Top tips for choosing a calibration supplier

Paul Boughton

Industrial calibration services are widely available, from suppliers both big and small, but what should buyers look for when choosing a calibration partner? Matt Gypps offers 10 tips

1. Do your own research

Calibration services can be sourced in many ways, from word of mouth through to the internet, but the common denominator in determining the choice of a calibration supplier should always be your own research. Don’t take at face value what you see on a website, get out from behind your desk and go to visit your potential supplier’s laboratory. A professional website is no guarantee of competence, because it could contain stock images and in reality be a single engineer operating out of a garage. Calibration buyers need to see the evidence with their own eyes.

2. Ask for example certificates

A large percentage of purchasers who source calibration services are non-technical, which means it is easy for them to be misled about the robustness of the certification being offered. When calibrating a thermometer, for example, it is not acceptable to measure only one or two points – multiple points need to be measured along the scale. Good laboratories will offer multiple points as standard but will also work with the customer to help them determine if additional points are needed for their particular application.

3. Take a closer look at the uncertainty of measurement

In order to prove the compliance of a customer’s equipment, the measurement needs to be more accurate that the equipment under test. This is known as the test uncertainty ratio (TUR). As the accuracy of test equipment improves with advances in technology, the accuracy of calibration equipment required has to improve to maintain the required ratio. This equipment can be very expensive and may not be cost effective for some calibration companies to purchase. Using older, less accurate equipment may result in a poor TUR at which point the calibration company should discuss this matter with the customer. Ensure that uncertainties are included on the certificate and they are appropriate for the item that has been calibrated.

4. Watch out for hidden costs

If your calibration supplier has limited capability it could be generating hidden costs which are difficult to track and contain. For example if you are being forced to use five different suppliers to calibrate your full range of equipment, that equates to five different purchase orders and five different invoices that need to be processed – all of which can add to your cost base.

5. Don’t settle for speed over accuracy

Fast turnarounds are not everything. Quality of measurement is more important and should never be compromised for speed. The fact of the matter is, high level measurement takes time and certain equipment, such as dimensional test equipment needs time to stabilise to the right temperature, sometimes several hours. This is especially important for on-site calibration where mobile laboratories may not have the same level of environmental control as a permanent facility. A calibration laboratory that sells its services purely on the basis of speed could be cutting corners.

6. Review your supplier’s accreditations

Accreditations are important and customers should ask to see them. From a technical point of view ISO9000 certification is not enough. It does prove that the company has a Quality management system in place, but the audits do not go into the technical competence of the laboratory.  An ISO 17025:2005 accreditation proves that an independent body, such as UKAS has inspected the laboratory and assessed its calibration techniques, procedures and engineer competence for a specific capability. All UKAS Schedules are available to view online.

7. Ask about the full range of capability

It is not always cost effective for a calibration laboratory to invest in the equipment or expertise for a full capability in all types of instrument calibration and some quite rightly focus on a particular area of expertise. However some companies may offer an extensive range of calibration services, but when you examine the range of a particular parameter you could find that their capability in this field, and therefore the calibration service that they can provide, is very limited. Ask what your supplier does when a piece of equipment comes in for calibration outside their normal area of expertise.

8. Ensure your equipment is calibrated against its full specification

Sometimes equipment can be calibrated and customers told that it is “compliant” with the original OEM’s specifications, but the calibration has not tested the limits of the specification only the mid-range where it often has a better chance of passing. In the past, at Trescal, we have failed equipment because it does not reach its full published specification which has resulted in changes to a manufacturer’s data sheets. The bottom line is that for end user confidence, equipment needs to be compliant across its full specification unless otherwise agreed and stated on the certificate.

9. Ensure that any measurements are ‘traceable to national standards’

In order to ensure that measurements are equal worldwide, a system of international and national standards exist. Calibration companies must be able to prove that their own standards are traceable to national standards through a series of comparisons. Check the certificate and ensure that it contains information about the traceability of measurement so that you can prove your own traceability.

10. Look out for the added-value services

Low prices will usually mean a streamlined service, but this will mean that you miss out on the added-value services which could ultimately save you money. Free collection and delivery and free asset management are just two of the services which often get bundled into the calibration price and offer customers the opportunity to take cost out of their business. For a customer with a large pool of equipment there is huge potential to save time and money internally by using an external asset management service, particularly if it comes as part of a calibration package.

Above all, don’t be afraid to ask difficult questions. Defensive or muddled answers should set alarm bells ringing.

Matt Gypps is Deputy UK Technical Manager at Trescal.