1、 Daily inspection (daily/weekly, quickly identify obvious problems)
Appearance and installation inspection
Check whether the transmitter housing and junction box are damaged or deformed, and whether the waterproof sealing ring of the outlet is aged or cracked, to avoid rainwater and dust infiltration that may cause internal circuit short circuits.
Check whether the installation bracket/threaded joint is loose, whether the probe is in good contact with the measured medium, and confirm that the anti vibration fixture is not detached under vibration conditions.
Running status monitoring
Observe whether the reading on the display screen (if any) is stable, without frequent jumping or over range display; The screenless model can read the output signal (4-20mA/RS485) through a digital display or PLC to confirm that the signal has no drift.
Touch the transmitter housing with your hand and there should be no abnormal heating (normal operating temperature usually does not exceed 60 ℃) to avoid temperature rise caused by circuit faults.
Environmental investigation
Check whether the anti-corrosion coating/sleeve of the probe has peeled off in a corrosive environment; Confirm that insulation measures (such as insulation layers and heat sinks) are intact in high temperature environments.
The installation location should be kept away from strong electromagnetic interference sources (frequency converters, power cables). If the signal fluctuates greatly, it is necessary to check whether the shielding grounding is effective.
2、 Regular maintenance (monthly/quarterly/annual, in-depth maintenance and calibration)
Monthly cleaning and maintenance
Probe cleaning: After disconnecting the power supply, disassemble the probe and use a soft bristled brush or cotton cloth to wipe off any dirt, dust, or oil stains on the surface of the probe; If there are hard attachments, they can be soaked in anhydrous ethanol and gently wiped. It is forbidden to scrape with a metal scraper to avoid damaging the temperature sensing element.
Maintenance of junction box: Open the junction box, clean the internal dust, check whether the wiring terminals are oxidized or loose, and tighten the wiring screws again (with moderate torque to prevent slipping); Replace the aging waterproof gasket and apply a small amount of silicone grease to enhance the sealing performance.
Quarterly sealing test
For explosion-proof and waterproof transmitters, water immersion testing (IP65 or above protection level) or air pressure leak detection can be used to confirm that there is no water or air leakage in the housing.
Check if the gland of the cable inlet is tightened to prevent medium or moisture from seeping into the cable.
Annual precision calibration (core maintenance item)
Calibration prerequisite: Select standard equipment with metrological qualifications (such as precision thermistors and constant temperature troughs), maintain the calibration environment temperature at 20 ± 5 ℃, and avoid environmental temperature affecting the calibration results.
Calibration steps
Place the transmitter probe into a constant temperature bath and set 3 calibration points (usually 0%, 50%, and 100% of the range). Record the transmitter output value after the temperature inside the bath stabilizes.
Compare the output value with the theoretical signal value corresponding to the standard temperature and calculate the error. The allowable error of industrial grade temperature transmitters is usually ≤± 0.2% FS. If it exceeds the tolerance, zero and range corrections can be made through the transmitter's built-in calibration button or software.
After the calibration is completed, record the calibration data and paste the calibration qualified label, specifying the next calibration time.
3、 Troubleshooting and emergency response (in case of abnormalities)
Common faults and solutions
Possible causes and solutions for the fault phenomenon
Output signal: 0mA probe open circuit, loose wiring, power failure check probe circuit on/off; Tighten the wiring terminals; Measure whether the power supply voltage is within the rated range (usually 24VDC)
Troubleshooting probe insulation for short circuits and incorrect range settings when the output signal is above 20mA; Recheck the range parameters; Check for over temperature measurement
Large reading drift/fluctuation, probe contamination, poor grounding, electromagnetic interference cleaning probe; Check if the grounding of the shielded wire is reliable; Stay away from interference sources or install signal isolators
Maintain taboos
It is prohibited to disassemble the junction box or probe while it is live to prevent electric shock or damage to the circuit.
Do not directly flush the transmitter housing with high-temperature steam to avoid aging and failure of the sealing components.
It is prohibited to calibrate beyond the range or modify parameters without the manufacturer's permission to prevent transmitter damage.
4、 Spare parts management
Reserve commonly used accessories (such as waterproof gaskets, wiring terminals, probe protection sleeves), especially for transmitters under harsh working conditions, spare probes of the same model are needed for quick replacement of faulty parts.