Modbus Sensors

Here is list of tested sensors by HARDWARIO with basic configuration to use:

Name	Type	Notes
Carlo Gavazzi EM1XX Series	Electrometer	Integrated into CHESTER Energy
Carlo Gavazzi EM5XX Series	3-Phase Electrometer	Integrated into CHESTER Energy
ORNO OR-WE-516	3-Phase Electrometer	Integrated into CHESTER Energy
Schneider Electric iEM3000 series	3-Phase Eletrometer	Integrated into CHESTER Energy
LAMBRECHT meteo sensors		Integrated into CHESTER Meteo

Modbus Communication Overview

Figure: Typical Modbus network topology using Modbus RTU and Modbus TCP.

What is Modbus?

Modbus is a widely adopted serial communication protocol originally developed by Modicon (now Schneider Electric) in 1979. It is designed for connecting industrial electronic devices and is commonly used for communication between a supervisory computer and remote terminal units (RTUs) in SCADA systems.

Modbus enables devices to communicate over serial lines (Modbus RTU/ASCII) or over Ethernet (Modbus TCP/IP). It is open, simple, and robust, making it one of the most popular protocols in industrial automation.

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Modbus Variants

Modbus RTU (Remote Terminal Unit)

• Uses RS-485 or RS-232 physical layer
• Binary format (compact, efficient)
• Master-slave architecture

Modbus ASCII

• Similar to RTU but uses ASCII encoding
• Easier to debug manually but slower and less efficient

Modbus TCP

• Runs over Ethernet (TCP/IP stack)
• Client-server model
• No need for device addressing (uses IP instead)

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Hardware Requirements

Modbus RTU

• Master Device (e.g., PLC, gateway, HMI)
• Slave Devices (e.g., sensors, actuators, meters)
• RS-485 Bus (2-wire differential signal, supports up to 32 devices without repeaters)
• Termination Resistors and biasing recommended for signal integrity

Modbus TCP

• Ethernet-enabled master and slave devices
• Network switch/router (optional depending on topology)

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Data Model

Modbus defines data using register-based addressing. The master polls the slave using function codes to read or write data.

Address Types

• Coils: 1-bit (read/write)
• Discrete Inputs: 1-bit (read-only)
• Input Registers: 16-bit (read-only)
• Holding Registers: 16-bit (read/write)

Common Function Codes

• 01 Read Coils
• 02 Read Discrete Inputs
• 03 Read Holding Registers
• 04 Read Input Registers
• 05 Write Single Coil
• 06 Write Single Register
• 16 Write Multiple Registers

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Example Output (Parsed JSON)

{
  "device_id": "MODBUS-001",
  "timestamp": "2025-04-29T08:30:00Z",
  "holding_registers": {
    "40001": 1234,
    "40002": 5678
  },
  "input_registers": {
    "30001": 55.2
  },
  "coils": {
    "00001": true,
    "00002": false
  }
}

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Applications

• Industrial automation
• Building management systems (BMS)
• SCADA systems
• Motor controllers, inverters, and PLCs
• Environmental and energy monitoring systems

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Advantages of Modbus

• Open and widely supported
• Simple and easy to implement
• Versatile with both serial and Ethernet support
• Works over long distances with RS-485

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Limitations

• No native security or encryption
• Master-slave model (RTU) limits concurrency
• Limited data size per transaction (typically 256 bytes)
• Requires proper configuration of bus termination and addressing