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Common Thermocouple TYPes - Types; Bn E, J, K, N, R, S, T, C (WsR) & P (Platinel ll)

The Type R thermocouple is composed of a platinum-13% rhodium (+) wire versus 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 (321o 27OO"F). They should never be used in reducing atmospheres. As with all platinum type thermo- uples, they should always be protected with a ceramic protection tube. Alumina insulators and protection tubes preferred to prevent silica contamination from Mullite ceramics. When Type R thermocouples are continuously used at high temperatures, the elements can develop excessive grain growth in time causing mechanical breakage to the thermocouple. ln 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 a platinum-10% rhodium (+) wire versus 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 1o2700"F). They should never be used in reducing atmospheres. As with all platinum type thermo- couples, 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 continu- ously used at high temperatures, the elements can develop excessive grain growth in time causing mechanical break- age to the thermocouple. ln most situations platinum thermocouples should not be placed in any type of metal tube or The Type T thermocouple is composed of a copper (+) wire versus a nickel-45% copper (-) wire. The Type T thermocouple is frequently referred to as copper-constantan. This type of thermocouple can be used in oxidiz- ing, reducing, or inert atmospheres with a service temperature range between -200 and 370'C (-330 to 700'F). The high temperature use of this thermocouple is also limited due to rapid oxidation of the copper element. The Type T thermocouple is one of the few thermocouples which have established limits of error for use in subzero and cryo- genic applications. This is possible due to the Type T's superior corrosion resistance in moist environments. The Type C or WSR thermocouple is composed of a tungsten-S% rhenium (+) wire versus a tungsten-26"/" rhe- nium (-) wire. This Vpe of thermocouple can be used in high temperature vacuum or ineft atmospheres with a service temperature range up to 2316'C (4200'F). lt has very poor oxidation resistance, which must be taken into consideration. The Type C thermocouple is the most common tungsten-rhenium form of thermocouple due to the conductors being the least brittle at room temperature. This characteristic is very important since brittle con- ductors create inferior thermocouples. thermocouple is composed of a palladium-55%, platinum-31"/", and 14% gold (+) wire versus a65"/" gold and 35% palladium (-) wire. TheType Pthermocouple is a noble-metal form and should be protected in the same manner as a Type R, S, or B. This type of thermocouple was developed to approximate the ype K curve at high temperatures. lt can be used in oxidizing or inert atmospheres with a service temperature to 1260"C (2300"F). When using Type P thermocouples, Type K extension wire should be used. Tyrpe The Type P or Platinel 116 in applications where metallic vapors are present.

Note: The thermocouple types we describe in the Richards Catalog # 15 are the letter designations assigned by the lnstrument Society of America (lSA) and adopted as an American Standard in ANSI MC 96.1. The Type C and P letters are exceptions. The Type C and Type P are letter designations commonly used today by thermocouple manufacturers and not the lSA. There are a few other

more exotic types of thermocouples, which have been developed, but since they are rarely used we decided not to list them in this catalog. lf you have any questions regarding any of these other less common types of thermocouples, contact one of our sales engineers and we will be glad to assist you.

lTrademark of Harrison Alloys, lncorporated. 2Trademark of the Hoskins Manufacturing Company 3Trademark of Driver Harris Company 4Trademark of Carpenter Technology Corporation

STrademark of Kanthal Corporation oTrademark of Engelhard lndustries

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