Calibration, have you been wondering whether or not you and your company need it? What is Calibration anyway? Don't worry, you're not alone. This is without doubt the single most asked question by new customers here at ATP. So here is an explanation in lay terms to help you move forwards and make an informed decision. Calibration in its simplest terms, is a process in which an instrument or piece of equipment’s accuracy is compared with a known and proven standard. There are different types of calibration that conform to different standards. Some types of calibration will also include a service to bring instruments that fall outside of a standard back into alignment.
Do I need my instruments Calibrated?
In today’s industry, more instruments are being used without firstly being checked for traceable accuracy, yet the accuracy of the instrument could be the difference between wasting a whole measurement process, and being correct the first time. The question of if you need it or not is ultimately a decision you and your or your quality auditing team need to decide. There are no set rules in place that govern when an instrument should be calibrated and when it should not. That is of course other than those set by your own Quality Management Systems. If part of your company process involves measurement using any form of instrument then your standards may require that you can prove that the instrument provides accurate readings and can relied be upon to do what it says it does. If this is the case then yearly calibration is common practice and would most certainly be required.
The International Organisation for Standardisation (ISO)
Whilst no pre-determined standards are enforced. What do exist are a series of standards set forth by the International Organisation for Standardisation (ISO). One such standard is ISO 9001 which outlines principles a management system should follow to ensure customers get consistent, good quality products and services. Many companies choose to apply ISO standards to their own internal management systems and processes.
For example, a company may tailor its management system to follow ISO 9001 and then seek ISO 9001:2015 Certification from a certification body.
Note: The ISO do not provide certification themselves, this must be done through a 3rd party. A company will never be ISO certificated but will be certified to a set standard i.e ISO 9001:2015. The certification body would audit the processes undertaken with reference to ISO 9001:2015.
If adhering to ISO principles and standards, then it is highly likely your management system will state that your instruments must be calibrated to prove that parts of your process are performed within predefined parameters. Again annual calibration is the most common practice. If your company is certified to an ISO standard, then having all controlling instruments calibrated on a regular basis, and holding their calibration certificate on file is a mandatory part of the auditable procedure.
The Importance of Calibration
The importance of calibration is not just to check that the instrument’s displayed values are within specification, but also to help you understand the inaccuracy of the displayed values at specific points of measurement. When you’re calibrating an instrument, it is best practise to calibrate at points of measurement critical to the instrument’s application. For instance, it’s a legal requirement for food caterers and retailers to ensure hot-held food is kept at 63°C or above to avoid cultivating harmful bacteria, therefore it would be advisable to calibrate a thermometer at 63°C, or as close as possible. A calibration certificate proves that an instrument has been checked and verified against these critical points of measurement, and will list any errors the instrument has, giving you confidence to demonstrate to an auditor or customer that your instrument reading is within the specified accuracy, and is fit for your desired application. The certificate will be available for most instruments that are used in a professional environment where traceable accuracy is required. In a professional environment, it’s standard procedure to calibrate an instrument upon its purchase, and on an annual re-calibration basis, but if your instrument application demands a shorter period between calibrations, it’s often best practise to set-up an ‘automatic re-call’ procedure with a qualified laboratory technician. This way you’ll always be reminded when your instrument is due to be calibrated, and the instrument’s accuracy won’t be compromised without your prior knowledge. If you’re using an instrument that hasn’t been calibrated, it has to be considered that your measurement may be seen as unreliable and incompliant to national or international standards in a professional environment.
The Different Types of Calibration
Generally speaking there are two types of Calibration procedure. These are most commonly known as a ‘Traceable Calibration Certificate’ and a ‘UKAS Calibration certificate’. For the most part, the procedures are very similar but there are distinct differences you should be aware of before purchasing.
Traceable Calibration Certificate
Traceable calibration involves referencing your instruments against pre-calibrated devices so that a degree of error can be calculated. At ATP we reference your equipment against our own in-house instrumentation that has all been calibrated to UKAS standards. This is known as second generation calibration and ensures that your instruments are accurate to within the standards claimed +/- the possible deviation of our own instruments.
The main advantage of traceable calibration is that there is more flexibility in the testing and adjustment. This means that where possible, any instrument that produces readings that are outside of the claimed specification are adjusted back into alignment and re-tested. At least that's how we do it at ATP! This ensures that the instrument you send in is returned with guaranteed accuracy at the points indicated. This produces a certificate that meets national standards.
UKAS Calibration Certificate
A UKAS calibration is performed by a laboratory that has gained UKAS Accreditation. This means that the calibration laboratory has fulfilled the requirement of ISO/IEC 17025 and meets the technical competence requirements and management system requirements that are necessary to provide technically valid test results and calibrations. The management system requirements of ISO/IEC 17025 ensure that the laboratory meets the principles of ISO 9001:2015.
In short, a UKAS calibration certificate is an accredited certificate that is produced to international standards and is a legal document that can stand up in court. The downside to this level of calibration is that the instruments will not be adjusted if they fail to meet standards. Meaning they must be adjusted and re-sent for calibration. This can become a costly procedure if your instruments routinely fall out of specification.
What type of Calibration is right for me?
Once again, you tell us! The level of calibration should be outlined within your own quality management system. This is dictated by the precision required by the reading and the importance of its result. For example, a factory may require working conditions to between certain measurements. A daily reading is taken as a guideline to see if they are ever in danger of going outside of these conditions. As such a traceable calibration certificate would likely be adequate. Eventually however, the conditions in the factory change over time and become dangerously close to being unacceptable. They call in a specialist to measure the precise conditions and determine if they need cease production. His equipment is much more precise and would likely be UKAS calibrated due to the importance of precision required in his role. If in doubt, we advise your speak to your own quality assessor / auditor to check which you need.