World’s first practical Johnson Noise Thermometer

TRM are delighted to be working with METROSOL Limited, on the development of the World’s first practical Johnson Noise Thermometer.

Johnson noise thermometry (JNT) is a primary temperature measurement method, based on the fundamental properties of thermal variations in conductors.

Currently, all thermometers in use (thermocouples, platinum resistance thermometers) are secondary thermometers and are therefore prone to drift. This is because the temperature is not measured directly, instead a property of the sensor, such as resistance or EMF, is measured. The property is related to temperature by a calibration process.

This relationship is used to convert the measured property back to temperature while assuming the relationship has not changed. In practice, this relationship between the property and temperature can, and does, change with time leading to “drift” in the reported temperature.

This tends to be more common in harsh environments, where factors such as contamination of the sensor, changes in its physical structure, strain, or transmutation (in radioactive environments) affect the property measured independent of its temperature.

With a primary thermometer, all the required properties of the sensor are measured and then fed into a fundamental physical law from which true thermodynamic temperature can be calculated.

A Johnson noise level thermometer never needs to be calibrated and is insensitive to the condition of the sensor material, so is ideally suited to long-term temperature measurements in harsh environments. For example, nuclear reactor coolant circuits, nuclear waste management and storage – somewhere you can install your temperature sensor and rely on it for a long time, with no need to replace it regularly.

Also, it is well suited to applications where low drift is required, such as high-temperature reference standards in metrology or the annealing of single-crystal turbine blades in the aerospace industry.

General description of the installation

The Thermocouple Harness comprises of 2 main elements:

1 off Harness & Loom assembly complete with;

• 8 off Thermocouples, fitted with 4 off Thermocouple support clips
• 1 off Integral Analyser loom
• 2 off Integral Analyser loom support clips & bushes

1 off packaging containing;

• 1 off Installation Manual
• 2 off Integral Analyser Loom Supports with spring & plain washers
• 12 off Exhaust Cone Bolts & tab washers
• 1 off Tube of Anti-Seize Compound

NOTE: The Thermocouples have been pre-wired and fitted to the housings. Thus, care should be taken during transit & the subsequent installation to prevent damage.

The procedure for the installation follows:

• Installation of Harness Assembly with Thermocouples
• Installation of Integral loom support clip assembly & multiplug
  • Integral loom support clip assembly (2 off)
  • Multiplug connection (1 off)
• Final electrical inspection.

Please contact us with your requirements.