Thermocouple Wire Data

JM_Wire_200x200

THERMOCOUPLE WIRE DATA

Since 1817, Johnson Matthey has been a leader in the recovery, processing and fabrication of precious metals.  Our research and development resources have been intrumental in setting many of today's industrial stnadards.

Serving a large and diverse customer base, Johnson Matthey fabricates products for Platinum Group Metal and their alloys, including wire, tubing, woven gauze meshes, thermocouple wire, laboratory apparatus, sheet and specialty fabrication items.

THERMOCOUPLE WIRE

To meet the need for providing greater reliability in industrial applications, Johnson Matthey manufactures two grades of Platinum and Platinum-Rhodium thermocouple wire: Standard and Special.  Both are processed to the required standards of purity and dimensional accuracy so as to assure proper temperature measurements.

ISA types R & S thermocouples match the emf values listed in the NBS Monograph 125 and in ASTM Standard E230 (prepared in accordance with IPTS-1968) within the following limits at temperatures above 1000°F.

Standard
Grade: ±0.25%
Special Grade: ±0.10%

ISA Types R & S thermocouples are not normally used below 1000°F.  However, for such applications, the deviations in emf values represent no more the 2.5°F for Standard Grade or 1°F for Special Grade.

Platinum - 10% rhodium vs platinum and platinum - 13% rhodium vs platinum thermocouples prepared in accordance with IPTS-1948 are no longer recognized by ISA as letter-designated standard types.  However, when specifically ordered, such thermocouples match the emf values listed in the National Bureau of Standards Circular no. 561 within the following limits at temperatures above 1000°F.

Standard Grade: ±0.25%
Special Grade: ±0.10%

ISA Type B Thermocouples match the emf values listed in the NBS Monograph 125 and ASTM Standard E230 (IPTS-1968) and also NBS.  Vol 70C No. 2 (IPTS-1948).  This is within ±25% in excess of 1600°F (870°C) for Special Grade and within ±50% in excess of 1600°F for Standard Grade.

Wire diameter is uniform within the limits of +0.0000" and -0.0002".  All wire is annealed, cleaned and checked to assure smooth, bright surfaces free of slivers, crack, dirt and other imperfections that could impair its life, or cause improper functioning.

EXCLUSIVE PACKAGING

Thermocouple wire is packaged to assure maxium protection during shipping and handling as well as to simplify thermocouple construction.  It is wound on plastic spools, with each spool encased in a transparent plastic container.  The spool is color coded to indicate basic types as follows:

Black: Pure platinum
Yellow: Platinum-6% rhodium
Maroon: Platinum-10% rhodium
Green: Platinum-13% rhodium
Red: Platinum-30% rhodium

Each label shows composition and diameter as well as gross, tare and net weights.


THERMOELEMENTS TO MEET NBS MONOGRAPH 125 AND ASTM E230 IN ACCORDANCE WITH IPTS-1968 (Recommended Specifications)

