What Is a Modular Temperature Controller? Types and Selection Criteria
A modular temperature controller is mounted inside the panel, controls temperature with PID and connects to a PLC or operator panel over RS485 Modbus.
A modular temperature controller is a temperature controller mounted inside the panel rather than on the panel door, which holds the temperature read from the sensor at the setpoint with a PID algorithm and connects to a PLC, operator panel or SCADA over RS485 Modbus. The setpoint and the measured temperature are read and written over the communication line. In multi-zone systems such as plastic injection, extrusion, packaging and oven lines, it is used to place a separate controller for each zone and manage them all from one panel.
Models in the catalog
| Model | Supply | Sensor input (product data) | Communication | Size |
|---|---|---|---|---|
| Enda ET1124A | 24 V DC | Thermocouple J, K, L, T, S, R | RS485 Modbus | 29 x 90 x 64 mm |
| Enda ET1124A-RT | 24 V DC | PT100 and thermocouple J, K, L, T, S, R | RS485 Modbus | 29 x 90 x 64 mm |
| GEMO MDTA1TP | 18–32 V DC | Thermocouple J, K, T, S, R and Pt100 | RS485 Modbus RTU | 35 x 102 x 117 mm |
The GEMO MDTA1TP is a single-channel PID controller. Check the output type and mounting method for each model in the datasheet.
Selection criteria
- Sensor input: The controller's input must match the sensor type. If the thermocouple type (J, K, T…) is not set correctly on the device, the reading is wrong. A PT100 sensor needs the ET1124A-RT or the MDTA1TP.
- Supply: The models in the catalog run on 24 V DC (GEMO 18–32 V DC); a DC power supply is needed in the panel.
- Output: The heater is driven through a contactor or SSR from the controller's output. Choose between relay, SSR drive or analog output by how often the heater switches; for frequently switched heaters an SSR is preferred.
- Communication: On an RS485 Modbus line each controller gets its own address; terminating resistors are fitted at the line ends and the baud rate is set the same on all devices.
- Number of zones and space: Each zone needs one controller. The width of the modules (ET1124A 29 mm) determines how many zones fit in the panel.
Common mistakes
- Setting the wrong thermocouple type on the device: The displayed temperature deviates from the real value.
- Extending a thermocouple with copper cable: The cold junction moves to the joint and an error equal to the temperature difference between the joint and the terminal appears; use thermocouple extension cable.
- Wiring the Modbus line as a star: The line must run as a chain from one end to the other and be terminated at the ends.
Modular temperature controllers at Welibaba
The Modular Temperature Controllers category has 3 active products: the GEMO MDTA1TP is listed with a price, and the Enda ET1124A and ET1124A-RT are sold on quotation. Panel-door models with a display are in the PID Thermostats category and explained in the digital temperature controller guide.
Frequently asked questions
What is the difference between a modular temperature controller and a panel thermostat?
A panel thermostat is fitted in the panel door and set with the keys on its front. A modular device sits inside the panel, and setting and monitoring are mostly done over the communication line from a PLC or operator panel.
How many controllers can be connected to one Modbus line?
It depends on the line and device limits; each device gets its own address. Check the number and line length limits in the datasheet and the master device's documentation.
PT100 or thermocouple?
At moderate temperatures a PT100 is more precise and stable; at very high temperatures and where fast response is needed, a thermocouple is used. Check the measuring range in the sensor datasheet. Choose the controller input to suit the sensor.