Thermocouple Calibration and RTD (Pt100) Calibration - UKAS Accredited

Why do thermocouples need calibrating?

Whilst thermocouples are robust temperature sensors and cover a wide temperature range, the voltage they generate can be prone to drift over time and exposure to certain atmospheres. Because thermocouples and associated equipment are usually critical to the processes they monitor, annual calibration is recommended to monitor any potential drift and to ensure the continued efficacy of the sensor. For some applications, for example those that see a large cycling of temperatures, calibration should be performed more frequently.

What is Thermocouple Calibration

A thermocouple is a simple but reliable device widely used for temperature measurement in industrial applications. Thermocouples produce a voltage corresponding to a difference in temperature between a measuring junction and a reference junction. The process of calibrating a thermocouple involves comparing the thermocouple output measurement against a known reference standard at a known temperature.

How to calibrate a thermocouple

There are a few ways to calibrate a thermocouple. The most accurate way is by using a Fixed Point cell where the thermocouple's output is measured against a number of fixed points along the International Temperature Scale developed in 1990 ITS-90 at the fixed point transition of various metals along the scale. Whilst this is the most accurate method of calibration, the temperatures are not always convenient or useful in practical terms for the intended use of the thermocouple. For example the melting point of gallium is 29.7646 °C which is not a temperature most thermocouples will be used at. However, the triple point of water (0.01ºC) is used quite regularly in our laboratory.

By far the most popular type of calibration procedure our lab technicians perform is the comparison method where the test sensor is placed in a stirred liquid bath, furnace or dry block calibrators at a specified temperature and it's output is compared against a known reference thermocouple or RTD Pt100 thermometer placed alongside the test thermocouple in the furnace. The sensor can thus be calibrated at virtually any temperature required. Our laboratory can calibrate sensors from liquid nitrogen right up to 1590 degrees celsius as shown in the measurement uncertainty data below.

Specialists in Thermocouple Calibration and RTD (Pt100) Calibration

TC Ltd specialise in thermocouple calibration and RTD calibration and we are proud to offer a wide variety of industry sectors with accurate and traceable In-House or UKAS (United Kingdom Accreditation Service) accredited calibration. This service is applicable for thermocouples, RTD sensors, instrumentation and cables under the scope of ISO/IEC 17025 & ISO 9001, all within our fully UKAS accredited calibration laboratory.

With the drive towards higher product quality standards and energy efficiency, end users are demanding more certainty and traceability from the products they purchase. A speedy, economical and reliable calibration service is provided in all respects. Significant investment has resulted in our UKAS accredited laboratory offering a world class service in terms of both CMC (Calibration & Measurement Capability) and volume throughput.

UKAS or Traceable In-House Certification of Thermocouples and RTD Sensors

Traceable In-house or UKAS accredited calibration is available for Base and Noble metal thermocouples and RTD sensors (Pt100) performed within our fully accredited laboratory.

Calibration is usually by comparison, traceable to National Physical Laboratory primary standards, against SPRTs or Type R reference thermocouples from -100 to +1590ºC. Fixed point calibration also available at -196ºC.

Measurement Uncertainty for Thermocouple Calibration and RTD Calibration

Our uncertainty of measurement is listed below for various ranges for thermocouples and RTD sensors:

Type of Sensor Range Calibration and Measurement Capability (CMC) Expressed as an Expanded Uncertainty
Resistance Thermometers Liquid nitrogen (-196ºC)
Triple point of water (0.01ºC)
-100ºC to -30ºC
-30ºC to + 20ºC
20ºC to 90ºC
90ºC to 200ºC
200ºC to 400ºC
400ºC to 620ºC
Thermocouples -
Noble Metal
20ºC to 200ºC
200ºC to 400ºC
400ºC to 620ºC
620ºC to 1100ºC
1100ºC to 1200ºC
1200ºC to 1330C
1330ºC to 1590ºC
Thermocouples -
Base Metal
Liquid nitrogen (-196ºC)
-100ºC to -30ºC
-30ºC to + 200ºC
200ºC to 400ºC
400ºC to 620ºC
620ºC to 1100ºC
1100ºC to 1200ºC
1200ºC to 1330ºC



International and Industry Specific Standards

Calibration can be performed to meet the requirements of most international and industry specific standards including AMS2750F, IEC 60584-1, IEC 60571, ASTM E220, ANSI MC 96.1, ASTM E235, ASTM E608, ASTM E839, GDCD16 & BAC5621K. We can also perform batch and reel calibration on selected material to ensure the best results possible when adhering to these strict standards.

