Why Is Polarity Important for Hot Runner Thermocouple Installation?

Polarity is a critical but often neglected factor in hot runner thermocouple installation. Reversed polarity causes incorrect temperature readings, system alarms, heater burnout, and severe production risks. Thermocouples generate a millivolt-level signal based on temperature difference, and reversed positive and negative wires completely invert the measurement. K-type and J-type sensors both have strict polarity requirements, usually marked by color-coded cables. Controllers may display abnormally low or fixed temperatures when polarity is wrong. In multi-zone molds, incorrect wiring is a top cause of startup failures. This article explains the dangers of reversed polarity, identification methods, visual inspection tips, and correction steps, helping technicians avoid common wiring mistakes during installation and replacement.