I. Evaluation of Signal Anomaly
Uncontrolled Data Jumps: Displacement values fluctuate erratically, with fluctuations exceeding 0.2mm. The issue remains unresolved despite the addition of an isolation barrier and the replacement of the shielded cable. This suggests that the signal acquisition module within the sensor is damaged and necessitates repair.
The 4~20mA analogue output consistently displays 0mA or 20mA, indicating a complete loss of output signal. Normal signal output is not displayed by a multimeter. The sensor hardware is determined to be damaged and necessitates repair after wiring and power supply faults have been eliminated.
Excessive Zero-Point Drift: The zero-point offset exceeds 0.1mm after 1 hour of cold repose. The internal reference element of the sensor has aged, necessitating repair, as evidenced by the repeated drift that occurs following recalibration.
II. Judgement of Accuracy Anomaly
Excessive Full-Stroke Linearity Error: The sensor output value is more than 0.2mm off from the measured displacement at all three calibration points across the full range. Recalibration is unsuccessful in rectifying this issue, which suggests that the internal measuring elements of the sensor are worn and necessitate repair.
Repeatability Error Exceeding Standard: The sensor's internal moving parts are jammed, necessitating repair, if the output value deviation at the same displacement point exceeds 0.1mm after three consecutive full-stroke forward and reverse movements.
Thermal Drift Exceeding Standard: The sensor's temperature drift characteristic is considered defective and necessitates repair if the measured displacement value deviates from the theoretical thermal expansion value by more than 0.3mm after excluding installation misalignment and the hot runner is heated to operating temperature and held for 1 hour.
III. Evaluation of Functional Anomalies
Alarm Interlock Completely Failed: The sensor output link is considered defective and necessitates repair if the system fails to generate any alarms when the displacement exceeds the limit, after the PLC program and threshold setting issues have been eliminated.
Physical Structural Damage: Immediate repair is required for visible physical damage, such as sensor probe deformation from impact, shell fracture, or internal wire breakage.
Long-Term Performance Deterioration: If the sensor has been in continuous operation for more than two years and its accuracy continues to decrease during periodic recalibration, resulting in a failure to meet the hot runner displacement monitoring and early warning requirements, it necessitates factory recalibration and repair.
The domestically produced low-cost Hall effect displacement sensor you select is fully compatible with this set of judgement criteria. The judgement can be quickly completed on-site by ordinary maintenance engineers, thereby avoiding unnecessary return-to-factory repair costs.
