Weighing scales play an important part in many different industrial processes, but over time these precision instruments can become less accurate and less reliable.

A number of factors can negatively affect the performance of weighing scales over time such as their workload, age, method in which they are used, whether they’re moved from place to place frequently, temperature variations, power surges, dust, humidity and other confounding environmental factors.

Measurement is useless without correctly calibrated weighing instruments and so re-calibration is necessary to receive consistently accurate readings.

Weighing inaccuracies can be costly too.  Customers can be over or undercharged, production line re-runs may be required to correct mistakes, stock losses may be incurred, productivity will take be affected and there could be expensive unplanned downtime.

So, how often should scales be calibrated?

It’s an important question but given that there are so many variables involved and so many different types of scales, each of which has its own manufacturer’s recommendations, there actually isn’t a definitive answer. The point is that in order to deliver consistent, reliable and accurate measurements, any weighing equipment has to be kept in proper working order so the best policy is to ensure that your weighing equipment is inspected and maintained on a regular basis.

Regular calibration may also be required in order to comply with ISO or other quality assurance procedures, so the frequency of calibration will be determined by the contractual requirements.

Calibration intervals may also be determined by the contracts you have with customers – and in some instances, your weighing scales may have to be inspected by government agencies to ensure that they are legal for trade.  Additionally, being able to guarantee that you are providing your customers with 100% accurate product weights is hugely important and will strengthen relationships and build trust and confidence in your service delivery, which makes regular assessment of your weighing equipment all the more vital.

The company doing the calibration should issue an inspection and test report and if the weighing equipment is trade-approved, they should issue a Certification Form for the Trade Measurement Authority.

So, when it comes to the question of how often you should calibrate your scales, here are some factors to consider:

  • How often is the weighing scale used?
  • What is the scale used for? (Some applications may put the scale at risk of corrosion or rust and it will need to be cleaned properly and assessed more regularly)
  • How demanding are the operating conditions?
  • Is the scale subjected to extreme environmental factors such as heat, cold, frequent temperature variations, snow, lightning, humidity, dust or water?
  • Are the scales washed down repeatedly?
  • Where is the scale being stored and is it moved around frequently?
  • How old is the scale?
  • What are the manufacturer’s recommendations?

Ideally, the company doing the calibration testing should be a reputable service provider who can guarantee that their staff are fully trained, experienced and independently assessed as highly competent through accreditation by the Trade Measurement Authorities. If your weighing instruments (such as laboratory balances and precision platform scales) require NATA calibration reports and performance certificates, you need to ensure that you use a NATA-accredited metrology laboratory.