Based on the background you previously focused on regarding hot runner thermocouple cold junction compensation calibration, the following characteristics can help determine if calibration is needed:
Abnormal Temperature Measurement Deviation: When the actual temperature of the hot runner is stable, if the difference between the thermocouple reading and the standard thermometer reading consistently exceeds ±1℃, and after ruling out issues such as sensor aging and wiring faults, it is highly likely due to cold junction compensation drift.
Changes in Environmental Conditions: New heat sources are added around the cold junction connection area, the ambient temperature fluctuates significantly, or a thermocouple replacement or temperature controller firmware upgrade has recently been completed, causing a change in the cold junction temperature reference.
Expired Periodic Calibration: According to industrial metrology standards, thermocouple cold junction compensation needs to be calibrated every 3-6 months. Calibration must be performed after the expiration date to avoid long-term drift and accumulated errors.
Troubleshooting Indicators: If the thermocouple hot junction is confirmed to be normal and the wiring is not loose, but a systematic fixed temperature drift still occurs, the root cause is generally inaccurate cold junction compensation, requiring immediate calibration.
