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Choosing the right temperature sensor

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Temperature is undoubtedly the most commonly measured physical parameter and has been, in time immemorial. Undoubtedly, our ancestors, just like us today, took a keen interest in the weather and air temperature.

After all, who wants to go out hunting on a freezing cold day?

However, in contrast to the weather temperature, sensing the temperature of your process heat is much more critical. This makes it the most important factor in any thermal loop system.

Choosing the correct temperature sensor depends on several factors. These include; application factors, type of controller being used, the required accuracy and of course, budgets.

Pneu Therm offers a whole range of temperature sensors. These include contact sensors that can be set up to touch the element or included in the medium around the element, if this is what needs to be measured.

There are three main types of temperature sensors – thermocouples, thermistors and Resistant Temperature Detectors (RTD’s). Each of them designed to achieve the same purpose. To collect temperature information from a specific source – depending on the application – and convert this into a readable form.

Thermocouples, the most common temperature sensor, consists of two wires of different metals, welded together into a junction. Heating the sensing junction generates a thermoelectric effect – the conversion of a temperature difference into electrical power, that can then be calibrated according to the application.

There are different types of Thermocouples (type J, T, K etc.), depending on the conducting material and are all extremely rugged and low cost. However, it is imperative to choose the correct thermocouple as this will have an impact on both the range and the accuracy.

We can also supply OEM Replacement Thermocouples, all manufactured to the Original Equipment Manufacturer’s specifications.

Resistant Temperature Detectors (RTD), on the other hand, provide excellent accuracy over a wide temperature range, –200C to 650°C. Consisting of a wired coil or deposited film of pure metal, usually platinum, one of its key features is that the element’s resistance increases with temperature in a known and repeatable manner.

Thermistors although having a higher sensitivity than RTD’s, differ in, that unlike RTD’s, that use pure metals, thermistors are manufactured using a ceramic or polymer material.  The temperature response is also different. RTD’s are ideal for larger temperature ranges while thermistors achieve greater precision with a limited temperature range, typically −90 °C to 130 °C

Also, Thermistors are generally less expensive than both thermocouples or RTD’s.

For more information about choosing the right temperature sensor, please contact us on 01636 679415 or email info@pneutherm.com