A Complete Guide to Equipment Calibration

Drawing on his 15 years’ experience in the industry, Radek pointed out a key misconception surrounding calibration. “Calibration is often mistaken to mean adjustment. That’s not always the case. In many instances, calibration means verification of what the instrument reads at a very specific point.”

For example, a thermometer calibration involves a verified analysis of its temperature accuracies. Most laboratories verify the thermometer’s accuracy at three different temperature points, such as -18°C, 0°C, and 100°C.

If the instrument is adjustable, then the calibration process can involve modifications. If it is not adjustable, equipment is returned with a calibration certificate stating any divergence, such as -18.2°C, 0.3°C, and 100.5°C.

The importance of this cannot be overstated. Yes, certification proves that your instruments are traceable to a UKAS-accredited standard – in Klipspringer’s case, international standard ISO/IEC17025. Calibration certificates also enhance company adherence to food safety standards and are one of the most common requests made by assessors during audits.

But, most crucially, certificates also explicitly demonstrate the exact accuracy of an instrument. Neither subjectivity nor error are tolerable when it comes to food compliance. Customer safety is at risk – particularly with temperature, where the difference between safe and unsafe food could be as little as one degree.

In conversation with Radek, he outlined four specific factors that determine the necessary frequency of calibration. These are:

1) Equipment type

In general, most equipment requires consistent calibration, although, logically, certain types of instruments require recalibration on a more regular basis than others. Humidity meters, refractometers, and callipers are all examples of instruments that should be frequently recalibrated.

2) Usage

A general rule of thumb here: as a piece of equipment receives more use, the frequency of its calibrations must increase proportionately. For example, thermometers are usually expected to be calibrated at least once a year – but Radek says some food businesses send their units in for calibration every 4-6 months because their usage is so high.

3) Likelihood of readings changing without recalibration

For equipment which sees regular shifts in readings, more frequent calibration is required. These might include data or process loggers. Conversely, it is not as essential to repeatedly recalibrate instruments which maintain the accuracy of readings for longer.

4) Capacity to calibrate the equipment on-site

Some food businesses are able to calibrate their equipment on-site. For instruments like pH and conductivity meters – which are expected to be calibrated daily – it makes sense to keep the majority of these verifications in-house, with occasional external confirmations.

Radek underlined the importance of an external validation procedure to confirm that units are still working within their specification. Cross-checking confirms in-house calibrations and drives compliance.

The below outline is based on our internal calibration process at Klipspringer, overseen by Radek as Laboratory Manager.

Calibrations that fall within the UKAS-specified -30°C to 150°C range are always carried out internally, according to the following procedure:

1) The customer communicates with the lab team and raises a quotation

2) The customer sends their equipment to the laboratory

3) This equipment is booked in; the customer is sent an email confirmation, specifying exactly what the lab team is going to do with the equipment

4) If the equipment is booked in for UKAS calibration, the customer will receive an email with confirmation of temperature point the unit will be calibrated at

5) A lab technician is designated to the task – they either begin the calibration immediately, or carry out any necessary technical repair beforehand

6) Equipment sent in for UKAS calibration will need to be stabilised at an ambient temperature of 20°C ±4 for up to 24 hours before performing the calibration

7) Once repaired and/or calibrated, a certificate is issued to the customer and uploaded to the Audit Portal

8) The lab job is passed onto the Service Team, who send an email quotation to the customer to confirm any final details

9) Following customer approval, equipment is returned to the customer, usually on the same day, or at least within three working days

Defined as the time elapsed between the start and end of the calibration process, calibration lead time is a crucial metric in the food industry used to calculate how quickly and efficiently your equipment can be calibrated, returned, and operating once more.

By making enquiries among our customers, we ascertained that, on average, most companies in the industry operate with calibration lead times of 4-7 days. Sometimes these turnaround times are as lengthy as 2-3 weeks!

According to Radek, there is no hard-and-fast rule for lead times. But there are two factors that markedly influence lead times: the number of calibration orders at any one time, and the resources available to manage them.

It is also true that some companies simply prioritise calibrations more than others. When asked why Klipspringer are able to guarantee that all in-house calibrations are fully completed within three working days, Radek replied:

“We have several skilled lab workers constantly on the calibrations, completing each with meticulous attention. It comes down to efficiency and experience.”

Temperature

• Data Loggers
• Process Loggers
• Liquid ‘In-Glass’ Thermometers
• In-House Thermometer Verifiers (also known as Temperature Simulators)

Meters

• pH and Conductivity Meters
• Reflectometers (measure the reflectivity of objects)
• Anemometers (measure the speed of wind or gas currents)
• Refractometers (measure the index of refraction)

Humidity

• Handheld Units
• Loggers
• Dry-Block Calibrators

Other

• Callipers (measure the dimensions of an object)
• Scales and Weights
• Oil Quality Measurement
• Hygiene Monitors
• Light Meters
• Gas Analysers

Radek emphasised that, while this list encompasses most of the instrumentation most frequently calibrated at Klipspringer’s in-house lab, it is not exhaustive – other types of equipment will also need calibration.

If you’re unsure about anything calibration-related, please contact our customer service team at: 01473 461800. A member of our team will consult one of our Calibration Experts about your specific requirements, before giving you all the relevant information.

Alternatively, you can read another research-led article we wrote detailing how to understand your UKAS calibration certificate.