Standard Grade Special Grade
PLATINUM (ISA Types SN and RN)
Physical Properties
Tensile Strength (annealed) 24,000 psi 24,000 psi
Elongation - 2" length (annealed) 30% 30%
Electrical Properties
Calibration - when compared with
Platinum 67 at 1200°C the
thermocouple will develop +9 to +19 Microvolts -2 to +9 Microvolts
Homogenity - any two points
in the length of wire when
heated to 1200°C must be
uniform within 6 Microvolts 4 Microvolts
emf change - when heated at
1450°C for prolonged period 8 Microvolts 3 Microvolts
TOR (0-100 C) min 0.00391 0.003923
Purity (Nominal) 99.99+% 99.999+%
PLATINUM-6% RHODIUM (ISA Type BN)
Physical Properties
Tensile Strength (annealed) 40,000 psi 40,000 psi
Elongation - 2" length (annealed) 30% 30%
Electrical Properties +.050 +.025
Calibration - at 1200°C the 6.783 6.783
thermocouple will develop -.050 Millivolts -.025 Millivolts
Homogenity - any two points
in the length of wire when
heated to 1200°C must be
uniform within 6 Microvolts 6 Microvolts
emf change - when heated at
1450°C for prolonged period 10 Microvolts 5 Microvolts
Purity (Nominal) 99.99+% 99.999+%
PLATINUM-10% RHODIUM (ISA Type SP)
Physical Properties
Tensile Strength (annealed) 46,000 psi 46,000 psi
Elongation - 2" length (annealed) 30% 30%
Electrical Properties
Calibration - when heated to +.034 +.012
1200 C vs Platinum 67, the 11.947 11.947
thermocouple will develop -.006 Millivolts -.005 Millivolts
Homogenity - any two points
in the length of wire when
heated to 1200°C must be
uniform within 6 Microvolts 4 Microvolts
emf change - when heated at
1450°C for prolonged period 10 Microvolts 5 Microvolts
Purity (Nominal) 99.99+% 99.999+%
PLATINUM-13% RHODIUM (ISA Type RP)
Physical Properties
Tensile Strength (annealed) 46,000 psi 46,000 psi
Elongation - 2" length (annealed) 30% 30%
Electrical Properties
Calibration - when heated to +.034 +.012
1200 C vs Platinum 67, the 13.224 13.224
thermocouple will develop -.006 Millivolts -.005 Millivolts
Homogenity - any two points
in the length of wire when
heated to 1200°C must be
uniform within 6 Microvolts 6 Microvolts
emf change - when heated at
1450°C for prolonged period 10 Microvolts 5 Microvolts
Purity (Nominal) 99.99+% 99.999+%
PLATINUM-30% RHODIUM (ISA Type BN)
Physical Properties
Tensile Strength (annealed) 70,000 psi 70,000 psi
Elongation - 2" length (annealed) 30% 30%
Electrical Properties +.050 +.025
Calibration - at 1200°C the 6.783 6.783
thermocouple will develop -.050 Millivolts -.025 Millivolts
Homogenity - any two points
in the length of wire when
heated to 1200°C must be
uniform within 6 Microvolts 6 Microvolts
emf change - when heated at
1450°C for prolonged period 10 Mirocvolts 5 Microvolts
Purity (Nominal) 99.99+% 99.999+%

THERMOELEMENTS TO MEET NBS 561 in Accordance with IPTS-1948 (Obsolescent Specifications)

Standard Grade Special Grade
PLATINUM
Physical Properties
Tensile Strength (annealed) 24,000 psi 24,000 psi
Elongation - 2" length (annealed) 30% 30%
Electrical Properties
Calibration - when compared with
Platinum 27 at 1200°C the
thermocouple will develop 0 to +10 Microvolts -10 to +0 Microvolts
Homogenity - any two points
in the length of wire when
heated to 1200°C must be
uniform within 6 Microvolts 4 Microvolts
emf change - when heated at
1450°C for prolonged period 8 Microvolts 3 Microvolts
TOR (0-100 C) min 0.00391 0.003923
Purity (Nominal) 99.99+% 99.999+%
PLATINUM-6% RHODIUM
Physical Properties
Tensile Strength (annealed) 40,000 psi
Elongation - 2" length (annealed) 30%
Electrical Properties +.050
Calibration - at 1200°C the 6.800
thermocouple will develop -.050 Millivolts
Homogenity - any two points
in the length of wire when
heated to 1200°C must be
uniform within 6 Microvolts
emf change - when heated at
1450°C for prolonged period 10 Microvolts
Purity (Nominal) 99.99+%
PLATINUM-10% RHODIUM
Physical Properties
Tensile Strength (annealed) 46,000 psi 46,000 psi
Elongation - 2" length (annealed) 30% 30%
Electrical Properties
Calibration - when heated to +.025 +.004
1200 C vs Platinum 67, the 11.935 11.935
thermocouple will develop -.015 Millivolts -.014 Millivolts
Homogenity - any two points
in the length of wire when
heated to 1200°C must be
uniform within 6 Microvolts 6 Microvolts
emf change - when heated at
1450°C for prolonged period 10 Microvolts 5 Microvolts
Purity (Nominal) 99.99+% 99.999+%
PLATINUM-13% RHODIUM
Physical Properties
Tensile Strength (annealed) 46,000 psi 46,000 psi
Elongation - 2" length (annealed) 30% 30%
Electrical Properties
Calibration - when heated to +.025 +.005
1200 C vs Platinum 67, the 13.103 13.193
thermocouple will develop -.016 Millivolts -.015 Millivolts
Homogenity - any two points
in the length of wire when
heated to 1200°C must be
uniform within 6 Microvolts 6 Microvolts
emf change - when heated at
1450°C for prolonged period 10 Microvolts 5 Microvolts
Purity (Nominal) 99.99+% 99.999+%
PLATINUM-30% RHODIUM
Physical Properties
Tensile Strength (annealed) 70,000 psi
Elongation - 2" length (annealed) 30%
Electrical Properties +.050
Calibration - at 1200°C the 6.800
thermocouple will develop -.050 Millivolts
Homogenity - any two points
in the length of wire when
heated to 1200°C must be
uniform within 6 Microvolts
emf change - when heated at
1450°C for prolonged period 10 Mirocvolts
Purity (Nominal) 99.99+%

