Setting up the DCL 531 RS485 Modbus level transmitter

---

Steps to Update Settings on the DCL 531 RS485 Modbus Level Transmitter #

1. Understand the Modbus Communication Parameters #

• The device communicates using the Modbus RTU protocol over RS485.
• Key configurable parameters include:
  • Device Address: Can be set between 1 and 247.
  • Baud Rate: Options include 4800, 9600, 19200, and 38400.
  • Parity: Options are None, Odd, or Even.

These parameters are stored in the Holding Registers and can be read or written using Modbus function codes:

• Function Code #3: Read Holding Registers.
• Function Code #6: Write Single Register.

2. Identify the Relevant Registers #

The following registers are used for configuration:

• Device Address: Register 0x0002 (Uint16).
• Baud Rate: Register 0x0003 (Uint16).
  • 0 = 4800
  • 1 = 9600
  • 2 = 19200
  • 3 = 38400
• Parity: Register 0x0004 (Uint16).
  • 0 = None
  • 1 = Odd
  • 2 = Even

3. Connect to the Device #

• Ensure the device is powered with a 9–32 VDC supply voltage.
• Connect the RS485 communication lines:
  • A+ (Green wire) to the RS485 A+ terminal.
  • B- (Yellow wire) to the RS485 B- terminal.
• Use a Modbus-compatible software or hardware interface (e.g., a USB-to-RS485 converter and Modbus software like ModScan or QModMaster).

4. Read Current Settings #

• Use Function Code #3 to read the current values of the relevant registers:
  • Read 0x0002 for the current device address.
  • Read 0x0003 for the current baud rate.
  • Read 0x0004 for the current parity setting.

5. Update Settings #

• Use Function Code #6 to write new values to the registers:
  • Write to 0x0002 to change the device address.
  • Write to 0x0003 to change the baud rate.
  • Write to 0x0004 to change the parity.

Example:

• To set the device address to 5, send a Modbus request to write 5 to register 0x0002.
• To set the baud rate to 19200, write 2 to register 0x0003.
• To set parity to None, write 0 to register 0x0004.

6. Reset the Device (if needed) #

• If you need to reset the device to factory settings, follow the instructions in Section 6.3:
  • Connect the Reset input (Pink wire) to 24 VDC at the same time as the positive supply voltage.
  • Disconnect the Reset input after the reset is complete.

7. Verify the Changes #

• After updating the settings, read back the registers using Function Code #3 to confirm the changes.
• Test communication with the updated parameters to ensure the device is functioning correctly.

---

Notes and Precautions #

• Always ensure the device is powered off before making electrical connections.
• Use shielded and twisted cables for RS485 communication to minimize interference.
• If you encounter issues, refer to the troubleshooting section in the manual or contact us for further support.