Reasons for temperature fluctuations in three-wire thermistors
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There are fluctuations in the three-wire thermistor; each time such fluctuations occur, it takes several minutes to identify the cause. The problem persists even after changing the temperature settings. Please gather all possible causes of these fluctuations so that I can refer to them.
Should it be entered into the DCS or as a separate table? It can’t just be referred to as a thermal resistor
Interference? Measure the resistance before inserting the card to check if there are any fluctuations? Is the temperature of the process medium fluctuating?
On-site terminal blocks can become loose or oxidized due to factors such as temperature differences, vibration, and corrosive gases, which in turn causes changes in contact resistance. The wiring inside the control room also needs to be checked to ensure it is secure and that the contact resistance has not increased. We have used Weidmüller terminals with fuses in the past, the kind that feature external magnetic rings; over time, an increase in resistance to varying degrees was observed, which affected the measurement results.
Check the sleeve surrounding the pipe to see if there is any leakage. Is the thermistor in good contact with the sleeve? Did you replace the temperature conversion module inside the junction box? Pull out the entire resistor and try replacing it
You can use a mechanical watch to test it; if there are no problems, it might be an issue with the gauge or the wiring
Generally, it’s a wiring issue; the main thing to check is whether there are any loose connections in the circuit. In the case of those simple transmitters with small potentiometers used to adjust the zero point and range, it’s necessary to eliminate vibrations
1. First, check the temperature of the process medium to see if it is fluctuating. 2. Eliminate fluctuations in medium temperature by measuring the thermal resistor before the card is inserted to check for any variations. 3. If there is no fluctuation, disconnect the terminal blocks one by one and measure to check for any fluctuations. In any case, once the fault point is identified, it should be easier to handle
First, determine whether there are fluctuations in the process, then check for water stains at the connection terminals, as well as for any electromagnetic interference. Also, consider whether the failure of the thermal resistor is due to poor performance of that resistor............