Preparation for Calibration Safety and Conditions: Before the calibration, cool the hot runner system to below 60°C, taking steps to avoid burns from high temperatures.
Prepare a certified Class II standard platinum-rhodium/platinum thermocouple, a low-potential DC potentiometer with a 0.02-degree accuracy, and a dry block furnace. Confirm that all standard equipment is within its calibration validity period and has an accuracy greater than one-third of the allowed error of the thermocouple being calibrated.
Preheat the Husky thermostat and hot runner system for 30 minutes, checking that the thermocouple wire is secure, the temperature field is steady, and there are no basic hardware flaws like loose connections or short circuits.
Thermocouple Temperature Field Comparison Calibration: Bundle the hot junctions of the Husky thermocouple to be calibrated and the standard thermocouple 2-3 times with platinum wire, making sure that their measuring ends are totally in contact and on the same temperature plane.
Calibration for Thermocouple Body Temperature Field Comparison Set up 3-5 calibration points to cover common temperature measurement ranges for hot runners (100℃, 300℃, 500℃, and 800℃ for K-type thermocouples). Increase the temperature gradually from low to high, keeping each value for 15-20 minutes and ensuring a temperature change of ≤0.2℃/min.
Take cyclical readings in the forward and backward order "standard-calibrated-standard," measuring each temperature point at least four times. Record the standard thermocouple's measured thermoelectric potential value as well as the calibrated thermocouple's output value. Calculate the actual temperature using the matching national standard thermoelectric potential-temperature conversion table, then calculate the indicator error for each location.
Full-Link Calibration
Calibrate the compensation lead by connecting both ends to a standard thermocouple and a standard temperature measurement device. Put the heated end in a 100℃ boiling water bath and the cold end in a 0℃ freezing point apparatus. Measure the circuit thermoelectric potential and compare it to the theoretical thermoelectric potential on the standard calibration table to ensure the discrepancy is not more than ±5μV. Verify the polarity at the same time: red is positive and the opposite colour is negative, to avoid reversing the connection, which might double the temperature measurement variance.
To calibrate the cold junction compensator, place it in a constant temperature chamber and set three common room temperature points: 20℃, 25℃, and 30℃. Connect the cold end of the compensator to the freezing point apparatus (0℃) and measure the compensated thermoelectric potential output. Compare this to the theoretical compensated potential to ensure the compensation deviation does not exceed ±0.1℃.
Thermostat Parameter Configuration Calibration: Press and hold the "Set" button on the Husky thermostat panel for 3-5 seconds, then input the device administrator password, navigate to the "Advanced Configuration" menu and select the "Thermocouple Calibration/Temperature Compensation" option.
The ambient temperature at the temperature controller's terminals was measured, and the cold junction compensation temperature parameter on the panel was set to the measured value to eliminate system faults caused by cold junction drift.
The temperature controller's multi-point calibration table was updated progressively with the error correction values for each calibration point. To reduce thermocouple nonlinearity errors, the system created a linear compensation curve throughout the whole temperature range.
The temperature controller's PID self-tuning capability was enabled. The system optimised the P, I, and D values to prevent temperature control overshoot and oscillation.
Closed-loop verification after calibration: Once all settings had been modified, the configuration was saved and the advanced menu was closed. To avoid unintentional modifications to calibration settings, parameter modification permissions were secured using a password.
The temperature was raised to the standard manufacturing temperature and maintained at that level for two hours. Multiple temperature points were randomly chosen from the whole temperature range for comparative testing with normal thermocouples. The full-temperature-range temperature measurement variation was ≤ ±1℃, temperature fluctuation was ≤ ±1℃, with no drift or leap. The calibration operation was then completed.
This rigorous calibration technique fully meets industrial metrology calibration standards, eliminates Husky thermocouple end-to-end system flaws, and ensures long-term accuracy of hot runner temperature measurements.
