What are the common faults of thermal resistance elements in use?

Thermistor temperature measurement system generally consists of thermal resistor, connecting wire and display instrument.
The following two points must be noted during use:
(1) The thermal resistor and the display instrument must have the same graduation number. In the DCS system I/0 configuration, the graduation number should also be set.
(2) Try to eliminate the influence of the change in the resistance of the connecting wire. When there is no problem with the thermal resistor itself, as long as you carefully observe the work site and the change in the indication, you can find the cause of the fault. It sounds simple, but it takes some effort to deal with the problem. When a problem occurs, a corresponding indication scale is indispensable. The first thing to do is to determine the temperature at the work site through the scale. Because this is the dividing line between the thermal resistor element and the display instrument, it can directly distinguish which main surface of the primary element, secondary instrument and circuit has a problem.
In use, the thermal resistor will indicate low in some places, but normal in other places. Many people think that the thermal resistor is broken. In fact, this is a manifestation of lack of practical experience. For example, a similar fault occurred in the outlet temperature measurement of the boiler coal mill in our factory, which was caused by a very small sand hole at the end of the protective sleeve. Because there is negative pressure in the pipeline, cold air will be sucked in from the sand hole, resulting in a low measurement value. The solution is to replace a sleeve with good sealing, which not only saves money but also solves the problem.
As a common temperature sensor, thermal resistors are widely used in various industrial fields. Because of its simple principle, it is not taken seriously. When problems occur, people are often confused and directly replace thermal resistors to deal with them.
What are the four common fault problems of thermal resistors?
Thermal resistors are a commonly used temperature measuring instrument with a wide range of applications. All instruments will have certain faults during use, and thermal resistors are no exception. Thermal resistors will also have certain problems when they are used.
1. Fault phenomenon: The display instrument indicates a negative value; Possible cause: The display instrument and the thermal resistor are connected incorrectly or the thermal resistor has a short circuit; Treatment method: Correct the wiring, or find the short circuit, and strengthen the insulation.
2. Fault phenomenon: The indication of the thermal resistor is infinite; Possible cause: The thermal resistor or lead wire is short-circuited or the terminal is loose; Treatment method: Replace the resistor body or weld and tighten the terminal screws, etc.
3. Fault phenomenon: The indication value of the thermal resistor is lower than the actual value or the indication value is unstable; Possible cause: There are metal chips, dust in the protective tube, dirt between the terminals and the thermal resistor is short-circuited; Treatment method: Remove metal chips, clean dust, water droplets, etc., find the short-circuit point and strengthen insulation.
4. Fault phenomenon: The relationship between the thermal resistor value and temperature has changed; Possible cause: The thermal resistor wire material is corroded and deteriorated; Treatment method: Replace the thermal resistor.