Other Calibration

Electrical simulation for instrumentation calibration and surface measurement is also available as well as calibration of sensors and instrumentation together as a system.

International Calibration Bodies

NPL is a signatory to the CIPM MRA (Mutual Recognition Agreement) and as such results shown on our certificates can be considered as being traceable to all other NMIs (National Measurement Institutes) who are signatories to the MRA including NIST.

Enquiry Form

1. Type of Calibration

2. Number of Sensors

3. Calibration Points Required

4. Type of Sensor

4a. Sensor diameter (optional)

4b. Sensor Length (optional)

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Your Name




Additional Information

If your enquiry is for more than one style of sensor, please email us with your requirements or use the box below

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Thermocouple Sensors
Mineral Insulated Thermocouples
Thermocouples with Mini Plug
Thermocouples with Terminal Head
Thermocouples with Cable
High Temperature Thermocouples
General Purpose Thermocouples
ATEX/IECex Thermocouple Sensors
Ceramic Thermocouple Sensors
Fast Response Thermocouple Sensors
Autoclave Thermocouple Sensors
Surface Measurement Thermocouple Sensors
FEP Insulated Thermocouple

Platinum Resistance Thermometers
Mineral Insulated RTD Pt100 Sensors
Rigid Stem RTD Pt100 Sensors
Hand Held RTD Pt100 Sensors
Surface Measurement RTD Pt100 Sensors
RTD Pt100 Sensors with Cable
RTD Pt100 Sensors with Mini Plug
Autoclave RTD Pt100 Sensors
RTD Pt100 with Terminal Head
ATEX/IECex Platinum Resistance Thermometers
Fast Response RTD Pt100 Sensors
Air Temperature RTD Pt100 Sensors
Magnetic RTD Pt100 Sensors
PVC Single Pair Thermocouple Cable
PFA Single Pair Thermocouple Cable
Fibreglass Single Pair Thermocouple Cable
PVC Multipair Thermocouple Cable
PFA Multipair Thermocouple Cable
Fibreglass Multipair Thermocouple Cable
PVC RTD Pt100 Cable
PFA RTD Pt100 Cable
Fibreglass RTD Pt100 Cable

Miniature Thermocouple Connectors
Mini Thermocouple Connectors – 220ºC Rated
Mini Thermocouple Connectors – 350ºC Rated
Mini Thermocouple Connectors – 650ºC Rated
Mini Thermocouple Connector Accessories
Mini Thermocouple Connector Panels
Mini Three Pin Connectors

Standard Thermocouple Connectors
Standard Thermocouple Connectors – 220ºC
Standard Thermocouple Connectors – 350ºC Rated
Standard Thermocouple Connectors – 650ºC Rated
Standard Thermocouple Connector Accessories
Standard Thermocouple Connector Panels
Standard Three Pin Connectors
Hand Held Indicators
Panel Indicators
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Temperature Controllers
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Temperature Calibrators
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Dry Block Calibrator
Temperature Dataloggers

Temperature Accessories
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ATEX/IECEx Compression Fittings

UKAS Calibration Services

Pressure Gauges
Pressure Transmitters

© 1998- TC Ltd., P.O. Box 130, UXBRIDGE, UB8 2YS, United Kingdom
Tel.: 01895 252222, Fax: 01895 273540, Email:
© 1998- TC Ltd., P.O. Box 130, UXBRIDGE, UB8 2YS, United Kingdom
Tel.: 01895252222, Fax: 01895 273540, Email: