S type thermocouple is one of the many type thermocouple, has been widely applied in industry, electronics, machine tools, ships, water conservancy, oil and other industries as a summary. Users in the use of s type thermocouple for its characteristic is to have a certain understanding, so that in the process of use is more convenient. The characteristics of s type thermocouple s type thermocouple wire winding resistance by special processing, close to face in the thermometer. It compared with general axial thermocouple temperature sensor, can more accurately and quickly to reflect the actual temperature of end face, is suitable for measuring temperature bearing and other parts of the face. S type thermocouple through the special structure of the junction box, the shell internal explosive mixed gas by affected by sparks or electric arc explosion limit within the junction box, that wouldn't make production field explosion. Flameproof thermocouple temperature sensor can be used in the bla level ~ b3c zone with explosion danger place temperature measurement. S type thermocouple temperature sensor is commonly used thermocouple temperature sensing element of the structure. From the temperature sensor of thermocouple temperature measurement principle, the measured the change in temperature is directly measured by the change of the thermocouple temperature sensor resistance, therefore, the wires of a thermocouple temperature sensor body such as a variety of wire resistance change will affect temperature measurement. As to eliminate the influence of the lead resistance with the three wire or four wire system. S type thermocouple thermoelectric potential size is related to temperature and electrode materials with nodes. In order to ensure that the thermoelectric potential with the single function of the temperature, must keep a node temperature is constant. Indexing table and according to the indexing table of thermocouple thermometer calibration are formulated by the reference side of 0 oc, if reference end to not constant, the eab ( t,to) Will change with the change. S type thermocouple is easy to copy, the craft simple, the price is cheap. It is difficult to fully meet the above requirements in practical use. Generally, pure metal is easy to copy, but small thermoelectric potential, an average of 20? V/oc, non-metallic electrode 1000? V/oc, but the replication and poor stability. Usually alloy material is suitable.