Em340 Modbus Register 36: Dev sys L-N

Technical Definition

The register dev sys L-N at address 36 is used to monitor dev sys l-n on the Em340.

• Protocol: Modbus RTU
• Data Type: S DWORD R
• Unit: V
• Access: Read Only

How to Read (Python pymodbus)

Use this code snippet to read this specific value via RS485:

from pymodbus.client.sync import ModbusSerialClient

client = ModbusSerialClient(method='rtu', port='/dev/ttyUSB0', baudrate=9600)
client.connect()

# Read dev sys L-N (Address: 36)
# Note: Check if your device uses 0-based or 1-based addressing
result = client.read_input_registers(address=36, count=2, unit=1)

if not result.isError():
    print(f"Raw Value: {result.registers}")
else:
    print("Error reading register")

client.close()

Integration (Home Assistant)

Paste this into your configuration.yaml:

- platform: modbus_controller
  name: "dev sys L-N"
  address: 36
  value_type: S_DWORD_R
  unit_of_measurement: "V"

Connection Diagram

Here is the standard RS485 wiring for this configuration:

graph TD
    PLC[Host Controller / Home Assistant]
    Device[Em340]

    PLC -- "A+ (D+)" --> Device
    PLC -- "B- (D-)" --> Device
    PLC -- GND --> Device

💡 Engineer's Insight

Analysis: System Line-to-Neutral voltage (Volts). Measures voltage between each phase and neutral.

Troubleshooting: Zero indicates no power at the device, loose neutral connection, or sensor fault.