In praise of the humble thermocouple
31 January 2019
Labfacility will be showcasing its wide range of temperature Sensors, thermocouple connectors and associated temperature instrumentation on stand E195 at Southern Manufacturing & Electronics 2019. Ahead of the event, the company explores enduring popularity of the uncomplicated thermocouple in today’s high-tech world.
Where does the humble thermocouple stand in the high-tech world of measurement and control? The funny thing is that the temperature instrumentation market is dominated by complex, sophisticated measurement and control systems which provide a high degree of versatility and accuracy but, in many applications rely on a simple thermocouple as the temperature sensor (base-metal type usually). This is surprising really since instrumentation is typically accurate to a fraction of a degree centigrade whereas a base-metal thermocouple has uncertainties of ±2ºC before it even sees the process. Since measurement accuracy of the entire process is only as good as that of the sensor, why rely on something that, in principle, at least, has not significantly changed in nearly 200 years (Thomas Seebeck discovered the principle of the thermocouple in 1821). Why indeed especially when you are presented with a feeble output (typically 40µV/ºC), a non-linear transfer characteristic and the need for automatic “cold-junction” compensation or some external ice reference; also, one of several types must be selected for each application, complete with a dedicated type of extension cable.
The answer to these questions is a surprisingly simple one – nobody has yet been able to come up with anything better to cope with harsh environments and wide temperature ranges.