Influencing Factors of Ambient Temperature on Thermocouple Temperature Measurement Accuracy

The majority of technicians in actual injection molding production solely focus on the working temperature inside hot runners, ignoring the impact of the ambient temperature outside the workshop on the thermocouple detection effect. The cold junction reference value of thermocouples will be directly impacted by changes in ambient temperature, leading to a systematic temperature measurement variation that causes hidden issues with precise temperature management.

The thermocouple's cold junction, which is linked to the temperature controller, is in a low-temperature condition for an extended period of time when the workshop's ambient temperature is too low. Insufficient compensation impact results from the system's initial cold junction temperature compensation value not matching the real low-temperature environment. The thermocouple's feedback temperature is currently lower than the hot runner's actual operating temperature. In order to boost the temperature, the temperature control equipment will constantly increase the heating power. This can easily result in imperceptible overheating of the melt inside the flow channel, which can cause issues with carbon deposition, product yellowing, and material breakdown. Such temperature difference is more noticeable, particularly in winter low-temperature production workshops.

Conversely, the cold junction temperature will rise fast and above the typical adjustment range if the ambient temperature is excessively high in the summer or close to high-temperature baking equipment. The thermocouple's temperature signal output will be higher than the actual temperature of the hot runner if the cold junction temperature is too high. Inadequate real melt temperature, poor fluidity, and the potential for molding flaws including weld lines, sink marks, and inadequate product filling are all consequences of the controller cutting off the heating output too soon.

Additionally, the cold junction reference benchmark of thermocouples will continuously fluctuate due to unpredictable ambient temperatures. The temperature control system is unable to provide a steady, continuous temperature adjustment logic because the temperature feedback data is constantly fluctuating. Because each hot runner temperature zone is unable to maintain a balanced heating condition, injection molding operations have challenging parameter solidification and uneven product quality over time.

Furthermore, the effectiveness of thermocouple compensation wires will be impacted by extremely high or low ambient temperatures. Too low of a temperature will make the wire body hard and brittle, increasing the chance of internal wire core fracture, while too high of a temperature would hasten the aging and insulation deterioration of the wire skin. In order to effectively eliminate such interference, businesses should maintain a relatively stable workshop temperature, prevent direct cold and hot winds from blowing at the temperature control box and wiring terminals, appropriately adjust the controller's cold junction compensation parameters in accordance with seasonal temperature changes, and increase the frequency of temperature comparison and calibration in extreme temperature environments. This will eliminate ambient temperature deviation and guaranty that thermocouple detection data is accurate and true.333