How Thermocouple Polarity Reversal Causes Hot Runner Temperature Disorder

Thermocouple positive and negative polarity reversal is typically due to reckless operation on site wiring. The appearance is fitted regularly, however the internal thermoelectric signal transmission is fully inverted, resulting in major temperature display distortion and heating logic disorder. Many maintenance professionals cannot identify the polarity reversal problem quickly, resulting in recurrent debugging and broad area defective items, impeding normal production.

The thermoelectric potential signal is sent reversely after the thermocouple polarity reversal. The display temperature will go down when the actual runner temperature goes up and go up when the actual temperature goes down abnormally. The temperature controller totally loses the right judgement and the logic of increasing or decreasing the heating power is inverted. The higher the setting temperature, the lower the real heating, a dangerous dead cycle of temperature control disturbance is made.

In the mild situation, the temperature cannot be continuously raised to the set value, the heating is constantly insufficient, the melt fluidity is poor and there are persistent short shots and weld line faults. In the serious instance, the controller overestimates the overheating, long-time halt heating, and makes the hot runner in the low-temperature abnormal state all the time, and can't manufacture the qualifying items at all. Polarity reversal creates frequent false over temperature and under temperature alerts, which affects the normal production judgement.

Polarity reversal can be judged simply by raising the set temperature a little, if the actual heating does not go up, but the displayed temperature reduces, it can be confirmed as reverse wiring. Just reverse the positive and negative terminals and you are back to regular temperature control. Strictly separate the positive and negative colour codes of the thermocouple throughout the daily installation and replacement, indicate the terminal position, and prevent human wiring errors. polarity detection and wiring operation standardisation can totally prevent temperature disorder faults, caused by polarity reversal