Thermocouple Working Principle

A thermocouple is a sensor for measuring temperature. This sensing device consists of two dissimilar metal wires, joined at the both side end, and A current is created when the temperature applied to one end or junction differs from the other end. This phenomenon is known as the Seebeck effect, which is the basis for thermocouple temperature measurement. One end is referred to as the hot junction whereas the other end is referred to as the cold junction. The hot junction measuring element is placed inside a sensor sheath and exposed to the process. The cold junction, or the reference junction, is the termination point outside of the process where the temperature  is known and where the voltage is being measured. This cold junction is typically in a transmitter, control system input card or in a signal conditioner. Transmitters accept inputs from most common industry standard T/C types including types J, K, E, T, R, and S. Many models can also accept the types B and C and Type N, which commonly serves as an alternative to Types R and S. Output of thermocouple is millivolt , if transmitted than voltage drop loses and noise pickup and need to convert 4-20 mA current signals transmission to receive signal.

Single thermocouple

Single point thermocouple measurement on single pints in terms of pipe line, vessel , tank or any points.

Dual Thermocouple  

Dual thermocouple are design of thermocouple that has two individual thermocouple sensor in one sheath. Dual sensors is more reliable measurement through sensor redundancy also.

Triplex thermocouples 

Triplex thermocouple is a design of thermocouple that has three individual thermocouple sensors in one sheath and this thermocouple is more reliable as compared with single and dual thermocouple. These types of the instrument used where temperature factor is more critical like reactor and other as per process requirements.

Multi Pont temperature measuring

Multipoint temperature sensor is measuring the temperature at different points along their length and these instruments frequently used in the fertilizer and petrochemical industries reactors, catalytic crackers and fractionation distillation towers or columns and these sensor can be measured at different points for 2 to more than  50  measuring points within single protection tubes that means one sensor measured more than 50 different points , these can be used thermocouple or RTD depend upon range , accuracy

Thermocouple Temp Range

Most commonly used thermocouple is types J, K, E, T, R, and S., Different types and different range

Thermocouple colour code

Thermocouple Wire, Probes and Connectors as per ANSI or IEC color Codes

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