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ANSI Letter designations
Thermocouple and extension wires are generally ordered and specified
by ANSI letter designations for wire type. Positive and negative legs are
identified by the appropriate letter suffixes P and N, respectively.
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ANSI
Letter
|
Description
|
Popular
Generic and
Trade Names*
|
|
B
|
BP
|
Platinum 30% Rhodium
|
|
BN
|
Platinum 6% Rhodium
|
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E
|
EP
|
Chromel, Tophel, HAI-KP
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EN
|
Constantan, Cupron, Advance
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J
|
JP
|
Iron
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JN
|
Constantan, Cupron, Advance
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K
|
KP
|
Chromel, Tophel, HAI-KP
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KN
|
Alumel, Nial, HAI-KN
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|
N
|
NP
|
Nicrosil
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NN
|
Nisil
|
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R
|
RP
|
Platinum 13% Rhodium
|
|
RN
|
Pure Platinum
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S
|
SP
|
Platinum 10% Rhodium
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SN
|
Pure Platinum
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T
|
TP
|
Copper
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TN
|
Constantan, Cupron, Advance
|
* Trade names: Cupron, Nial
and Tophel--Carpenter Technology
Advance, HAI-KP, and
HAI-KN-Harrison alloys Co. Chromel and
Alumel- Hoskins Mfg. Co.
Initial Calibration Tolerances
For Thermocouple Extension Wires
| Reference
Junction 0ºC (32ºF) |
Extension
Wire
Type |
Temperature
Range |
Tolerances |
| (ºC) |
(ºF) |
Standard
(ºC) |
Special
(ºC) |
| EX |
0-200 |
32-392 |
±1.7 |
±1.0 |
| JX |
0-200 |
32-392 |
±2.2 |
±1.1 |
| KX |
0-200 |
32-392 |
±2.2 |
±1.1 |
| NX |
0-200 |
32-392 |
±2.2 |
±1.1 |
| TX |
0-100 |
32-212 |
±1.0 |
±0.5 |
Initial Calibration Tolerances
For Thermocouple Extension Wires
| Reference
Junction 0ºC (32ºF) |
Thermo-
couple
Type |
Compen-
sating
Wire Type |
Temperature
Range |
Tolerances^ |
| (ºC) |
(ºF) |
(ºC) |
(ºF) |
| R, S |
SX* |
0-200 |
32-392 |
±7 |
±12 |
| B |
BX# |
0-100 |
32-212 |
+0,-3.7 |
+32,-6 |
^ Due to the
non-linearity of the types R, S, and B 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 are based on
the following measuring junction temperatures.
| Type Wire |
Measuring Junction
Temperature |
| SX |
Greater than 870ºC
(1598ºF) |
| BX |
Greater than 1000ºC
(1832ºF) |
* Copper (+) versus copper
nickel alloy (-).
# Copper versus copper compensating extension
wire, usable to 100ºC (212ºF) with maximum deviations as indicated, but
with no significant deviation over 0ºC to 50ºC (32ºF to 122ºF) range.
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ANSI Tolerances
All thermocouple wire and extension wire is supplied to meet Standard
Tolerances of ANSI Circular MC96.1--1982. Special
tolerances are also available per ANSI MC96.1 at an extra charge. The standard
and special tolerances for thermocouple and extension wires are given in the
accompanying tables. Where tolerances are given in percent, the percentage
applies to the temperature being measured.
Initial Calibration Tolerances for Thermocouples
|
Reference Junction 0ºC (32ºF)
|
|
Thermocouple
Type
|
Temperature
Range |
Tolerances*
(whichever is greater) |
|
(ºC)
|
(ºF)
|
Standard
|
Special
|
|
B
|
870-1700
|
1598-3092
|
± 0.5%
|
--
|
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E
|
0-900
|
32-1652
|
±1.7ºC or
± 0.5%
|
±1.1ºC or
± 0.4%
|
|
J
|
0-750
|
32-1382
|
±2.2ºC or
± 0.75%
|
±1.1ºC or
± 0.4%
|
|
K
|
0-1250
|
32-2282
|
±2.2ºC or
± 0.75%
|
±1.1ºC or
± 0.4%
|
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N
|
0-1250
|
32-2282
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±2.2ºC or
± 0.75%
|
±1.1ºC or
± 0.4%
|
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R or S
|
0-1450
|
32-2642
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±1.5ºC or
± 0.25%
|
±0.6ºC or
± 0.1%
|
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T
|
0-350
|
32-662
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±1.0ºC or
± 0.75%
|
±0.5ºC or
± 0.4%
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*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 277ºC to 750ºC is ±0.75 percent. If the temperature being
measured is 538ºC, the tolerance is ±0.75 percent of 538, or ±4.0ºC. To
determine the tolerance in ºF: Multiply the tolerance in ºC by 9 and divide by
5.
Calibration and Certification
Thermocouple wire and elements can be factory calibrated and
certified at an extra charge. Each thermocouple, coil, reel, or spool of wire is
then tagged to show the individual departure from curve.
The normal calibrating temperature range is 32ºF--2000ºF (0ºC--1093ºC),
depending on wire type, gauge size and insulation type.
A certificate of calibration is furnished for all calibrated items upon request.
Each item calibrated is also tagged with the results.
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