Temperature calibration document library

This document outlines the design and calibration of high-accuracy, fully waterproof platinum resistance thermometers (PRTs) developed for continuous submersion in temperature-controlled water jackets. It describes custom-engineered probes featuring Inconel sheaths, sealed cable glands, and long low-loss cables, delivering performance beyond IEC 60751 tolerances. The whitepaper highlights complete system calibration with ISO 17025 traceability and measurement uncertainty better than 15 mK for demanding industrial metrology applications.

This whitepaper explains how Isotech delivers high-accuracy, traceable on-site calibration for embedded glass and metal temperature sensors used in analytical and distillation systems. It details a custom-engineered solution involving bespoke thermal blocks and angled reference probes, enabling reliable calibration of short, irregularly shaped, non-removable sensors. The document demonstrates how lab-grade accuracy and ISO 17025 traceability can be maintained even in complex, real-world process environments

An NPL study of the performance of 14 resistance bridges which were available for testing at NPL, consisting of a range of manufacturers and types, has been evaluated and expressed in terms of the standard deviation of the bridge errors over a given range of ratios, namely s.

Published in Cal Lab Magazine and reproduced with permission; this article looks at the calibration of thermometry bridges. Thermometry bridges play a crucial role in temperature measurement, particularly when it comes to the interpolation of the Standard Platinum Resistance Thermometer (SPRT) specified by the ITS-90. However, to achieve precise and reliable results, it is essential to calibrate these bridges accurately.

The accuracy of the Cold Junction Compensation (CJC) sensor in a temperature indicator is critical in order to make accurate measurements with thermocouples. Read our white paper exploring cold junction compensation, how to improve accuracy and calibrate using double junction thermocouples, and using a double junction to calibrate thermocouple indicators with electrical stimulation.

The automation of temperature calibrations has become more widespread in recent years as the demand from industry has grown and workloads have increased. Significant time savings and the ability to produce tailored calibration certificates has enabled the metrology community to actively service this need. Here, we show the equipment required and the configuration to automate the calibration-by-comparison of thermocouples and platinum resistance thermometers in the temperature range -20°C to +140°C.

Highest accuracy temperature measurements rely on the best SPRTs, Thermometry Bridges and Standard Resistors. For the standard resistors, it is vital that they have a low calibration uncertainty. Isotech are able to calibrate your primary standards to the lowest of uncertainties. With our priority booking-in service, turnaround times can be as low as one week!

With resistance thermometers careful consideration should be given to the measuring current in order to minimise the "self-heating effect". A look at the construction of platinum resistance thermometers and how to determine and correct for this effect.

When an SPRT is strained, the platinum is being stretched and thinned (like a strain gauge) and the resistance increases. By heating the thermometer (annealing) and then cooling it in a controlled way, the crystal lattice of the platinum returns to its original condition and the resistance of the thermometer reduces. Annealing should be seen as part of the maintenance of a thermometer.

How to Electrically Calibrate a Temperature Indicator that has Cold Junction Compensation? When calibrating a thermocouple indicator that has cold junction compensation, a standard voltage generator cannot be directly connected to the thermocouple input. One method is to connect the voltage generator to a “double junction” of thermocouple to copper wires and to place this junction in an ice flask or 0 °C reference unit.