Default Aio 422 R1 Plc Modbus Register 143: Aio prefix AI4 mV

Technical Definition

The register aio prefix AI4 mV at address 143 is used to monitor aio prefix ai4 mv on the Default Aio 422 R1 Plc.

• Protocol: Modbus RTU
• Data Type: U WORD
• Unit: mV
• 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 aio_prefix AI4 mV (Address: 143)
# Note: Check if your device uses 0-based or 1-based addressing
result = client.read_input_registers(address=143, 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: "aio_prefix AI4 mV"
  address: 143
  value_type: U_WORD
  unit_of_measurement: "mV"

Connection Diagram

Here is the standard RS485 wiring for this configuration:

graph TD
    PLC[Host Controller / Home Assistant]
    Device[Default Aio 422 R1 Plc]

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

💡 Engineer's Insight

Analysis: Analog Input 4 measurement in millivolts (mV). Represents the raw voltage signal from a sensor.

Troubleshooting: Zero value may indicate open sensor, wiring fault, or sensor failure. Check physical connections and sensor diagnostics.