Switching between J-type and K-type thermocouples in a hot runner temperature control box involves modifying the internal parameter settings of the control box to match the sensor signal. Some older or simpler models may require replacing the hardware temperature control card.
Most modern microprocessor-controlled temperature control boxes (such as HST brands) support direct switching via software menus without hardware replacement. You need to access the temperature control box's parameter settings interface, find the thermocouple type (Sensor Type) option, and change the current "J" to "K" or vice versa. After switching, the temperature control box will automatically adjust its internal non-linear processing and cold junction compensation algorithm to ensure accurate temperature readings. If the equipment is older or does not support software switching, you must power off and remove the current J-type temperature control card, replacing it with a K-type temperature control card, because the internal chips of different temperature control card models are designed for fixed signal curves.
Software Parameter Switching Steps (Applicable to Temperature Control Boxes Supporting Dual-Type Switching)
For modern temperature control boxes equipped with Fuzzy+PID control algorithms and dual-line LED displays, the operation is typically as follows:
Entering Setting Mode: On the temperature control box panel, press and hold the "Set" button (or a specific key combination, such as "Set + Shift") for approximately 3-5 seconds until the display enters the parameter menu interface.
Locating Thermocouple Type Parameter: Use the up and down keys to navigate the menu and find the parameter code representing the sensor type (common codes are Sn, InP, or Sensor).
Modifying the Value: Modify the parameter value to the corresponding type code. Typically, J-type corresponds to code J or a specific number (such as 01), and K-type corresponds to code K or a specific number (such as 02). Refer to the brand's instruction manual for details.
For example, in some instruments, you need to change the window parameter from its default value to a specific value (such as changing 00 to 20) to activate type selection, and then switch between K/J using the up and down keys.
Save and Exit: After making changes, press and hold the "Settings" button or wait for automatic exit without operation. The instrument will reinitialize and display the new thermocouple type identifier.
Hardware Replacement Steps (Applicable to models that do not support software switching)
If your temperature control box only supports a single type of temperature control card per card, a physical replacement is required:
Complete Power Off: Turn off the main power switch of the temperature control box and unplug the input power cord, ensuring safe operation.
Remove the Old Card: Open the temperature control box panel and locate the corresponding number of temperature control cards. Loosen the fixing screws or clips and carefully remove the current J-type (or K-type) temperature control card. Be careful not to use excessive force and damage the socket.
Install the New Card: Align the spare K-type (or J-type) temperature control card with the slot, ensuring good pin contact, and tighten the screws.
Check Wiring: Although the temperature control card has been replaced, confirm that the externally connected thermocouple wire is indeed the type you need (replace J-type wire with K-type wire), and that the positive and negative terminals are correctly connected.
Power-on Test: Restore power and observe whether the display shows the temperature normally and without errors (such as thermocouple disconnection alarm).
Key Precautions
Sensor Consistency: Before switching the temperature control box type, it is essential to confirm that the physical type of the thermocouple installed on the mold is consistent with the temperature control box setting. If the temperature control box is set to type K but a type J thermocouple is actually connected, it will cause a serious deviation in temperature readings, potentially burning out the heating coil or rendering the product unusable.
Compensation Wire Matching: If the thermocouple extension wire (compensation wire) is also involved in the connection, ensure that the extension wire material also matches the new thermocouple type (J or K), otherwise new errors will occur at the junction box.
Retuning: After the type switch is completed, it is recommended to perform a one-time PID auto-tuning of the temperature control system to adapt to the response characteristics of the new sensor and achieve optimal temperature control accuracy (up to 0.5℃).
Prohibited Operation While Powered On: It is strictly forbidden to insert or remove the temperature control card while the power is on, as this can easily cause the circuit board to burn out.
