High Temperature Thermocouples — Most Efficient Technique to Measure the Temprature

Toshniwal Sensors
Jul 27, 2017 · 2 min read

The thermocouple is a very simple and widely used component mostly recommend for measuring the temperature. The thermocouple is described some common challenges that are encountered when designing it, and suggests two signal conditioning solutions for all systems. The high Temperature thermocouples provide solutions that combine with both reference-junction compensation and signal conditioning in a single analog IC for convenience and ease of use. But the second solution separates the reference-junction compensation from the signal conditioning to provide digital-output temperature sensing with greater flexibility and accuracy.

High Temperature thermocouple consists of two wires of dissimilar metals joined together at one end, called the measurement or hot junction. The other end, where the wires are not joined, is connected to the signal conditioning circuitry traces, typically made of copper. This junction established between the thermocouple metals and the copper traces is called the reference or cold junction. The measured junction and the reference junction rather than calling as the traditional hot junction and cold junction. The traditional systems are confusing for measuring the temperature because in many applications the measurement junction can be colder than the reference junction.

The voltage produced by the reference junction depends upon the temperatures at both the measurement junction and the reference junction. Since the high temperature thermocouple is referred to be a different device rather than an absolute temperature measurement device. So, the reference junction temperature must be known to get an accurate absolute temperature reading as a reference junction compensation. Thermocouple become used as a industry-standard method for performing the cost-effective measurement of a wide range of temperatures with reasonable accuracy. They are used in a variety of applications such as boilers, water heaters, ovens, and aircraft engines — to name just a few. The reason behind to use the higher temperature thermocouples are:-

Temperature range: Most practical temperature ranges, from cryogenics to jet-engine exhaust, can be served using thermocouples. Depending on the metal wires used, a thermocouple is capable of measuring temperature in the range –200°C to +2500°C.

Robust: Thermocouples are rugged devices that are mostly useful for immune to moderate shock and vibration and are also suitable for use in hazardous environments.

Rapid response: They are small and have the lowest thermal capacity, thermocouples respond rapidly to temperature changes, especially if the sensing junction is exposed. They can respond very rapidly with the changing temperatures within a few hundred milliseconds.

No self heating: Thermocouples never require any excitation power. So, they are not prone to self heating and are intrinsically safe.

The high Temperature thermocouples offer a robust temperature measurement facility over a quite wide temperature range, but they are frequently not a first choice for temperature measurement because of the required trade offs between design time and accuracy. The first solution concentrates on reducing the complexity of the measurement by means of a hardware-based analog reference junction compensation technique. It defines the results in a straightforward signal chain with no software programming required. The second solution provides the highest accuracy measurement and also enables the use of various thermocouple types.

Toshniwal Sensors

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Toshniwal Sensors Private Limited was incorporated in Ajmer (Rajasthan) in India in 1982. It became a leading manufacturer and supplier of variety of Temperatur

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