Thermocouple Types and Comparison

Thermocouple types and probes and thermocouple cables used for measurement of temperature, mode of furnace thermocouple working and high temperature thermocouples working procedure, functioning of termistor. Calibration of temperature sensors, material of construction of various thermocouple based on the utilisation, mechanism of fitting the thermocouple to the process equipments and working principle of thermocouple testing. B,E,J,K,R,S,T types of thermocouple comparison



Sr no
Type
Positive wire
Negative wire
Temperature range 0C
Linearity
1
B
Pt-70—Rh-30
Pt-94—Rh-6
0 to 1860
Good at high temperature
2
E
Chromel
Constantan
-196 to 999
Good
3
J
Iron
Constantan
-196 to 760
Nearly linear between 149 to 438
4
K
Chromel
Alumel
-190 to 1371
Most linear
5
R
Pt-87—Rh-13
Platinum
-18 to 1704
Good at high temperature
6
S
Pt-90—Rh-10
Platinum
-18 to 1760
Good at high temperature
7
T
Copper
Constantan
-190 to 399
Same as J
8

Tungsten W
W 74 –Re 26
-18 to 2316
Good at high temperature
9

W 94 –Re 6
W 74 –Re 26
-18 to 2316
Good at high temperature
10

Copper
Gold – Cobalt
-268 to -18
Linear above 60k
11

Ir 40- Rh 60
Ir
-18 to 2093
Good at high temperature

Pt- Platinum
Rh- Rhodium
W- Tungsten
Re- Rhenium
Ir-Iridium
At various corrosive environments the instrument should function and measure the temperature, for that purpose a list of thermocouple will help to determine the right suitable temperature measuring instrument.


Sr no
Type
Positive wire
Negative wire
Suitable atmosphere
1
B
Pt-70—Rh-30
Pt-94—Rh-6
Inert or slow oxidizing
2
E
Chromel
Constantan
Oxidizing
3
J
Iron
Constantan
Reducing
4
K
Chromel
Alumel
Oxidizing
5
R
Pt-87—Rh-13
Platinum
Oxidizing (fast response)
6
S
Pt-90—Rh-10
Platinum
Oxidizing
7
T
Copper
Constantan
Oxidizing or reducing(good corrosion resistance)
8
Y
Iron
Constantan
Reducing
9
--
Tungsten W
W 74 –Re 26
Inert or vacuum(high temperature)