This document discusses thermocouples, which are temperature measuring devices consisting of two dissimilar conductors that produce a voltage when joined and exposed to different temperatures. It describes how thermocouples work using the Seebeck effect. Common types of thermocouples are also outlined, including Type K and Type T thermocouples, along with their temperature ranges, accuracy, and applications. The document highlights the wide temperature range, fast response time, low cost, and durability as advantages of thermocouples, while noting that cold junction compensation and signal amplification may be limitations.

2. Group Members :-
1)Aniket Vinod Bore -13
2)Nayan Dipak Gaykwad - 23

3. TEMPERATURE MEASURING DEVICE
THERMOCOUPLE

4. THERMOCOUPLE :-
 A Thermocouple is a temperature measuring device consisting of two
dissimilar conductors that contact each other at one or more spots.
 A Thermocouple is a sensor made from two dissimilar metals. When these
two metals are fused together at one end they create a junction.
 When the junction experiences changes in temperature, a very small voltage
is created .which corresponds to a temperature reading.

5. WORKING PRINCIPLE AND TYPES :-
 Thermocouples operate under the principle that a circuit made by connecting
two dissimilar metals produces a measurable voltage (emf-electromotive
force) when a temperature gradient is imposed between one end and the other.
 The EMF generated by the Seebeck effect is due to the temperature gradient
along the wire. The EMF is not generated at the junction between two
dissimilar wires.
 TYPES OF COUPLES.
o Type K
o Type J
o Type T

6. Measuring Temperature :-
• To measure temperature using a thermocouple, you can’t just connect the
thermocouple to a measurement system (e.g. voltmeter)
• The voltage measured by your system is proportional to the temperature
difference between the primary junction (hot junction) and the junction where
the voltage is being measured (Ref junction)
You need to know
the temperature at
the Ref junction!
To determine
the absolute
temperature at
the hot
junction…

7. TYPE T
• copper (+) | constantan (-) | is a very stable thermocouple at low temperature
ranges.
• This type is most often used in low temperature applications including frozen
foods and cryogenics.
Temperature Range:
• Thermocouple grade wire, -452 to 700°F (-269 to 371°C)
• Extension grade wire, 32 to 392°F (0 to 200°C)
Accuracy (whichever is greater):
• Standard: +/- 2.2°C or +/- .75%
• Special Limits of Error: +/- 1.1°C or 0.4

8. TYPE K
• chromel (+) | alumel (-) is the most common general purpose thermocouple.
• Type K probes are reliable, inexpensive and has a wide temperature range.
• This is the most versatile sensor type and can hold continuously high
temperatures.
Temperature Range:
• Thermocouple grade wire, -328 to 2,300°F (-200 to 1260°C)
• Extension grade wire, 32 to 392°F (0 to 200°C)
Accuracy (whichever is greater):
• Standard: +/- 2.2°C or +/- .75%
• Special Limits of Error: +/- 1.1°C or 0.4%

9. Applications
1.Steel industry
2.Gas appliance safety
3.Thermopile radiation sensors
4.Manufacturing
5.Power production
6.Thermoelectric cooling
7.Process plants
8.Thermocouple as vacuum gauge (Gas appliance safety )

11. 1.Very wide temperature range (1.2 K to 2300 dig C)
2.Fast response time
3.Available in small sheath sizes
4.Low initial cost
5.Durable.
ADVANTAGES

12. LIMITATIONS
o For accurate temperature measurement, cold junction compensation is
necessary.
o The EMF induced versus temperature characteristics is somewhat non-linear.
o Stray voltage pickup is impossible.
o In many application, amplification of signal is required.

13. THANK YOU.