1. Connection Setup – where and how to connect.
2. Configuration Settings – required communication parameters.
3. Register Sets – available parameters and their mapping.
4. Reading Registers – request and response examples.
5. Units and Conversions – how to interpret values.
6. Error Handling – common issues and resolutions.

 Note: This guide assumes prior knowledge of ModbusRTU/TCPIP. If you are unfamiliar with the protocol, you may struggle to apply the steps described.

Connection Setup

Modbus RTU

Connect to pins 21 (L1/A+) and 22(L2/B-) on the CORE terminal strip.

Modbus TCPIP

Connect the Local LAN port of the Core to your General System.

If your Metacentre Core is connected to your General System with Modbus TCPIP, it is still possible to view the dashboard on your computer.

Wiring Requirements:

Modbus RTU

1. Use 0.34 mm² 2-core twisted pair, earth-screened cable (EU/UK).
2. Use RS485 cable such as Belden 3105A (22 AWG, shielded, stranded) in the USA.
3. Always check polarity.
   

Modbus TCPIP

1. Minimum Cat5e S/UTP or S/FTP (wire braid shielded) Ethernet cable
   
2. Maximum Length: 100 m
   

Configuration Settings

To configure the Modbus settings, you need an Admin level account to access the Modbus Menu.

The configuration settings are editable so you can adjust the settings to the ones your system uses.

The default settings of the Modbus RTU and TCPIP are the following:

Modbus RTU

1. Baud Rate: 9600
2. Data Bits: 8
3. Stop Bits: 1
4. Start Bits: 1
5. Parity: None
   

Modbus TCPIP

1. Port: 50011
   

The default Node address is 85 (Dec), 55 (Hex).

Register Sets

1. Includes all parameters visible on the Metacentre Core.
2. For a full list, see Management System Register Mapping in this article.

1. Provides extended access to parameters of the air compressors installed and connected to the Metacentre Core.
   
2. For a full list, see Air Compressor/Asset Register Mapping in this article.
   

Addressing Notes

1. Entering 0x3406 in software which applies these offsets, may shift the address incorrectly → Illegal Data Address errors.
   

1. Check your software settings for “0-based addressing” or “native addressing.”
2. If only Modicon convention is supported, adjust manually (e.g., add 40001).
3. If possible, confirm using a Modbus analyser.
   

Example Queries

1. Address = 0x55 (Slave address in Hex)
2. Function Code = 0x03 (Read Holding Registers)
3. Register Address = 0x4006 (The address of the register to be read)
4. Number of Registers = 0x0002 (The number of registers expected)
5. CRC = Auto-Generated Check Sum

Register List

1. 0x01 = Running
2. 0x02 = Loaded
3. 0x04 = Error
4. 0x08 = Alarm
5. 0x10 = Available

1. 1 L/s = 0.06 m³/min = 2.11888 CFM
   

1. 1 W/(L/s) = 0.016666 kW/(m³/min) = 0.00047195 kW/CFM
   

1. 1 Wh = 3600 J

1. Unit = mbar = 0.001 bar

1. Unit = m°C = 0.001 °C

1. Unit = %

1. Unit = W
   

1. 0x00 = Off
   
2. 0x01 = On

Error Handling

1. Verify Hardware setup
2. Check wiring, polarity, Modbus Master connection...
   
1. If a valid connection exists, there should always be a response

1. Validate communication with Modbus Master.
2. Confirm baud rate, parity, stop bits, IP settings...
   

1. Check register exists and request is valid.
   
2. Common issues:
   
1. Incorrect data byte size in the request
   
2. Invalid command code
   
3. Attempting to access a non-existent register

1. Contact Metacentre Support.

Important Notes

1. Only troubleshoot if you have ModbusRTU experience.
2. Test first by reading a known register.
3. Metacentre provides registers and examples but does not configure third-party SCADA/BMS software.
4. Integration and correct use of registers is the user’s responsibility.