Based on your previous focus on the wear and corrosion of temperature sensors in hot runner scenarios, repair calibration, and the prohibition of production with faulty sensors, common reasons for calibration failure are as follows:
Defects in Thermal Conductivity: Oxidation and scale buildup on the sensing surface, uneven application of thermal grease, or gaps in the liner after repair obstruct heat conduction, leading to temperature measurement lag and excessive deviation.
Aging of the Sensing Element: Long-term high-temperature corrosion can cause the resistance of the thermocouple/platinum resistance thermometer to drift beyond tolerance, resulting in loose internal wiring and an inability to output accurate temperature signals.
Installation and Fit Misalignment: Improper installation of the temperature sensor, leaving gaps between it and the outer wall of the hot runner channel, interrupts the heat conduction path, causing the measured temperature value to deviate significantly from the true temperature.
Reference Source Error: The standard temperature source used for calibration is inaccurate, and failure to perform prior traceability verification leads to a misjudgment of the temperature sensor calibration as unqualified.