CARE AND USE OF PLATINUM-RHODIUM VS. PLATINUM THERMOCOUPLES

Platinum-rhodium vs platinum thermocouples are especiallysuited for use in an oxidizing atmosphere. The commonly used platinum-10% rhodium vs platinum and platinum-13% rhodium vs platinum are recommended for temperatures to 2700°F (1480°C) and, with care, may be used intermittently to 3100°F (1700°C). For extended usage in the range of 2700°F-3100°F, the platinum-30% rhodium vs platinum-6% rhodium thermocouple is recommended.

Because thermocouple wire must be used in the annealed condition for proper response, Johnson Matthey wire is supplied fully annealed in all sizes down to .010-inch diameter, unless otherwise specified. Sizes below .010-inch diameter are normally supplied hard-drawn for east in handling, but are available fully annealed or partially cold-worked on special order.

Thermal EMF of Thermocouples of Alloys in the Platinum-Rhodium System

Thermal_EMG_Graph

Thermocouples can be used bare in clean, oxidizing atmospheres where no forces air flow is present. However, in areas where contaminants and a high rate of air flow are present, servicelife can be increased by the use of insulators and protection tubes. High-purity alumina tubes are recommended for high-temperature applications.

Thermocouples are susceptible to contamination by metallic vapors or other volatile substances such as lead and zinc. The problems of contamination are increased in a reducing atmosphere, especially when silicon or sulfur is present.

Thermocouples that have become superficially contaminated may be cleaned by immersing in either hot hydrochloric acid or fused potassium bisulphate They should then be annealed by electrical resistance at about 1800°F (980°C).

Wire of .020-inch diameter requires a currnet of about 9.5 amperes for performance of the annealing cycle.

The information given herein is based on data which, to the best of our knowledge is reliable, but Johnson Matthey makes no warranties expressed or implied as to its accuracies an assumes no liability.

ISA CLASSIFICATIONS

ISA Classification Material Max. Continuous 0p Temp* Max. Exposure or Short Term 0p Temp**
SP+ Platinum-10% Rhodium 2700 F or 3100 F or
SN- Pure Platinum 1482 C 1704 C
 
RP+ Platinum-13% Rhodium 2700 F or 3100 F or
RN- Pure Platinum 1482 C 1704 C
 
BP+ Platinum-30% Rhodium 3100 F or 3218 F or
BP- Platinum-6% Rhodium 1704 C 1770 C

   *   For protected thermocouples. 24 AWG according to ISA.
   ** For protected thermocouples. 24 AWG short-term exposure without regard to effect on service life.
   Thermocouples exposed to the maximum operating termperature should be examined and calibrated before being used again.

 

Comments are closed