November 22, 2019

What is Calibration and Why Have It Done?

What is Calibration and why should I have it done?

Calibration is the process of checking measuring equipment or instruments by comparison with a standard (another instrument or artefact of known properties). The instrument or artefact used in the calibration process must in turn be calibrated with equipment that has an unbroken chain of calibrations back to international standards.

Historically, traceability was back to National Standards. The traceability to international standards uses the International System of Units (SI)

Often calibration includes the adjustment of the instrument to bring the measurement back into predetermined tolerances.

Why Calibrate?

Calibration is important to ensure the accuracy of the measurements you are taking.

In the simplest form, if you buy 1Kg of apples, how do you know you have 1 Kg and not 0.9 kg or 1.1 kg? Furthermore, if you buy 1kg of apples from another country you need to know it’s the same as buying 1 kg in the UK.

Is calibration a requirement of the ISO 9001 : 2008 quality management system?

Yes!! If you take any measurements in your manufacturing, service or testing processes then the equipment used must be calibrated on a regular basis and these calibrations must show traceability back to international standards.

Detailed records must be held recoding the performance of the equipment being calibrated. These records or calibration certificates must be reviewed and retained in accordance with the requirements of your quality manual / procedures.

How often do I need to calibrate my equipment or Instrument?

The main questions to ask how important are the measurements to my process or product and how likely is it my equipment will drift out of specification between calibrations ? For most equipment, a 12 month cycle is sufficient.

To determine the correct cycle for critical equipment, start with a 6 month cycle and then after two calibrations or so without adjustment, increase this to 12 months. Sometime it’s possible to increase this further to 18 or 24 months.

Stable standards like weights, might only require calibration every 3 to 5 years, depending on how they are used and how often. This includes what the environment they are used in weights that are only used in a clean laboratory will of course be less susceptible to dirt and therefore change.

Weighing scales and balances that are product or process critical especially ones with a higher resolution will require calibrating every 6 months.

It’s often quite easy to set up a simple user check, either before the equipment is used or once a week etc. For example, if you had a weighing scale that weighs up to 2 kg, you could purchase a 2 kg and 500 gram calibrated weight, to check the scale with.

This can be helpful to increase the calibration cycle intervals, while maintaining confidence in the measurements you are taking. Although this isn’t a replacement for a full and proper calibration across the full range of an instrument by an experienced engineer, but it will help to highlight when there is a potential problem lurking.

AML Instruments can calibrate in excess of 500 different instruments all to ISO 9001 approved procedures, please visit our services pages for more details.

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