Thermocouple drift-the gradual change in measurement accuracy-is a common issue in long-running hot runner systems, caused by several environmental and material factors.
High-temperature oxidation changes the chemical composition of thermocouple alloys, altering their thermoelectric behavior and causing consistent drift.
Thermal cycling fatigue creates microstructural changes in the metal wires, gradually shifting voltage output over millions of cycles.
Contamination from plastic vapors, additives, or mold release agents can penetrate the sensor sheath and affect the junction, causing unstable drift.
Diffusion of elements between the thermocouple wire and sheath material at high temperatures changes electrical behavior and reduces accuracy.
Mechanical stress and vibration add physical deformation that contributes to long-term signal shift.
While drift cannot be fully eliminated, high-quality alloys, proper sheath materials, and regular calibration minimize its effect. Understanding drift helps operators schedule maintenance and maintain stable production quality.
