The Development of an Industrial Primary (Johnson Noise) Thermometer

This project aims to develop a fundamentally different type of thermometer (based on the measurement of Johnson noise) that will not drift. Conventional thermometers are "secondary thermometers" in which a property is measured that is affected by temperature, for example most digital thermometers measure either the resistance of or the voltage produced by the sensor. However, the property measured can be affected by other things so these thermometers drift as they age. This new thermometer is a "primary thermometer" in which the parameters measured are linked directly to temperature by a fundamental physical law, which does not change with time. The phenomenon has been known for a long time, but the signals involved are so small that it has not, so far, been possible to make these measurements reliably in a typical industrial environment. A new approach to measuring Johnson noise will be employed that overcomes the problems that have so far prevented this technique from being used to measure temperature in industrial applications. A successful, commercial Johnson noise thermometer is expected to capture a significant share of the high-performance segment of the industrial temperature measurement market.