Looking after your load cells
Load cells are remarkably hard-working, robust and reliable technology, but over time their accuracy may start to diminish. Whether used regularly or continually for weighing, for example, you need to look out for the signs that your load cells need a little attention, and perhaps recalibrating or replacing.
Here are our top five potential issues to look out for. All the specifications quoted below are for our own brand 100 series low profile load cells, as an example. You can download the data sheet here:
1. Changes in temperature
Metal load cell and their strain gauges can be affected by major changes in temperature, which can affect their accuracy. Even the contrast between cold night and hot sunny days can cause errors. There’s no fix as such for this, except to try and position your load cells such that you maintain as consistent temperature as possible.
Our load cells have wide operating ranges, such as:
Storage Temp: -40 to +70 C
Operating Temp: -20 to +70 C
Compensated Temp: +20 to +70 C
2. Non-linearity and hysteresis
Every measuring devices will always be subject to some degree of error, even straight out of the box. For load cells, this manifests as non-linearity and hysteresis.
- Non-linearity is the weighing error over all your load cells. The bigger the change in load capacity, the greater the non-linearity.
- In weighing systems, hysteresis is “the difference in the results between increasing the load from zero and decreasing from maximum.” Again, the larger the load, the greater the potential error.
Our data sheets on our load cells shows the information for both non-linearity and hysteresis for the particular load cell type. For example:
- Non-Linearity: 0.05% of F.R.O or Better
- Hysteresis: 0.03% of F.R.O or Better
3. Creep
Hard-working load cells that are constant pressure, such a load cells under grain storage silos, will gradually become more inaccurate due to ‘creep’.
“Creep is the change in load cell output occurring with time while under constant load and with all environmental conditions and other variables also remaining constant.”
Once again, the higher the force applied, the more creep will happen. You can make creep adjustments to your data to account for this.
4. No Return to Zero
if you are measuring ever-changing loads using load cells, your load cells need a period of time to stabilise and return to zero when a vessel is emptied before the next load is added. If you refill before this has happened, the load cell measurement will not be accurate within the stated error tolerance range, for example:
Zero Balance: 0.5% of F.R.O or Better
Regular recalibration of your load cells will ‘reset’ the load cells and restore accuracy again. Contact us for details of our load cell recalibration services (https://www.loadcellshop.co.uk/calibration).
5. Check the cables!
Sometimes, it’s all too easy to overlook a simple issue when troubleshooting load cell errors – the cables and their connection. Depending on the load cells location, the cables could be affected by damp or water, causing cable connections to corrode and affect the load cell signal. Electromagnetic “noise” can disrupt signals too, from other equipment cables in the vicinity. Cables should also be insulated to resist current leakage, for example
Insulation Resistance: > 2000M Ohm
Recalibrate or replace?
All types of load cells need regular recalibration to ensure they are accurate and their data is reliable. However, there comes a time for even the most robust of load cells when their working life is over, and it’s time to replace it. Equally, your business may prefer to simply swap out old load cells for new rather than embark on the lengthier process of recalibration. Call us to discuss your options – we are more than happy to help.
Call us: tel:+441189310396
Email us: sales@loadcellshop.co.uk
Shop online: https://www.loadcellshop.co.uk/all-products
