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Thermocouple Wire Specifications and Tolerances

Calibration Standard Calibration Points ºF 1
SERV-RITE® Thermocouple Wire Standard Calibration Temperatures
E
J
K
N
T
300, 500, 1000, 1600
200, 500, 1000, 1400
300, 500, 1000, 1600, 2000
300, 500, 1000, 1600, 2000
200, 500
SERV-RITE® Extension Wire Standard Calibration Temperatures
BX
CX
EX
JX
KX
212, 400
200, 300, 400, 500
200, 400
200, 400
200, 300, 400
NX
RX
SX
TX
200, 300, 400
400
400
200, 400
XACTPAK® Calibration Temperatures
B
E
J
K
1600, 2000, 22002, 27002
300, 500, 1000, 1600
200, 500, 1000, 1500
300, 500, 1000, 1600, 20002, 22002
N
R
S
T
300, 500, 1000, 1600, 20002, 22002
1000, 1500, 2000, 27002
1000, 1500, 2000, 27002
200, 500
1 Calibration not made when temperature exceeds wire insulation rating.
2 These calibration temperatures are checked if the sheath and insulation are rated to this temperature.

Initial Calibration Tolerances for SERV-RITE Wire And Cable Reference Junction 0°C (32°F)

Calibration Type Temperature Range Tolerances 1
(whichever is greater)
°C °F Standard Special
Thermocouple Wire Type
B
E
J
K
N
R or S
T
870 to 1700
0 to 900
0 to 750
0 to 1250
0 to 1250
0 to 1450
0 to 350
1598 to 3092
32 to 1652
32 to 1382
32 to 2282
32 to 2282
32 to 2642
32 to 662
±0.5%
±1.7ºC or ±0.5%
±2.2ºC or ±0.75%
±2.2ºC or ±0.75%
±2.2ºC or ±0.75%
±1.5ºC or ±0.25%
±1.0ºC or ±0.75%
 
±1.0ºC or ±0.4%
±1.1ºC or ±0.4%
±1.1ºC or ±0.4%
±1.1ºC or ±0.4%
±0.6ºC or ±0.1%
±0.5ºC or ±0.4%
Extension Wire Type
EX
JX
KX
NX
TX
0 to 200
0 to 200
0 to 200
0 to 200
0 to 100
32 to 392
32 to 392
32 to 392
32 to 392
32 to 212
±1.7ºC
±2.2ºC
±2.2ºC
±2.2ºC
±1.0ºC
±1.0ºC
±1.1ºC
±1.1ºC
±1.1ºC
±0.5ºC
Compensating Extension Wire Type
BX 2
CX 3
RX, SX 4
0 to 200
0 to 870
0 to 200
32 to 392 5
32 to 1600 5
32 to 392 5
±3.7ºC
±6.8ºC
±5ºC
 
Cryogenic Range Wire Type
E 6
K 6
T 6
-200 to 0
-200 to 0
-200 to 0
-328 to 32
-328 to 32
-328 to 32
±1.7ºC or ±1%
±2.2ºC or ±2%
±1.0ºC or ±1.5%
7
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  1. Where tolerances are given in percent, the percentage applies to the temperature being measured in degrees Celsius. For example, the standard tolerance of Type J over the temperature range 277 to 750ºC is ± 0.75 percent. If the temperature being measured is 538ºC, the tolerance is ± 0.75 percent of 538ºC, or ± 4.0ºC. To determine the tolerance in degrees Fahrenheit, multiply the tolerance in degrees Celsius times 1.8.
  2. Copper versus copper compensating extension wire, usable to 100ºC (212ºF) with maximum deviations as indicated, but with no significant deviation over 32 to 0 to 50ºC (122ºF) range. Matched proprietary alloy compensating wire is available for use over the range 0 to 200ºC (32 to 392ºF) with tolerances of ±0.033 mV (±3.7ºC5).
  3. Not an ANSI symbol.
  4. Copper (+) versus copper nickel alloy (-).
  5. Due to the non-linearity of the Types B, C R and S temperature-EMF curves, the error introduced into a thermocouple system by the compensating wire will be variable when expressed in degrees. The degree C tolerances given are based on the following measuring junction temperatures:

    Type Wire Measuring Junction Temperature

    • BX Greater than 1000ºC (1832ºF)
    • SX Greater than 870ºC (1598ºF)
  6. Thermocouples and thermocouple material are normally supplied to meet the tolerances specified in the table for the normal specified range. The same materials, however, may not fall within the cryogenic tolerances in the second section of the table. If materials are required to meet the cryogenic tolerances, the purchase order must so state. Selection of materials usually will be required. Tolerances indicated in this table are not necessarily an indication of the accuracy of temperature measurements in use after initial heating of the materials.
  7. Little information is available to justify establishing special tolerances for cryogenic temperatures. Limited experience suggests the following tolerances for Types E and T thermocouples:
    • Type E -200 to 0ºC ±1.0ºC or ±0.5% (whichever is greater)
    • Type T -200 to 0ºC ±0.5ºC or ±0.8% (whichever is greater)

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These tolerances are given only as guide for discussion between purchaser and supplier. Due to the characteristics of the materials, cryogenic tolerances for Type J thermocouples and special cryogenic tolerances for Type K thermocouples are not listed.