Characteristics of temperature sensors
From ASHRAE 1997, with permission
Category |
Measurement Means |
Application |
Approximate Range |
Uncertainty |
Limitations |
||
°F |
°C |
°F |
°C |
||||
Liquid-in-glass thermometers |
Mercury-in-glass |
Temperature of gases and liquids by contact |
-36/1000 |
-38/550 |
0.05 to 3.6 |
0.03 to 2 |
In gases, accuracy affected by radiation |
Organic |
Temperature of gases and liquids by contact |
-330/400 |
-200/200 |
0.05 to 3.6 |
0.03 to 2 |
||
Gas thermometer |
Primary standard |
-456/1200 |
-271/665 |
< 0.02 |
< 0.01 | Requires considerable skill to use |
|
Resistance thermometers |
Platinum |
Precision; remote readings; temperature of fluids or solids by contact |
-430/1800 |
-259/1000 |
< 0.0002 to 0.2 |
< 0.0001 to 0.1 | High cost; accuracy affected by radiation in gases |
Rhodium-iron |
Transfer standard for cryogenic applications |
-460/-400 |
-273/-243 |
0.0002 to 0.2 |
0.0001 to 0.1 |
High cost |
|
Nickel |
Remote readings; temperature by contact |
-420/400 |
-250/200 |
0.02 to 2 |
0.01 to 1 |
Accuracy affected by radiation in gases |
|
Germanium |
Remote readings; temperature by contact |
-460/-400 |
-273/-243 |
0.0002 to 0.2 |
0.0001 to 0.1 |
||
Thermistors |
Remote readings; temperature by contact |
Up to 400 |
Up to 200 |
0.0002 to 0.2 |
0.0001 to 0.1 |
||
Category |
Measurement Means |
Application |
Approximate Range |
Uncertainty |
Limitations |
||
°F |
°C |
°F |
°C |
||||
Thermocouples |
Pt-Rh/Pt (type S) |
Standard for thermocouples on IPTS-68, not on ITS-90 |
32/2650 |
0/1450 |
0.2 to 5 |
0.1 to 3 |
High cost |
Au/Pt |
Highly accurate reference thermometer for laboratory applications |
-60/1800 |
-50/1000 |
0.1 to 2 |
0.05 to 1 |
||
Types K and N |
General testing of high temperature; remote rapid readings by direct contact |
Up to 2300 |
Up to 1250 |
0.2 to 18 |
0.1 to 10 |
Less accurate than thermocouples listed above |
|
Iron/Constantan (type J) |
Same as above |
Up to 1400 |
Up to 750 |
0.2 to 10 |
0.1 to 6 |
Subject to oxidation |
|
Copper/Constantan (type T) |
Same as above, especially suited for low temperature |
Up to 660 |
Up to 350 |
0.2 to 5 |
0.1 to 3 |
||
Ni-Cr/Constantan (type E) |
Same as above, especially suited for low temperature |
Up to 1650 |
Up to 900 |
0.2 to 13 |
0.1 to 7 |
||
Beckman thermometers (metastatic) |
For differential temperature in same applications as in glass-stem thermometer |
10°F scale, used 32 to 212°F |
0 to 100 |
0.01 |
0.005 |
Must be set for temperature to be measured |
|
Bimetallic thermometers |
For approximate temperature |
-4/1200 |
-20/660 |
2, usually much more |
1, usually much more |
Time lag; unsuitable for remote use |
|
Category |
Measurement Means |
Application |
Approximate Range |
Uncertainty |
Limitations |
||
°F |
°C |
°F |
°C |
||||
Pressure-bulb thermometers |
Gas-filled bulb |
Remote testing |
-100/1200 |
-75/660 |
4 |
2 |
Caution must be exercised so that installation is correct |
Vapor-filled bulb |
Remote testing | -25/500 |
-5/250 |
||||
Liquid-filled bulb |
Remote testing | -60/2100 |
-50/1150 |
||||
Optical pyrometers |
For intensity of narrow spectral band of high-temperature radiation (remote) |
1500 and up |
800 and up |
30 |
15 |
||
Radiation pyrometers |
For intensity of total high-temperature radiation (remote) |
Any range |
|
|
|||
Seger cones (fusion pyrometers) |
Approximate temperature (within temperature source) |
1200/3600 |
660/2000 |
90 |
50 |
||
Triple points, freezing/melting points, and boiling points of materials |
Standards |
All except extremely high temperature |
Extremely precise |
For laboratory use only |