How to Judge Whether Thermocouple Shielding Layer Fails

For hot runner thermocouples to withstand external electromagnetic interference, the shielding layer is an essential component. Temperature data will appear incorrectly and jump wildly once it fails. Shielding performance can be promptly confirmed by mastering rapid judgment techniques.

First, check the stability of the temperature data in real time. In a normal stable heating state, it is initially determined that the shielding layer fails and is unable to effectively isolate electromagnetic interference if the temperature value suddenly jumps up and down irregularly without changing any parameters and the fluctuation range is large while other electrical equipment in the workshop is operating normally.

Conduct a start-stop comparison test for the equipment. Activate high-power devices close to the hot runner, such as servo motors and frequency converters. The shielding function is invalid if the temperature reading clearly varies in time with the equipment's operation, indicating a substantial invasion of the signal line by external electromagnetic waves.

Third, check how the shielding wires look. Verify if the outside braided shielding mesh is loose in the lap joint position, cracked, peeled off, or locally fractured. The most direct cause of shielding layer failure is external harm.

Fourth, verify the state of grounding. The single-point grounding mode is used by standard insulated wires. Even if the outside construction is intact, shielding failure will result directly if the grounding wire falls off, is in a virtual connection, or is inadvertently connected to multi-point grounding.

Rearrange wiring paths away from high-current heating lines, standardize single-point grounding wiring, replace all high-quality shielded compensation wires promptly after confirming shielding failure, and fully restore the thermocouple signal transmission system's anti-interference capability.333