What is calibration?

Your tool seems to be working fine, but how do you know it's measuring correctly? This is where calibration comes into play.

Calibration determines and documents reading differences by comparing an tool's measurement to a measurement standard (fixed equipment known to measure accurately). This is usually followed by adjustment of the tool.

This process checks whether the values ​​are within the acceptable range (tolerance level) for a particular application. If not, the equipment needs to be adjusted to ensure that the deviation between the current and required value is minimal and to restore the initial performance accuracy of the tool to provide higher precision. A calibration check can be performed after the tool has been adjusted.

Why is calibration done?

Tool and device performances decrease over time and every tool loses its accuracy to a certain extent. The example below shows how the torque of a BlueTork nutrunner used to tighten truck wheel lug nuts can change over a few years under normal operating conditions.

Although the torque value is the same, the actually measured value is different. For the first few years the value still remained within the tolerance range, but by the third year it had moved out of the tolerance range and the nutrunner needed to be adjusted to ensure it continued to produce accurate results.

Calibrating and adjusting tools ensures that their accuracy remains at the required level. This is important for 3 reasons:

• The tool operates correctly, maintaining the correct tightening torque over time 
• The company complies with standards and quality system legal requirements and therefore avoids possible legal consequences regarding product liability. If a company is ISO 9001 certified, it must calibrate its tools to ensure the quality of its final product and service 
• This process guarantees safety for both employees and customers.

A calibration certificate must be issued by a laboratory at the end of the calibration process.

Note: the test certificate is different from the calibration certificate. Test certificates only show the performance of the tools at a certain point in time.

How are tools calibrated?

Only laboratories compliant with the ISO/IEC 17025 standard can issue a valid calibration certificate. You can contact your local accrediting body to obtain a list of all accredited laboratories.