Temperature measurement principle of explosion-proof thermal resistor and thermal resistor

It is based on the characteristic that the resistance value of a conductor or semiconductor changes with temperature to measure temperature and temperature-related parameters. Most thermal resistors are made of pure metal materials. Platinum and copper are currently the most widely used. Now, nickel, manganese and rhodium are used to make thermal resistors. Thermal resistors usually need to transmit resistance signals to computer control devices or other secondary instruments through leads.
Metal thermal resistors are commonly used in industry. From the perspective of the change of resistance with temperature, most metal conductors have this property, but not all of them can be used as temperature measuring thermal resistors. Metal materials used as thermal resistors generally require: as large and stable temperature coefficient as possible, large resistivity (reducing the size of the sensor at the same sensitivity), stable chemical and physical properties within the temperature range of use, good material reproducibility, and resistance value changes with temperature. There should be an intermediate value function relationship (preferably a linear relationship).
Thermal resistors are the most commonly used temperature detectors in medium and low temperature zones. Thermal resistor temperature measurement is based on the characteristic that the resistance value of metal conductors increases with the increase of temperature to measure temperature. Its main features are high measurement accuracy and stable performance. Among them, platinum thermal resistors have the highest measurement accuracy. They are not only widely used in industrial temperature measurement, but also made into standard reference instruments. Most thermal resistors are made of pure metal materials. Currently, platinum and copper are the most widely used. In addition, nickel, manganese and rhodium are now being used to make thermal resistors. There are many types of temperature sensing materials commonly used in metal thermal resistors, and the most commonly used is platinum wire. In addition to platinum wire, metal thermal resistor materials for industrial measurement also include copper, nickel, iron, iron-nickel, etc.
1. In order to ensure sufficient heat exchange between the measuring end of the thermal resistor and the measured medium, the measuring point should be reasonably selected, and try to avoid installing the thermal resistor near valves, elbows, and dead corners of pipelines and equipment.
2. Thermal resistors with protective sleeves have heat transfer and heat dissipation losses. In order to reduce measurement errors, thermocouples and thermal resistors should have sufficient insertion depth:
(1) For thermal resistors that measure the temperature of the fluid in the center of the pipeline, the measuring end should generally be inserted into the center of the pipeline (vertically or tilted). If the diameter of the pipeline of the measured fluid is 200 mm, the insertion depth of the thermal resistor should be 100 mm;
(2) For high temperature and high pressure For the temperature measurement of high-speed fluid (such as main steam temperature), in order to reduce the resistance of the protective sleeve to the fluid and prevent the protective sleeve from breaking under the action of the fluid, the protective tube can be shallowly inserted or a heat sleeve thermal resistor can be used. The shallow insertion thermal resistor protective sleeve should be inserted into the main steam pipe to a depth of not less than 75mm; the standard insertion depth of the heat sleeve thermal resistor is 100mm;
(3) If the temperature of the flue gas in the flue needs to be measured, even if the flue diameter is 4m, the thermal resistor can be inserted to a depth of 1m.
(4) When the insertion depth of the measuring element exceeds 1m, the explosion-proof thermal resistor should be installed vertically as much as possible, or a support frame and protective sleeve should be installed.