Sensing RTD elements, Pt100, Pt1000 and more, thermistors and assemblies for industrial and laboratory use and more

How is Temperature Measured?

How is Temperature Measured?

Temperature can be measured via a diverse array of sensors. All of them infer temperature by sensing some change in a physical characteristic. Six types with which the engineer is likely to come into contact are: thermocouples, resistive temperature devices (RTDs Pt100 and thermistors), infrared radiators, bimetallic devices, liquid expansion devices, and change-of-state devices.

Choose the right temperature measurement instrument for your application...


RTD Pt100 vs Thermocouple

RTD Pt100 vs Thermocouple

It is not practical to compare RTDs (Pt100 and others) and thermocouples generally. However, if we compare their performance in terms of specific criteria, we can see which is best suited for specific applications. Thermocouples are best for working at high temperatures. New manufacturing techniques have improved the measurement range of RTD probes, but more than 90% of RTDs are designed for temperatures below 400°C.

In contrast, some thermocouples can be used at up to 2500°C. Thermocouples are generally cheaper than RTDs...


Origin Story of the RTD / Pt100

Origin Story of the RTD / Pt100

The same year (1821) that Thomas Seebeck made his discovery about thermoelectricity (Seebeck effect, see thermocouples), Sir Humphrey Davy announced that the resistivity of metals showed a marked temperature dependence. Fifty years later, Sir William Siemens proffered the use of platinum as the element in a resistance thermometer. His choice proved most propitious, as platinum is used to this day as the primary element in all high-accuracy resistance thermometers, Pt100, Pt1000 etc.

In fact, the Platinum Resistance Temperature Detector, or RTD Pt100, is used today as an interpolation standard from the oxygen point (-182.96°C) to the antimony point (630.74°C)...