A heat-sealing temperature controller should be selected for the measured thermal zone, not treated as a guarantee of seal quality. The same distinction applies to electronics equipment: a PID controller can regulate a qualified preheat zone, but that does not make it a complete programmable solder-reflow system. Define the process requirement first, then match the sensor, controller and switching hardware.
What does the controlled temperature represent?
In a bag sealer, the displayed process value may come from a sensor embedded in a heater block. That reading is not automatically the temperature of the film interface. The distance from the heater to the material, contact conditions and production speed affect the relationship. Document the sensing point and verify how the indicated value relates to the workpiece under the intended operating conditions.
The WEHO TX4-S controller provides a temperature-control interface with PID and ON/OFF modes described in its manual. Choose the input for the actual thermocouple or RTD, including the correct configured sensor type. A plausible displayed value alone is not proof that the selected input and installed sensor match.
Heat sealing needs a process window, not just an SV
A useful specification records material construction, sealing temperature exposure, dwell time, pressure and the required quality check. The controller set value is only one part of that specification. Do not prescribe a universal temperature for an unspecified laminate or compensate for a mechanical pressure fault by continually raising the setpoint.
| Machine variable | Question to resolve |
|---|---|
| Measured temperature | Where is the sensor, and how does it relate to the sealing surface? |
| Dwell or travel speed | How long does the material receive the intended heat? |
| Pressure and alignment | Is contact uniform across the useful seal width? |
| Finished seal | Which agreed inspection or test confirms acceptance? |
Match the controller output to the power stage
Read the complete order code on the delivered unit. The source-photographed example is TX4-S W1T/R-2. Its markings must not be used to assign every option in the TX4 family to every unit. Confirm the populated control output and its configuration before preparing the machine wiring.
The manual specifies an SSR drive signal of 12 VDC ±2 V, with a maximum output current of 20 mA. This is a control signal for compatible switching equipment, not a supply for the heater itself. The heater branch, switching device, protection and thermal management require their own load-based design. Keep any required independent over-temperature protection separate from ordinary regulation.
Be precise about a reflow application
Solder reflow is defined by a material- and assembly-appropriate time–temperature process. A single measured zone and set value do not establish that profile. The matched TX4 documentation used here does not establish a multi-segment ramp/soak recipe function, so it should not be advertised as a complete reflow-profile programmer on that basis.
A TX4 may be considered for a defined constant-temperature or preheating zone when the overall equipment design supports it. Measure the relevant board or assembly temperature using an appropriate validation method; do not substitute the controller’s heater-sensor reading for the workpiece profile. The system designer must account for timing, transport and any other zones needed by the process.
Fit and commission the real assembly
The TX4-S source manual shows a 48 × 48 mm face with a thin front projection and a through-panel retained body. Keep the housing and terminals behind the panel; it is not a rail-mounted module. Use the matched cutout drawing and required spacing instead of sizing the opening from the face alone.
Before tuning, confirm sensor polarity and type, control action, output compatibility and a stable mechanical process. After commissioning, compare operation under the expected production conditions and retain the resulting settings with the machine record. A stable displayed temperature is useful evidence about the measured zone, but finished seals or assembled boards need their own acceptance evidence.
Frequently asked questions
Does the same SV mean the same seal quality?
No. The indicated set value does not fix the film temperature, dwell time, contact pressure or material properties. Confirm the process window and inspect or test the finished seal against the agreed acceptance criteria.
Can the SSR drive output supply the heater directly?
No. The manual specifies a 12 VDC ±2 V control signal with a maximum current of 20 mA. Use a compatible external switching stage and a separately designed heater-power circuit.
Questions to include in the enquiry
Send the controller order code, sensor type and position, heater supply and load, switching interface, panel arrangement and intended material or thermal process. For sealing, include speed or dwell and quality requirements; for electronics, explain whether the duty is a fixed preheat zone or a complete profiled process. Ask WEHO to confirm the matching controller configuration before finalising the control-panel bill of materials.
