The Ultimate Guide to Calibration

All electronic measuring equipment, including electronic scales, thermometers, noise and vibration meters, can “drift” with time, but the reason you should calibrate your meter varies based on the type of equipment and the application it’s used in.

Why Should I Calibrate my Meter?

You may be confident that your measurements are correct if your metres are validated against a known source and have suitable certification. This is especially important if you’re taking measurements to follow a set of standards or laws, because non-calibrated equipment may give you substantially inaccurate results and may mean you are not compliant with the rules.

How often should a meter be calibrated?

Although it’s common knowledge that meters must be calibrated at some point in order to remain accurate, we’re frequently asked, “How often does my Meter need to be calibrated by a calibration lab?” Answering this question is both simple and difficult, depending on several aspects.

Here’s the simple answer:

The maximum interval between calibrations as advised in the UKAS document LAB 23 ‘Traceability for Equipment Used in Acoustical Testing’, which looks at different types of measurement equipment and considers the calibration period based on the nature and typical use:

• Dose meters – 1 year, although there should be an extended level of testing every other year
• Sound Level Meters to IEC61672 – 2 years
• Other Sound Meters (built to older or different standards) – 1 year
• Calibrators – 1 year
• Vibration Meters – depending on what type of vibration meter you are wanting to calibrate, we recommend yearly calibrations, but at the end user’s own risk they may choose to have it calibrated to a maximum 2 years
• Barometers (as supplied with Castle Class 1some older calibrators) – 1 year

All of the figures stated above are guidelines of for the maximum interval, and they assume that equipment is in regular use and are supported by good working practice. It may be appropriate to calibrate your equipment more frequently if it is in In non-typical use, such as:

• in areas with high or low moisture,
• in extreme temperatures, or
• where equipment is used irregularly.

As you can see, the general statement that equipment is okay to be calibrated every 2 years largely isn’t true, so you should be aware that this should at very least be reviewed regularly!

And please don’t forget that a proper calibration is not just a few points checked with an acoustic calibrator – we are talking about a full check of the electrical performance of the equipment at multiple points of frequency and level without the microphone fitted, followed by acoustical checks also at multiple frequency and level points, with the microphone included as part of the system – beware ‘cheap’ calibration houses as you will get what you pay for!

There are many other factors you should also consider:

Sticking with sound measuring equipment, there are further considerations to make, although many of these will equally apply to any measurement equipment.

• Instrument specifications and manufacturer’s instructions – What does the manufacturer recommend?
• Any requirements of the test specification – Does the application standard or law you are using specifically define a maximum calibration period?
• Expected use of the equipment – heavy use or regular exposure to harsh environments should shorten the calibration period.
• Review of calibration history – The calibration period should be reviewed and changed if necessary; a history of stable results may increase the period required.

There is one further point that you should consider and that is whether you are ever likely to have to rely on your measurements in court in defence of a noise induced hearing loss claim or as part of an environmental dispute or planning application. In this case, all equipment should be calibrated at least annually. You won’t find this point in any UKAS guidance but it is just something we have learned first-hand with our experience in these situations.

Thermometer Calibration

Temperature is a commonly monitored metric in industrial operations. To sense and control process temperatures, a wide range of mechanical and electrical thermometers are utilised. Regular calibration of these thermometers is crucial for guaranteeing consistent product quality and regulatory compliance in various businesses. An example of some of these applications are:

• in hygiene compliance of food temperature
• occupational exposure to heat and heat-stress
• quality control and manufacturing processes
• Industrial process control

Most websites and calibration houses recommend annual calibration as a general rule, although there is some specific guidance on the subject from UKAS, who’s document, LAB 11 ‘Traceability of Temperature Measurement’ covers the calibration requirements of certain sensor types, such as Platinum Resistance Thermometers, Thermocouples, Liquid-in-glass Thermometers and Radiation Thermometers.

The requirements for calibration vary widely and for all types, the heavier the use, the shorter the calibration interval should be. The absolute maximum intervals are shown below although care should be taken as there are caveats in most cases.

• Reference Platinum Resistance Thermometers – 5 years
• Working Platinum Resistance Thermometers – 6 months
• Reference Thermocouples – 4 years
• Working Thermocouples – 1 year although replacement is often a good option where they are used in harsh environments
• Reference Liquid-in-glass Thermometers – 5 years
• Working Liquid-in-glass Thermometers – Annual checks with 5 years of calibration, although every 6 months for the first year
• Reference Radiation Thermometers – 2 years
• Working Radiation Thermometers – 3 months

Gas Monitor Calibration

Gas Meters should be calibrated every 180 days.

They are designed to protect workers against the unseen hazards of gaseous substances within workplace environments, they’re commonly employed in mines, pits, and other enclosed locations where gases are present. These usually work at certain PPM levels.

The calibration of these devices is critical. When a device isn’t calibrated, it won’t provide correct data, putting the tester’s safety at risk. When it comes to gas equipment, erroneous readings might be the difference between life and death.

For the majority of gases, Gas Monitor calibration is a low-cost expense with Four-Gas Meters charged less than £100 for traceable calibration certification.

What kinds of instruments do we calibrate?

We calibrate many different kinds of equipment across many industries, if you can’t see your equipment in the list below, call us and we will be able to tell you if we can do it.

• Air Pressure Meters
• Anemometers
• Audiometers
• EMF Meters
• Gas Meters
• Inspection and Test Equipment
• Light Meters
• Multi-Function Meters
• Sampling Pumps
• Sound Meters
• Tachometers
• Temperature Meters
• Vibration Meters

We occasionally work with external partners for calibrating specific items. If you would like more information on this, then please contact us.

What is the price of calibrating my meter?

The cost of calibrating a meter will depend on exactly which model of meter you have, and to what standard you would like it calibrated. For example, a Class 1 sound meter UKAS calibration will typically cost more than a Class 2 sound meter traceable calibration, just because of the processes involved in completing both types of calibration.

What some people do not know is that we offer different types of calibration level.

Check / Performance Verification – We will make sure that your kit is working as it should be, checking for any minor faults.

Castle Traceable Calibration – As our standard service, all of our traceable calibrations are carried out to national standards, ensuring that your kit is working how it should be.

UKAS – ‘United Kingdom Accreditation Service’ is an acronym for ‘United Kingdom Accreditation Service.’ It is the United Kingdom’s sole national organisation with legal jurisdiction to certify calibration laboratories. A UKAS-accredited company may legally guarantee that their calibration service meets the requirements of the BS EN ISO/IEC 17025:2017 standard. BS EN ISO/IEC 17025:2017 is the internationally recognised standard for laboratory proficiency in “testing and calibration.”

The highest possible calibration standard available in the UK.