I. Preparation prior to calibration
Tools: Grade 0 feeler gauge, Grade 0 standard gauge block, digital multimeter, existing industrial control computer in the workshop, and simple host computer software for the sensor.
Prerequisites: The hot runner is cooled to room temperature (25℃), the sensor is mounted and securely fastened, the device is preheated for 15 minutes, and the wiring is verified to be secure. Additionally, the 4~20mA output signal must be normal.
II. Cold zero-point calibration
Return the heated runner plate to its initial zero position. Confirm that the Hall probe is in complete contact with the heated runner plate, with a gap of no more than 0.01mm, using a Grade 0 feeler gauge.
Click the "Zero-point calibration" icon in the host computer software, set the current displacement value to 0mm, and verify that the multimeter output signal is 4mA with a deviation of ≤0.1mA.
III. Calibration at full scale
Select a Grade 0 standard gauge block that is the same thickness as the sensor's preset full-scale displacement value. Position the gauge block between the Hall probe and the heated runner plate, ensuring that it is securely installed.
Click the "Full-Scale Calibration" icon in the host computer software, adjust the current displacement value to the gauge block's standard thickness, and verify that the multimeter output signal is 20mA with a deviation of no more than 0.1mA.
IV. Correction and Verification of Linearity
Insert standard gauge blocks of corresponding thicknesses into each of the three intermediate calibration points, which are evenly spaced between 0 and full scale. Record the difference between the sensor output value and the standard gauge block value.
Fine-tune the linearity correction coefficient in the host computer until the error at all points is ≤0.1mm, achieving full-scale linearity compliance, if the deviation at any point exceeds 0.1mm.
V. Hot Dynamic Calibration
The hot runner system should be initiated to reach the designated operating temperature and maintained at this temperature for a duration of 10 minutes. The measured displacement value of the Hall sensor and the theoretically calculated value of thermal expansion should be recorded simultaneously.
Fine-tune the sensor mounting coaxiality to eliminate systematic errors caused by installation misalignment if the deviation exceeds 0.2mm, until the deviation is controlled within the allowable range.
VI. Archiving and Post-Calibration Verification
Confirm that the hot runner plate is manually pushed to complete three full-stroke forward and reverse movements, with a repeatability error of ≤ 0.05mm and no data skipping.
The entire calibration process is completed by saving all calibration parameters, generating and archiving calibration records.
In hot runner scenarios, this set of operating procedures is entirely compatible with Hall displacement sensors that are domestically produced. The process can be independently completed on-site by ordinary maintenance engineers without the need for specialised calibration personnel or expensive dedicated equipment.
