Quick Tips for Balancing Load Cells

Whether you use bathroom scales, digital kitchen scales, spring scales – or any other measuring instrument, for that matter – you know the importance of zeroing it before it’s used. Failure to do so results in a shift in weight and thus, an incorrect reading on the scale. Now let’s think about the load cell in your testing system, which is just like a scale …

Prior to testing a batch of specimens, you should ensure that your load cell is properly calibrated and balanced – both actions are done right in the software. In Bluehill^® 3, this can be done from the console at the top of the screen. Simply click on the load cell icon, and then click "Calibrate". We refer to this as a software calibration (or “soft-cal”), which also balances the load cell.

Here are some soft-cal quick tips:

1. We recommend that the machine and load cell be switched on for about 15 minutes prior to performing a soft calibration. This allows the device to warm up, reducing the chances of drift.
2. Make sure you are not gripping a specimen when you perform a soft-calibration. It is okay to leave the upper grip or fixture attached to the load cell during the calibration – but it is also okay to leave it off. Just remember to perform an additional balance once the grip or fixture is added to the load cell.
3. Again, do not balance the load cell once the specimen is loaded into a grip or fixture. The force you see is real mass of the specimen, or force on the load cell. Balancing out this load would be like balancing a scale after you have put one foot on it (Note: this means the load cell should not be auto-balanced after preload). 
4. Though many systems will automatically recognize a load cell and restore its previous calibration every time it is plugged into the system, it is good practice to perform this soft-cal regularly, especially if swapping load cells. What does regularly mean for your system? Contact us, and we’ll help you figure it out.

Remember that a soft-calibration is not a replacement for on-site verifications by Instron Professional Services on a regular basis. For most laboratories, this means at least once a year, but your industry standards or internal protocols may differ.