Default Aio 422 R1 Plc Modbus Register 140: Aio prefix AI1 mV

Technical Definition

The register aio prefix AI1 mV at address 140 is used to monitor aio prefix ai1 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 AI1 mV (Address: 140)
# Note: Check if your device uses 0-based or 1-based addressing
result = client.read_input_registers(address=140, 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 AI1 mV"
  address: 140
  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 voltage from AI1. Units: Millivolts (mV).

Troubleshooting: Sensor fault, wiring issue, incorrect sensor type selected, or PLC input configuration error.