprise of a thin resistive element, often foil, that may be mounted using an adhesive to the element under test. As it deforms, so does the strain gauge whose resistance changes, even if by a small amount, so that the change can be measured and converted to give an indication of the strain.

The basic strain gauge load cell can easily be used in such a way that it can be used to give an indication of pressure, force or tension in a network. As a result strain gauges are widely used in many areas of industry and the data may be captured using a data acquisition system.

What is strain?

In order to look at strain gauges in more detail, it is necessary to first take a look at what exactly strain is.

There are many definitions of strain that can be seen in literature of all sorts. In scientific and engineering applications strain is defined as the deformation caused by the action of stress (i.e. force per unit area on a given plane) on a body. Strain is therefore manifested by a change in shape and or size. Thus stress can be defined as the amount of deformation a material experiences per unit of original length in response to stress.

Practical implementation of strain gauges

It is found that the resistance changes on a strain gauge element are exceedingly small. As a result it is necessary to take account of this in the circuitry used to ensure that the greatest levels of accuracy can be obtained.

Although it is possible to detect the resistance changes on a strain gauge relatively easily with modern equipment, it is necessary to ensure that the measurements that are taken are as accurate as possible. It is also necessary to ensure that changes resulting from other environmental conditions such as temperature are compensated for. To achieve all of this, a technique that has been in use for many years is employed and a Wheatstone bridge circuit is used for each load cell.

The Wheatstone bridge circuit itself compromises four resistors. Other resistors are used to calibration resistors and temperature dependent elements are used to compensate and calibrate the bridge output signal. Thus each strain gauge cell has four wires: two for the input power, and two for the output signal.

By Ian Poole

<< Previous   |   Next >>

Share this page

Want more like this? Register for our newsletter

A medal for mobile medicine? Rudy Ramos | Mouser Electronics
A medal for mobile medicine?
Medical services the world over are coming under great pressure to deliver high-quality healthcare and, at the same time control costs. Alongside this, patients are becoming far more involved in their wellbeing as well as wanting a high standard of healthcare with even greater convenience than before. As people are more mobile these days, mobile healthcare (mHealth) avoids the need to visit the doctor’s office and allows patients to provide health data to providers, as well as receive care, anywhere on the planet.
Online - Fundamentals of Modern RF and Wireless Communications Engineering
This on-line course enables you to quickly get up-to-speed & understand key concepts of modern radio frequency, RF & wireless communications systems

More training courses

Forthcoming Events

    . . . . More Events is operated and owned by Adrio Communications Ltd and edited by Ian Poole. All information is © Adrio Communications Ltd and may not be copied except for individual personal use. This includes copying material in whatever form into website pages. While every effort is made to ensure the accuracy of the information on, no liability is accepted for any consequences of using it. This site uses cookies. By using this site, these terms including the use of cookies are accepted. More explanation can be found in our Privacy Policy