A load off your mind: how to choose the right load cell for your materials testing
The mantra ‘test, test, test’ isn’t just for viruses. Testing of materials and products to ensure their safety and quality is happening every day across the world. One of the key methods is force testing, measuring how a given material or product responds to the application of force. And load cells are crucial to the accurate and consistent measurement of force.
Force exerted on an object can either be:
- a push, resulting in compression
- a pull, resulting in tension
Force can be measured in Newtons (N) or pounds-force (lbF). At The Load Cell Shop, we show the working range of our load cells in Newtons (N).
Most materials testing is done using a universal testing machine, or UTM, which exerts force on an object that is both constant and repeatable. These versatile machines can perform mechanical tests on materials including tension, compression, bend, peel, shear, and tear tests. Whatever the test required, in a UTM, load cells will be used to measure the the test object’s response to the force applied.
Sharing UTMs
UTMs are often hard-working machines, required to test a variety of materials to (literally) breaking point. They might need to test something delicate one day, an a robust material the next. In this case, there is no “one load cell fits all’’ solution. So, many UTMs allow users to swap out load cells, so they can use one that has the right operating range for the job.
Keep a stock of ‘ready to use’ load cells will ensure your testing facility is making the most of your UTMs. When choosing your range of load cells, you should consider:
- maximum capacity
- overload capacity
- mechanical failure limit
- accuracy
Maximum capacity and overload capacity
If you’re consistently testing materials that break within 10% of the load cell’s maximum capacity, you’re probably pushing it too far. Swapping to a higher capacity load cell will ensure you’re not in danger of overloading the load cell, and also allowing extra capacity for testing other materials. So, for example, if you’re pushing your 10kN load cell too hard, swap up to a 20kN and give yourself the option to now test materials up to 18kN with confidence.
Having said that, the overload capacity of a load cell will allow for the odd transgression when you test higher than its capacity. This is because the capacity level is set for regular use, whilst the overload capacity is to protect against inadvertent overload. The overload percentage do vary between the types of load cells. For example:
- Our 900 series feature Over Load Characteristics of 500% with no loss in Calibration (300% > 250N), and 500% with no Structural failure (300% > 250N).
- For our 100 series of low profile load cells, the Over Load Characteristics are 150% Safe Overload and 200% Ultimate Overload.
Using more than one load cell
If you are testing materials with very different breaking forces, you might be tempted to use a single load cell which is capable of testing the stronger material and use it for both. However, this will affect the accuracy, as the percentage range will be greater overall. So, instead, consider swapping out the load cells between tests using a quick-change adaptor, or use a ‘piggy back’ adaptor that allows the lower capacity load cell to be attached to the larger.
Help with designing your testing set-up
At the Load Cell Shop, we’re always more than happy to discuss your requirements, and help you work out the best solution to your materials testing load cell challenges. We design and manufacture our own brand of own load cells here in the UK, which are used in UTMs here and abroad. We’ve also helped design bespoke solutions for unusual testing requirements, from motor racing to trampolines!
Call us to discuss your load cell requirements, or if you know what you want, buy them online right now at our online load cell shop.
