Thermocouple Letter Designations - RDC Control - Canadian Thermocouple Manufacturer

1) What do thermocouple letter designations mean?

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Thermocouple Introduction

Thermocouple Types

Thermocouples and Extension Wires

Thermocouples are classified by calibration type because they have differing EMF (electromotive force) versus temperature curves. Some generate considerably more voltage at lower temperatures, while others do not begin to develop a significant voltage until subjected to high temperatures. Also, calibration types are designed to deliver as close to a straight line voltage curve inside their temperature application range as possible. This makes it easier for an instrument or temperature controller to correctly correlate the received voltage to a particular temperature. Additionally, thermocouple calibration types have different levels of compatibility with different atmospheres. Chemical reaction between certain thermocouple alloys and the application atmosphere could cause metallurgy degradation, making another calibration type more suitable for sensor life and accuracy requirements.

ASTM E-230 Letter	Thermoelement Alloys	Minimum & Maximum Temperatue Range
ASTM E-230 Letter	Thermoelement Alloys	°C	°F
B		870 to 1700	1600 to 3100
BP (+)	Pt 30% Rh
BN (-)	Pt 6% Rh
E		-200 to 870	-328 to 1600
EP (+)	Chromel
EN (-)	Constantan
J		0 to 760	32 to 1400
JP (+)	Iron
JN (-)	Constantan
K		-200 to 1260	-328 to 2300
KP (+)	Chromel
KN (-)	Alumel
N		0 to 1260	32 to 2300
NP (+)	Nicrosil
NN (-)	Nisil
R		0 to 1480	32 to 2700
RP (+)	Pt 13% Rh
RN (-)	Pure Pt
S		0 to 1480	32 to 2700
SP (+)	Pt 10% Rh
SN (-)	Pure Pt
T		-200 to 370	-328 to 700
TP (+)	Copper
TN (-)	Constantan

Thermocouple Types
Calibration types have been established by the American Society for Testing and Materials (ASTM) according to their temperature versus EMF characteristics in accordance with ITS-90, in standard or special tolerances.

1) What do thermocouple letter designations mean?

2) What are thermocouple color codes?

3) What letter of calibration should I use?

4) What is the initial accuracy of temperature sensors?

5) Is there a maximum length for thermocouples and thermocouple wiring?

6) What sheath material is the best for my application?

7) What are the maximum temperatures of thermocouples?

8) What type of junction should I use?

9) What is the response time of mineral insulated thermocouples?

10) Where should my sensor be placed?

11) What should the thermocouple resistance measure?

12) The sensor appears to be reading incorrectly. What might be wrong?