How to Calibrate Zero Drift of Hot Runner Sensors

Zero drift may be calibrated in just four stages using common equipment. The process is straightforward and precise:

1. Pre-treatment for Thermal Stabilization: To enable the sensor to reach complete thermal stability, first heat the hot runner to the standard operating temperature for daily production and hold it there for 30 minutes. This is essential for precise calibration and prevents further variations brought on by temperature changes.

2. Complete Depressurization and Settling: Make sure the real pressure inside the runner is zero by completely depressurizing the injection molding machine to release the melt pressure. After that, let it stand for ten minutes so the sensor output can stabilize completely. After depressurization, avoid calibrating right away as this could lead to residual pressure mistakes.

3. Modifying Zero Point Parameters: The type of sensor determines how this works.

In the injection molding machine control system or sensor amplifier interface, directly set the current zero-pressure output to the standard zero point (4mA by default for current-type sensors) for models with built-in amplifiers (such as the Kistler 6125A). Then, save the values.

External Amplifier/Passive Model: Recalibrate the zero-point reference and clear the present zero-pressure output offset to zero in the injection molding machine signal acquisition system.

4. Verify Calibration Results: Check the zero-pressure output once again after repeating the "depressurize → let stand" process. The calibration is deemed successful if the variance is less than 0.02 mA.

It is advised to retest every two weeks following calibration if the recurring drift is due to age in order to monitor deviation changes and prevent severe drift from impacting production.