How to Determine if a Sensor Needs Retesting

I. Events That Trigger Retesting Requirements

Heater Leakage Fault: After leakage repair and sensor calibration, a comprehensive retest must be initiated immediately to remove remaining crosstalk effects of the leakage on the signal connection.

Power Grid Surge Impact In case of abnormal events such as voltage spikes or power loss in the workplace, testing must be conducted quickly to analyze sensor sampling reference offset produced by high-voltage surges.

After Sensor Physical Relocation/Reassembly After thermocouple probe relocation, reassembly or replacement with a new sensor, testing must be initiated to ensure temperature measurement accuracy and installation fitment.

Long-Term Hot Runner downtime and Restart: Production restart after more than 72 hours of equipment downtime should prompt a complete retest to check for temperature deviation due to moisture absorption in the sensors or low-temperature deformation.

After Temperature Controller Hardware Replacement/Upgrade: After the temperature controller motherboard or signal acquisition module is replaced, testing should be started immediately to verify that the signal matching between the new hardware and sensor is normal.

 

II. Judgment Criteria Based on Data from Operations Threshold

Temperature deviation threshold: If the sensor temperature deviation exceeds ±2℃ in three consecutive samplings (compared with a conventional high-precision temperature measurement device), a retest is instantly triggered.

Temperature Fluctuation Threshold: When the real-time temperature of the temperature controller swings irregularly more than ±3℃ within 10 minutes, it will start a test to check for any signal crosstalk problems.

Heating Response Threshold: When the hot runner is heated at 50℃/h, and the temperature rise of the sensor is delayed more than 30 seconds after the change of heater current, a test is initiated to investigate the temperature detecting block for poor contact.

PID Adjustment Threshold: If the temperature overshoot is more than 5℃ and does not return to the set point within 3 minutes after starting or stopping the heater, a test will be performed to check the effectiveness of the sensor signal feedback.

 

III. Fixed Trigger Conditions of Periodic Nature

Regular Production Rhythm: The equipment runs stably for 8 hours each day, and a full-item retest is triggered every 3 months, together with heater insulation inspection.

High-load continuous production: equipment is in continuous operation 24 hours a day without interruption, and a fixed test is performed every 1.5 to 2 months to minimize insulation aging and signal drift caused by long-term high temperature operation of the sensors.

Process switchover triggering: A specific test is performed before moving from conventional plastics to high-temperature engineering polymers such as PC and PEEK to verify that the sensor's temperature measurement accuracy satisfies the specifications at temperatures above 350℃.

 

IV. Test passing final judgment criteria: After 4 hours of continuous operation, the temperature measurement error of all channels is stably regulated within ±1℃, without jumps or drifts.

There are no aberrant voltage spikes in the sensor at the point of heater start-up and shutdown, and the temperature measurement data reveals no abrupt jumps.

The trial manufacturing of a small batch of 20 molds of products showed no flaws caused by temperature anomalies, such as flash or insufficient glue. The stability of the process fully met the specifications.

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