Digital Temperature Controller with Modbus RS485
Monitor temperature locally and access controller settings remotely
with the Digital Temperature Controller with Modbus RS485.
The controller combines seven-segment temperature and setpoint
displays, four-button operation and two relay outputs with
Modbus RTU communication.
Key Features
- Seven-segment displays:
View measured temperature and the selected setpoint. - Four-button operation:
Adjust settings using SET, UP, DOWN and ENTER. - Two relay outputs:
Operate connected equipment according to the controller’s
automatic sequence, using one shared temperature setpoint. - Modbus RTU over RS485:
Connect to a compatible PLC, HMI or computer for remote access. - Remote monitoring:
Read temperature, setpoint, relay difference, calibration,
relay status and slave ID. - Remote setting changes:
Write individual settings or multiple consecutive registers. - Adjustable calibration:
Change calibration through the front panel or Modbus. - Saved settings:
Retain the setpoint, relay difference, calibration and slave
ID after power is switched off. - Relay operation tests:
Test either relay with a one-second ON command through Modbus. - Startup identification:
Display the slave ID for approximately one second at power-on.
Technical Specifications
| Product Name | Digital Temperature Controller with Modbus RS485 |
|---|---|
| Display | Seven-segment temperature and setpoint displays |
| Control Buttons | SET, UP, DOWN and ENTER |
| Relay Outputs | Two outputs with one shared temperature setpoint |
| Setpoint Adjustment | 1–700 °C software setting range |
| Relay Difference | Adjustable from 2–255 °C |
| Calibration | Adjustable through the front panel or Modbus |
| Communication | Modbus RTU over RS485 |
| Baud Rate | 9600 baud |
| Serial Format | 8 data bits, no parity, 1 stop bit — 8N1 |
| Slave ID | 001–247; default 001; adjustable through Modbus |
| Modbus Read Function | 03 — Read Holding Registers |
| Modbus Write Functions | 06 — Write Single Register 16 (0x10) — Write Multiple Registers |
| Settings Storage | Nonvolatile memory |
Specification note:
The software setpoint range is not a measurement accuracy or
sensor-range specification. Confirm the sensor type, supply
voltage, relay contact ratings, dimensions and operating limits
for the supplied model before installation.
Modbus Register Map
To read all seven registers, use function
03, starting address 0
and quantity 7.
Some master software labels the first register as 40001.
| Protocol Address | Register Label | Parameter | Access |
|---|---|---|---|
| 0 | 40001 | Measured Temperature | Read only; signed whole °C |
| 1 | 40002 | Temperature Setpoint | Read and write |
| 2 | 40003 | Relay Difference | Read and write |
| 3 | 40004 | Calibration Value | Read and write; raw value 30 is neutral in normal operation |
| 4 | 40005 | Relay A | Read status; write 1 for a one-second ON test |
| 5 | 40006 | Relay B | Read status; write 1 for a one-second ON test |
| 6 | 40007 | Slave ID | Read and write; valid values 1–247 |
Relay status indicates the commanded output, not physical
contact feedback. A multiple-register write that includes
either relay-test register requires value 1 there and
triggers its test.
How to Use the Controller
- Switch on the controller. The slave ID appears for
approximately one second. - Read the measured temperature and saved setpoint.
- Press SET, then use UP or DOWN to adjust the setpoint.
- Press ENTER and release all buttons to save and resume
normal operation. - For remote access, configure the Modbus master with the
correct slave ID and 9600 baud, 8N1.
Leave power on for at least one second after saving settings.
Automatic temperature updates pause while a setting menu
is open. Exit the menu to resume normal operation.
Related Products and Support
Explore our
product range
to find equipment for your temperature monitoring and
control requirements.
For product specifications, availability and assistance,
contact us about the Digital Temperature Controller with Modbus RS485
.
Learn More About Modbus Communication
For technical information about Modbus messages and function codes,
read the
official Modbus Application Protocol Specification
published by the Modbus Organization.
Frequently Asked Questions
What is Modbus RS485 communication?
RS485 provides the communication interface, while Modbus RTU
defines the messages exchanged between the controller and
a compatible master. The master can request temperature
readings and access supported settings.
Can this controller connect to a PLC or HMI?
Yes. Use a PLC or HMI that supports Modbus RTU master
communication over RS485. Set the correct slave ID and
configure 9600 baud, 8 data bits, no parity and 1 stop bit.
Can I change the setpoint remotely?
Yes. Write the required setpoint to protocol address 1,
also labelled register 40002. The permitted software
setpoint range is 1–700 °C.
Can multiple settings be changed in one request?
Yes. Function 16 (0x10) writes multiple consecutive registers.
For example, starting address 1 with quantity 3 updates
the setpoint, relay difference and calibration.
Are the two relays separate temperature channels?
No. Both relays belong to one temperature controller and
use a shared setpoint. Refer to the user manual for each
relay’s automatic switching sequence.
How do I test a relay through Modbus?
Write 1 to address 4 for Relay A or address 5 for Relay B.
The selected relay is commanded ON for approximately one
second before returning to automatic control. Confirm
that briefly energizing the connected load is appropriate
before testing.
Why might a relay remain ON after its test?
The relay returns to its current automatic command when
the test ends. If automatic control requires ON, the relay
remains ON. The test does not force an OFF state afterwards.
Can I change the Modbus slave ID?
Yes. Write a value from 1 to 247 to protocol address 6,
also labelled register 40007. The reply uses the old ID;
use the new ID for subsequent requests.
Can I assign slave ID 000?
No. Address 000 is reserved for broadcast messages.
Individual controllers must use IDs from 001 to 247.
Are settings saved after power is switched off?
Yes. The setpoint, relay difference, calibration and slave
ID are stored in nonvolatile memory. Allow at least one
second after saving before switching off power.
Why does reading ten registers return an error?
The controller provides seven holding registers. Read the
complete map using function 03, starting address 0 and
quantity 7.
Does the controller send temperature data continuously?
No. It responds when the Modbus master sends a valid request.
Configure periodic polling on the PLC, HMI or computer
to receive updated readings.
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