No matter what application you are using your scales for, you always want to know that they are accurate, right?  In this article we try to explain the general idea of how to calibrate a weighing scale.

Scales come in all shapes and sizes, for all manner of applications.  Some are for weighing jewellery, others for weighing people, and yet more for weighing machinery.

Testing the Scale

Scales will often arrive with you calibrated and ready to use.  However, there are sometimes reasons why scales can go out of calibration.  External forces or poor environments are the top reasons that this might happen.

It's always good to check your scales regularly, so if you have test weights available (or a known weight) then set this aside and periodically use the weight to test the accuracy.

It's important to use the right reference weight for the right scale.  No good in using a 1 gram weight to test a bathroom scale, it won't even register on the indicator.  Rather, aim to use a weight around 50% of the capacity of the scale, if not higher.

My Scales are Inaccurate

If you find that the weight on the scale is no longer accurate, or the scale won't return to zero, the first thing to check is if anything is obstructing the scale from working correctly.  Scales often require a downward force to register the weight, is anything stopping the weighing platform from moving down?  It doesn't have to be much to have a big effect.  If so remove the obstruction and test again.

If the scales calibration has genuinely changed, then proceed with the calibration process.

Calibration WeightsCalibrating the Scale

It is important at this stage to mention that you should not change any operating parameters whilst in the calibration menu.  Doing so could stop your scale from working all together, so you should always be careful when attempting to do this, or seek the help of a professional.

This process will vary widely depending on the scale or manufacturer, however the principle is usually the same.

Calibration modes are usually entered into with a combination of button pushes.  Some will be with the press of a button whilst you are turning the machine on, others will be by pressing a dedicated calibration button on the front panel, others still will have a hidden button inside the indicator that needs to be accessed by opening the machine.  In all cases, reading the instruction booklet that came with your scale should help you achieve this.

The first step is to calibrate the zero point of the scale.  This is the point at which you want zero to be displayed when there is nothing on the platform.  Make sure the platform is empty, the scale is stable and proceed to the zero calibration step.

Once that has been completed, the scale should confirm to you that it took its measurement correctly, and then ask you for a span calibration.

Again, some scales will have a fixed span calibration amount that you are forced to use, others will allow you to use your own calibration weight.  Whatever the method, you need to ensure that what you tell the scale is exactly what you are putting on the platform.

Try to use as heavy a weight as possible.  The closer the weight you are using is to the scales capacity, the better the scales accuracy will be.

The next step is to add on your chosen span calibration weight, tell the scale what the weight is you are putting on if it allows you to, and then hit the submit/enter button.  You will hopefully be greeted with a calibration successful message if all has gone well.  Take the weight off the platform, turn the scale off and then back on again and test again to make sure everything has been saved.

When not to Calibrate

Don't be tempted to calibrate a scale that is used for retail purposes, medical purposes or is in any way sealed to stop the recalibration process.  Generally speaking, these scales would be Trading Standards Stamped and would need to be re-verified if the calibration was altered in any way.  Seek professional help for this purpose or speak to your local trading standards office for advice.

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