Based on the industry standards some combinations of alloys have become popular. Erected on the type of blend the cost convenience, availability, stability chemical properties, melting point and output thermocouples are available. Various types of thermocouples are used in various applications. Individuals have carefully chosen the thermocouple on the base of sensitivity and temperature range. Minimal sensitivity in the thermocouples is observed that has low resolution. We need to check the other factor that is chemical inertness of the thermocouple material.
Nickel alloy thermocouple:
The nickel alloy thermocouple is divided into six types. They are:
Type E, Type J, Type K, Type M, Type N, Type T.
Type E is the combination of chromel and constantan. This type provides a high output of 68µV/°C. It is suitable for Cryogenic purpose. Apart from it is a non-magnetic type material. The narrow range is from −110 °C to +140 °C and the wide ranges from −50 °C to +740 °CAdvertisement:
Type J is the combination of Iron and constantan. This type provides a more restricted range of (−40 °C to +750 °C). Higher sensitivity ranges from 50 µV/°C. Due to Curie point of iron it reasons smooth fluctuations in the appearances. So it is possible to determine the upper limit of the temperature.
Type K is the combination of Chromel and alumel. Type k is the most accepted type of thermocouple with reactivity of about 41 µV/°C. In the Type K wide variety of probes are available in different ranges.
Type M is the combination of Nickel/Molybdenum 82%/18% – Nickel/Copper 99.2%/0.8% in weight. M type is used in vacuum furnaces. Upper limit of the temperature is 1400C. Compared with the other it is less.Advertisement:
Type N is the combination of Nicrosil – Nisil. These types of thermocouples are suitable for ranges between -270 C to + 1330 C unsettled its stability and oxidation resistance. The sensitivity of the thermometer is above 39 µV/°C at 900 °C,compared to K types it is slight lower.
Type N is the combination of copper and constantan. T type is suitable to measure the temperature from -200 C to 350 C. In this process copper wire must touches the probe.
Platinum/rhodium alloy thermocouple:
There are three types of platinum/rhodium alloy thermocouples, they are:
Type B, Type R, Type S.
Tungsten/rhenium alloy thermocouple
There are three types of thermocouple. They are
Type C, Type D, Type G
There is some more type of thermocouple. They are
- Chromel – gold/iron alloy thermocouple
- Type P (noble metal alloy)
- Platinum/molybdenum alloy thermocouple
- Iridium/rhodium alloy thermocouple
- Pure noble metal thermocouple
Applications of Thermocouple:
The thermocouples are suitable for measuring a large temperature ranges. The higher range of the temperature is 2300C.
By using the thermocouple, we can measure the gas turbine exhaust, kilns, diesel engines and fog machines. They are suitable for lesser applications, but the smaller range of temperatures is measured accurately. For the small measurement application the devices use are silicon bandgap temperature sensor, thermistor and resistance thermometers are suitable.
Thermocouples of Type B, Type S, Type R and Type K are extensively used in the iron and steel industries to screen the temperature and chemical process of steel making. The disposals are placed under Type S thermocouples, the thermocouples are normally used in the electric arc furnace process, to obtain accurate dimension of the temperature of the steel earlier to tapping. Here in the cooling curve pick-up, the sample steel piece is used to estimate the carbon content of the molten metal.
Thermocouples are used in:
Gas Appliance safety
Thermopile radiation sensors
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