Thermocouple Calibration: 3 Tips to Save your Business Money

Thermocouple thermometers are an amazing tool for many applications. With the ability to change probes for measuring various substances they are highly versatile. However, that versatility comes with a price. Every thermocouple thermometer and every probe have their own accuracy and level of uncertainty. Within a quality system, these levels of accuracy are accounted for by getting the unit and probe calibrated as a system to provide a recorded and traceable level of accuracy. If you use a single probe and unit combination this isn’t a problem, but as the need for different probes and multiple inputs increases, so does the cost of calibration. So here are 3 tips that could save you money off your next calibration.

1. Be aware of the different types of Thermocouple / Thermometer Calibration

There are three different levels of thermocouple calibration. Each has its own merits, and situations where it excels. Simply being aware and selecting the right calibration is the first step to saving you money.

1) UKAS Calibration (Full System)

UKAS calibration is the tip of the top and is our highest level of calibration. This calibration takes 1 probe and 1 unit of your choosing and measures them against the very best standards.

Pros: Produce legal documents that will stand up in court

Cons: Most expensive, only good for 1 probe and unit combination. Very expensive to get multiple probes or inputs calibrated as each probe / certificate combination must be calibrated separately. Instruments are rarely adjusted.

When should I use?
If your quality system states your equipment should be UKAS calibrated, then you have no choice. If your measurement application is critical and mis-measurement could cause harm, then we recommend always opting for UKAS.

2) Traceable Calibration (Full System)

A traceable full system calibration mimics the set-up of a UKAS calibration but is what is called a second-generation calibration where it is calibrated against UKAS calibrated instrumentation. This introduces a slightly greater level of uncertainty, which is documented on the certificate.

Pros: Cheaper than a UKAS calibration and slightly more flexible. Instruments may be adjusted to pull them back into specification.

Cons: Still only good for 1 probe and unit combination. Still very expensive to get multiple probes or inputs calibrated.

When should I use?
Traceable certificates are great for any quality system / auditable procedure than needs to prove the validity of its measurements. This is best used when the measurement is non-critical and poses no risk of injury or harm to people from the measurement

3) Traceable Calibration (Unit Only)

The unit receives a second-generation calibration. However only the unit is calibrated and any uncertainly introduced by the thermocouple probe is unaccounted for.

Pros: Cheapest option. Allows any probe the be inserted without nullifying the calibration

Cons: The least accurate calibration as the uncertainty of the probe is not calculated within the calibration.

When should I use?
If you have a thermocouple thermometer that requires regular switching of probes, then a unit calibration could be ideal for you. However, as the probe accuracy is not accounted for this must be considered and as such not used when measurements are critical.

2. Buy a dual/quad input unit

A common use of thermocouples is to simultaneously measure multiple samples. Unaware of their options, some customers purchase multiple units, and multiple probes, getting both calibrated. Thermocouple thermometers often come equipped with more than a single probe input. We sell both dual and quad input thermocouple thermometers. This allows you to purchase a single unit and multiple probes.

If opting for a simple unit calibration (without the probes), it is much cheaper to get multiple inputs on the same unit calibrated. For example.

Single Input Thermometer
Item Quantity Individual Price Total
TK-610B Thermometer 2 £60.00 £120.00
CAL-TK Unit Calibration 2 £50.00 £100.00
£220.00
Dual Input Thermometer
Item Quantity Individual Price Total
TK-612 Thermometer 1 £65.00 £65.00
CAL-TK2 Dual Unit Calibration 1 £65.00 65.00
£130.00

*Prices as of ATP website 2019.

Single Input Thermometer
Item Quantity Individual Price Total
TK-610B Thermometer 2 £60.00 £120.00
CAL-TKSYS System Calibration 2 £65.00 £130.00
£250.00
Dual Input Thermometer
Item Quantity Individual Price Total
TK-612 Thermocouple 1 £65.00 £65.00
CAL-TKSYS System Calibration 2 £65.00 £130.00
£195.00

*Prices as of ATP Website 2019

3. Self-reference additional probes and inputs

If you have an application which requires the use of multiple inputs and types of probes, typically you would get a traceable system calibration on each probe / unit combination. Instead, you can opt for a UKAS calibration on one input/probe calibration and use this as a reference for your other inputs with a similar setup. However, you must be aware that this is not a certified calibration.

Let’s take a look at this example. You have a TK-612 thermometer. You need to measure 2 air/liquid samples simultaneously using the probes that come supplied with the unit.

Option 1: Calibrate Everything with a Taceable Calibration
Item Quantity Individual Price Total
TK-612 Thermometer 1 £65.00 £65.00
CAL-TKSYS Unit Calibration 2 £65.00 £130.00
£195.00
Option 2: UKAS Calibrate 1 Probe / Unit Combination
Item Quantity Individual Price Total
TK-612 Thermometer 1 £65.00 £65.00
UKAS-TK UKAS Calibration 1 £75.00 £75.00
£140.00

*Prices as of ATP website 2019.

In the second option, we requested input 1 to be UKAS calibrated with a supplied air probe. Now you have verified records, you can use the 2nd probe in the alternative input and use the UKAS calibrated input/probe as a reference to the current accuracy of the second input. You can expand this principle to other types of probe. Purchasing only 1 UKAS certificate per probe type.

Summary

So there we have it, 3 simple ways to cut costs when calibrating your thermocouple.

  1. Pick the right type of calibration for your application
  2. Use multiple input units where possible instead of multiple units
  3. Upgrade multiple input calibration to a UKAS and self-reference matching input / probe set-ups.

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