Richards Thermocouple and Temperature Sensor Catalog 16

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TYPES

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Extensions - Single Extensions

The Type R thermocouple is composed of Platinum-13% Rhodium (+) wire verses a Platinum (-) wire. This type of thermocouple can be used in oxidizing or inert atmospheres with a service temperature range between 0 and 1480°C (32 to 2700°F). They should never be used in reducing atmospheres. As with all platinum type thermocouples, they should always be protected with a ceramic protection tube. Alumina insulators and protection tubes are preferred to prevent silica contamination from Mullite ceramics. When Type R thermocouples are continuously used at higher tem- peratures, the elements can develop excessive grain growth in time causing mechanical breakage to the thermocou- ple. In most situations platinum thermocouples should not be placed in any type of metal tube or in applications where metallic vapors are present. The Type S thermocouple is composed of Platinum-10% Rhodium (+) wire verses a Platinum (-) wire. This type of thermocouple can be used in oxidizing or inert atmospheres with a service temperature range between 0 and 1480°C (32 to 2700°F). They should never be used in reducing atmospheres. As with all platinum type thermocouples, they should always be protected with a ceramic protection tube. Alumina insulators and protection tubes are preferred to prevent silica contamination from Mullite ceramics. When Type S thermocouples are continuously used at higher tem- peratures, the elements can develop excessive grain growth in time causing mechanical breakage to the thermocou- ple. In most situations platinum thermocouples should not be placed in any type of metal tube or in applications where metallic vapors are present. The Type T thermocouple is composed of a Copper (+) wire verses a Nickel– 45% Copper (-) wire. The Type T thermocouple is frequently referred to as Copper-Constantan. This type of thermocouple can be used in oxidizing, reducing, or inert atmospheres with a service temperature range between -200 and 370°C (-330 to 700°F). The Type T thermocouple is one of the few thermocouples which have established limits of error for use in subzero and cryogenic applications. This is possible due to the Type T’s superior corrosion resistance in moist environments. The Type PK thermocouple (Platinel II 6 ) is composed of a Palladium– 55%, Platinum– 31%, and Gold- 14% (+) wire verses a Palladium– 35%, and Gold- 65% (-) wire. The Type PK thermocouple is a noble- metal form and should be protected in the same manner as a Type B, R, or S. This type of thermocouple was developed to approximate the Type K Curve at higher temperatures. It can be used in oxidizing or inert atmospheres with a service temperature range up to 1260°C (2300°F). When using Type PK ther- mocouples, Type KX extension wire should be used. The Type N thermocouple is composed of a Nickel -14% Chromium - 1 1/2% Silicon (+) wire verses a Nickel – 4 1/2% Silicon - 1/10% Magnesium (-) wire. The Type N thermocouple is the newest addition to the ISA family. This type of thermocouple was developed to be used under the same conditions as a Type K. It should be used in oxidiz- ing or inert atmospheres with a service temperature range between -200 and 1260°C (-330 to 2300°F). The addition of Silicon and Chromium makes this type of thermocouple more resistant to Green-Rot and less drifting when com- pared to a Type K. The negative leg, or NN, of a Type N thermocouple can be described by any of the following names: Nisil, Nickel - Silicon, or HAI-NN 1 . The positive leg, or NP, of a Type N thermocouple can be described by any of the following names: Nicrosil, Nickel - Chromium - Silicon, or HAI-NP 1 .

R S N

T

PK

! Note: The Thermocouple types we describe in this Richards Catalog are the letter designations assigned by the Instrument Society of America (ISA) and adopted in ANSI MC 96.1 and ASTM E 230 with the exception of “PK”. The Type PK is a designation used by us to describe Platinel II 6 . There are other more exotic types of thermocouples, which have been devel- oped, but since they are rarely used we decided not to list them in this catalog. If you have any questions regarding any of these less common types of thermocouples, contact one of our sales engineers and we will be glad to assist you.

1 Trademark of Harrison Alloys. Incorporated 2 Trademark of The Hoskins Manufacturing Company 3 Trademark of Driver Harris Company 4 Trademark of Carpenter Technology Corporation

5 Trademark of Kanthal Corporation 6 Trademark of Engelhard Industries

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