What kind of high temperature thermocouples are available?

Kamet provides various high temperature thermocouple types: S, R, B, C and D. Each thermocouple type has its advantage and can be completely customized to your requirements.  

ThermocoupleTypeSymbolStandard limits of error*Recommended temperature range
+   Per ASTM E 230
Pt10%RhPtSS± 1.5°C or 0.25% per ASTM E 2300-1450°C
Pt13%RhPtRR± 1.5°C or 0.25% per ASTM E 2300-1450°C
Pt30%RhPt6%RhBB± 0.5% per ASTM E 230870-1700°C
W5%ReW26%ReCAE± 4.4°C (0-426°C)
± 1% (426-2315°C per
ASTM E 988)
0-2200°C
W3%ReW25%ReDAO± 4.4°C (0-426°C)
± 1% (426-2315°C per
ASTM E 988)
0-2200°C

What is difference between Type S (Pt10%Rh) and type R (Pt13%Rh) thermocouples? 

Type S and R thermocouples are technically very similar. The only difference is that the positive leg of a Type R consists of 87%Pt, 13%Rh and a Type S of 90%Pt, 10%Rh.  

The main difference between type S and R is the higher percentage of Rhodium in the type R. This makes this thermocouple cable more expensive yet gives a (small) higher output and is overall a bit more stable than the type S. Type S sensitivity is between 6 and 12 µV/°C. Type R has a sensitivity between 6 and 14µV/°C. 

Both type R and type S thermocouples can cover a temperature range of 0°C to 1450°C with uncertainties as good as 0.15°C over most of the range. 

What is the difference between Type C (W5%Re) and Type D (W3%Re) thermocouples? 

The positive leg of a Type C thermocouple consists of 95% Tungsten, 5% Rhenium while the positive leg of a Type D wire consists of 97% Tungsten, 3% Rhenium. The slight difference in output is that the average EMF of Type D is marginally higher than that of Type C.   

It is better to not use Type D thermocouples in temperatures below 500° C.  

Mechanical Properties and Physical Properties

   TungstenW3ReW5ReW25/26 Re
Tensile Strength, ann. (x 103 psi)
8°F
1832°F
3632°F

80
35
15

172
60
10

220
65
26

200
95
24
Elongation (% in 10”)
68°F
1832°F
3632°F

0
10
23

15
18
23

20
24
24

11
19
27
Resistivity (W · circ. mil / ft.)
68°F
1832°F
3632°F

33
199
398

57
228
420

70
235
434

170
331
524
Therm. Exp. Coef. (in./in./°F)
68°F
1832°F
3632°F

1.7×10-6
2.3×10-6
3.1×10-6
  
2.9 x 10-6
3.1 x 10-6
3.9 x 10-6
Density
g./cm3
lb./in3

19.3
0.697

19.4
0.700

19.4
0.701

19.7
0.714
Melting Point
°C
°F

3410
6170

3325
6017

3350
6062

3120
5648