CALIBRATION
THE IMPORTANCE OF ACCURACY
Martin Westover, from Signatrol, looks at some of the key
questions asked about calibration, and
outlines its importance as part of a robust quality control system
he calibration of equipment is an essential part of any quality control system, such as ISO 9001:2000. While your record keeping may be meticulous, if the equipment you use to record the information is not accurate, the records are meaningless. All quality systems require that the measurement equipment used to verify or control quality must be regularly calibrated. All calibrations must be traceable to national or international standards (ISO 9001: 2000 section 7.6). A record of calibrations must be kept and corrective action taken when measurement equipment is found to be out of specification. This equipment must be calibrated either at regular intervals or prior to use.
T
parameter drifts between calibrations. Using this method, a model can be created that defines the maximum period between calibrations.
Whenever calibration is carried out, it must also be traceable to an approved laboratory. Test equipment must be adjusted as necessary, identified as being in date and tamper protected.
How often do I need to calibrate my equipment? This depends on:
• the quality and stability of the measuring equipment
• the initial accuracy specification • the importance of the absolute measurement accuracy
• whether there is a secondary back-up device
• manufacturers’ recommendations Based on this information, a calibration schedule can be created to ensure that test and measuring equipment are functioning within expected tolerance limits. It’s important to understand that the calibration values may change over time and will require periodic recalibration to be maintained within acceptable limits.
A calibration manager will often rely on manufacturers’ recommendations based on the assumption that they know their product better than anyone else and have conducted tests at the design stage. Alternatively, a calibration manager may choose to check the calibrations at short intervals (i.e. every three months) and record the amount the
12 JUNE 2025 | PROCESS & CONTROL
By optimising the interval between calibrations, unnecessary calibrations can be minimised and unnecessary costs avoided. Furthermore, this will improve compliance with regulatory directives and ensure maximum compliance with reliability targets. Do I need a calibration certificate with a new product? A new product has almost certainly been calibrated by the manufacturer with certified calibration equipment. Therefore, it is fair to assume that the product meets the published calibration specifications. Many customers ask for a certificate of conformity to confirm the product’s compliance and they deem that satisfactory to establish the initial calibration schedule. However, regarding critical applications, some customers require a valid calibration certificate and ask for this as an additional safeguard. What is Validation? Validation is performed by a third-party company who then provides a calibration certificate that is UKAS traceable which is then retained by the customer as part of their records.
What does calibration management involve? Calibration managers must ensure that:
• each piece of equipment is calibrated according to the specified schedule • each piece of equipment is marked with an appropriate label which shows a unique reference number, the calibration date and the date the next calibration is required • calibrations are inviolate and cannot be altered by unauthorised personnel • record of the calibration is maintained and retained for historical purposes Signatrol’s Calibration Service
All Signatrol data loggers have a calibration date reminder function. This means that users do not need to operate a separate re- calibration reminder system. The interval between calibrations is set by default to 12 months but can be adjusted by an authorised person. A reminder is shown on the screen of the data logger when the calibration is due. This reminder is reset at the time of calibration. Signatrol offers a fast turn-around temperature and humidity calibration service for our own as well as other brand data loggers and handheld thermometers so helping to minimise disruption and cost. When we calibrate our own brand equipment, the calibration date is reset. This does not occur when we calibrate other brand equipment. At Signatrol, we offer a UKAS 17025 traceable temperature and relative humidity (RH) calibration service. It is cost effective and can be turned around within 5 working days, where the data loggers are then returned with a UKAS traceable calibration certificate. We use UKAS ISO 17025 accredited equipment to carry out temperature and humidity calibration, and National Physical Laboratory (NPL) accredited equipment to deliver our process signal calibration services. We can also supply full UKAS ISO 17025 accredited calibration certificates if required. Each piece of equipment that we calibrate is issued with an individual calibration certificate, which is retained for a minimum of ten years If you are supplying a data logger to the United States and need traceability to NIST, UKAS certified thermometers are recognised as an acceptable alternative. Through several international agreements, UKAS has been determined to calibrate to the same international standards as NIST.
Signatrol
www.signatrol.com
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