What is the interchangeability error of sensors in hot runner systems?

The fixed deviation in temperature measurement results following the interchangeable installation of hot runner sensors of the same model and specification is known as the interchangeability error of hot runner sensors. With a usual deviation range of ±1~3°C, this is a common source of error in hot runner temperature measurements. The quality of the product is directly impacted by excessive mistake. The following are specific explanations:

1. Fundamental Reasons for Errors

Sensor Manufacturing Tolerances: PT100 resistance and thermocouple thermoelectric potential have intrinsic manufacturing tolerances. Different sensors will have output variances even if they have the same index number.

Preload/Contact Force Deviation: The length and machining specifications of various sensor probes vary slightly. Following exchange, there is a further variation of 0.5–2°C due to changes in the contact force and preload at the bottom of the hole.

Mounting Hole Machining Tolerances: Variations in the diameter and depth of mold mounting holes will also increase the mistake by amplifying the contact deviation following interchange.

2. The Effect of Mistakes

Conventional Injection Molding: Product quality is typically unaffected by interchangeability errors of ≤±2℃.

Precision Injection Molding (Tolerance ≤0.01mm)/High-Temperature Injection Molding: Defects including color differences, dimensional fluctuations, and inadequate adhesive can result from even a deviation of ±1°C.

Batch quality problems are directly caused by excessive errors (over ±3°C) in temperature control circuitry.

3. How to Cut Down on Interchangeability Mistakes

Choose Higher Accuracy Sensors: Because Class A thermocouples and AA-grade PT100 have smaller manufacturing tolerances, interchangeability deviations can be controlled within ±1°C.

Re-verify Preload/Contact Force After Interchange: To make sure the contact force satisfies specifications and removes any further installation-related variations, remeasure and set the preload to the standard range after replacing the sensor.

Recalibrate Temperature After Interchange: To counteract interchangeability errors, calibrate the temperature measurement deviation using a standard thermocouple and adjust the temperature controller's correction coefficient.

To reduce manufacturing variations in the sensors themselves, use sensors from the same batch and manufacturer for the same hot runner system.