Instrument Calibration Services

UK based, we are an independent calibration laboratory providing UKAS accredited gauge, meter and instrument calibration services throughout the whole of the UK and Ireland.
With years of experience spanning all sectors and UKAS accreditations across multiple disciplines, we're a genuine "one stop shop" for all your measuring instrument services.

Calibration is the process of comparing a measuring instrument (the Unit Under Test or UUT) to a standard of known accuracy. The purpose is to determine the relationship between the readings indicated by the UUT and those indicated by the standard.

A calibration certificate would therefore ideally show the measured results for the UUT versus the measured results from the standard.

To provide confidence in the validity of the calibration results they must be traceable. This means that the results on the calibration certificate for the UUT are traceable to the standard used, and the results on the certificate for the standard are in turn traceable to the standard used for its calibration. And so on back to standards held by a national laboratory (Eg the National Physical Laboratory - NPL in the UK). Furthermore, each set of results in this unbroken chain should be accompanied by a quantified statement of the uncertainty of measurement.

The easiest way to demonstrate formal traceability is to use the services of a UKAS accredited calibration laboratory. A laboratory whose procedures, equipment and personnel have been independently audited to the international standard for the competence of testing and calibration laboratories ISO/IEC17025.

This is the uncertainty or doubt that exists about any measurement that is made. There will always be an element of uncertainty about any measurement no matter how carefully the measurement is made. If the measurements are carried out as part of a calibration, then the uncertainty should be reported on the resulting certificate. You can think of the uncertainty as the accuracy with which a measurement has been made.

Acceptance criteria is the criteria against which an instrument, gauge or meter is judged when it is calibrated. The Pass or Fail criteria. It is quite important that this is properly considered.

One might make the simple assumption that if a meter performs within the manufacturers spec then it is acceptable. But have you fully considered how the meter is going to be used, and what accuracy you require of the measurements you are going to make with it?

An acceptable level of accuracy might for instance be 25% of the tolerance applicable to the feature being measured or tested.

There are possibly many things that can influence the accuracy of a measurement, but perhaps the most fundamental are... uncorrected errors in the instrument used to make the measurement, "in service" drift or the ability of the instrument to reproduce its readings between calibrations, and of course the uncertainty attaching to the instrument calibration.

When all of these contributions have been combined they should be within the previously determined acceptable level of accuracy for the measurements to be made.

Basically, if an acceptable level of accuracy for the measurements to be made is first established, this will allow for the establishment of acceptance criteria for the measuring instrument when it is calibrated.

Simple reliance on whether or not an instrument conforms with the manufacturer's published accuracy specification, without consideration of any of the above, is not usually enough. In any case, manufacturer's specifications are notoriously unreliable as they are usually driven by the marketing department. We see many instances of brand new instruments failing to meet their published specifications.

It is probably fair to say that the vast majority of measuring instruments that are calibrated, are calibrated annually, then put back into service. It happens this way because it is an easy system to administer.

This is not really the best approach to take however. Most if not all measuring instruments will drift with time. An instrument's performance was known the last time it was calibrated, but how has it changed since that time. The newer the instrument, the more frequently it needs to be calibrated, until its ability to reproduce measurements over a period of time has been established and is well understood. A user might estimate a suitable recalibration frequency, based on previous experience of similar instruments used in similar environments, but it is only when the actual data from a series of successive calibrations of a particular instrument has been properly analysed that a meaningful recalibration frequency can be determined for that particular instrument.

There is no doubt that a properly organised calibration program can appear to be costly. And that cost is often the main consideration when the decision is made not to calibrate measuring equipment.

There can however be huge hidden costs and risks associated with using un-calibrated instruments. How does the cost of a product recall stack up against the cost of calibrating a couple of instruments? The truth is, properly calibrated measuring instruments, and proper understanding of the quality control of processes can bring huge benefits in terms of product quality and customer satisfaction.

Of course there will be situations where an instrument does not need to be calibrated. An example might be an electrical power supply whose output is normally monitored by a calibrated meter. Suitable controls should be in place however to ensure the power supply is not used "stand alone" with reliance on its own output meter which could be in error by a significant margin, yet give the impression that all is well.

Another example is the dilemma facing electricians...
UKAS Meter Calibration v Check Box. Read more about why Electrical Tester or Meter Calibration is important, and why it cannot be replaced by in service checks using a "Check Box".

The safest way forward is use the services of a UKAS accredited laboratory.

A laboratory whose staff, technical capabilities and management systems have been independantly audited and accredited to ISO/IEC17025.

By so doing you will have confidence that the laboratory has the competence and impartiality to consistently deliver the level of service you need, that is traceable and valid calibration results time after time.

Accreditation to ISO/IEC17025 goes way beyond the requirements of standards such as ISO9001.

A laboratory that is certified to ISO9001 alone has only had its quality management system certified, not its technical competence, and should not be considered a suitable alternative to a UKAS accredited laboratory.