Tag: thermocouple

Thermocouple is a commonly used temperature measuring element in temperature measurement instruments. It directly measures temperature and converts the temperature signal into a thermoelectric electromotive force signal, which is then converted into the temperature of the measured medium through electrical instruments (secondary instruments). The appearance of various thermocouples is often very different due to needs, but their basic structure is generally the same. They are usually composed of main parts such as thermal electrodes, insulation sleeve protection tubes, and junction boxes, and are usually used in conjunction with display instruments, recording instruments, and electronic regulators.

Thermocouple temperature sensors are characterized by wide range, low cost, fast response and durability. They are widely used for temperature measurement in industry. R-type thermocouples can measure high temperatures of more than 1700 degrees, and are mainly used in high temperature measurement occasions. In today's article, let's talk about how thermocouples work.

Temperature sensor equipped for the temperature transmitter can be divided into thermocouple and RTD, and the RTD sensor can be divided into three kinds of 2-wire RTD, 3-wire RTD and 4-wire RTD. Despite of the differences mentioned above, measurements and principles of the temperature transmitter are the same. Now the indication error calibrating of ATO-S-TEMPT-ST500 temperature transmitter would be taken as example to analyze temperature transmitter calibration and errors in the process.

Industrial thermocouple and RTD protective casing are almost the same. Some temperature measuring elements are small in size, such as the armored type, and they also have similar shape. So, how to identify whether it is RTD or thermocouple without nameplate or unknowing the type? The following methods are listed to figure out the RTD and thermocouple for your reference.

After connecting the wires accurately according to the wiring diagram and powering on, the meter displays the thermocouple graduation firstly and then the range, measure the nixie tube on the lower part of the meter to display the setting temperature, and measure the nixie tube on the upper part of the meter to display the measuring temperature. If the upper nixie tube doesn’t display the temperature of the heating body but the other states such as “OVER”, “0000” or “000”, meaning that the output part of the meter goes wrong, following inspections shall be made:
Remove the thermocouple from the thermocouple output end of the instrument and then short circuit the thermocouple output end of the instrument with a wire. If the temperature showed on the upper nixie tube is close to the room temperature after powering on, meaning that exterior wire connection of the thermocouple disconnects, replace with a same thermocouple. If it keeps a same state as previous, meaning that the output end of the instrument is damaged in transportation, change an instrument please.