What Are The Differences Between Grounded And Ungrounded Hot Runner Thermocouples

The two fundamental structural categories of hot runner thermocouples are grounded and ungrounded junction types, which differ in terms of internal construction, temperature response speed, anti-corrosion performance, and suitable operating conditions. Many users find it difficult to discern between the two types, which leads to incorrect matching selection, slow temperature response, easy signal interference, and a shorter service life.

The hot end alloy connection of grounded thermocouples is directly welded to the metal sheath. Because of the short heat conduction channel and incredibly quick temperature sensing response speed, the hot runner's immediate temperature change may be swiftly recorded. They are appropriate for sequential valve gate systems that need sensitive temperature feedback, high-cycle, high-speed moulding moulds, and nozzle gate temperature monitoring. However, the signal stability is somewhat poor in complex electromagnetic environments because of the direct conduction of the metal sheath and alloy junction, which makes it susceptible to external electromagnetic interference and generates stray current.

Ungrounded thermocouples have an isolated structure, with a high-purity insulation filler entirely sealing and separating the alloy hot end from the outer metal sheath. It can successfully isolate electromagnetic noise and stray current, has strong anti-interference capabilities and high insulation performance, and transmits temperature signals steadily and without bouncing. It is ideal for medical high-precision moulds that need incredibly steady temperature data, intelligent workshops with severe interference, and multi-cavity dense layout moulds. Its drawbacks include a somewhat longer heat conduction path and a slower temperature response time than the grounded type.

In terms of corrosion resistance and service life, an ungrounded fully insulated sealed structure has a longer service life, is more difficult to cause internal oxidation and short circuit failure, and can better separate the erosion of corrosive volatile gas and damp oil mist. The grounded type is better suited for standard operating situations with straightforward surroundings and demanding response times. Accurate selection and full utilisation of the hot runner system's temperature control capability can be achieved by correctly differentiating the structural differences and application circumstances of grounded and ungrounded thermocouples.333