AMT Dewpoint Transmitter Modbus Setup Guide Issue 1

1 Introduction Modbus 1.1 What is Modbus Modbus is a digital communication protocol used in industrial automation to enable data exchange between multiple electronic devices and a central controller, such as a programmable logic controller (PLC). It supports the transfer of process values, status signals and control commands between field instrumentation and higher level controllers or data acquisition systems, with communication flowing in both directions. Within the Modbus protocol, the device that initiates data requests is called the Modbus **client**, and the devices that respond and supply...

2 Getting Started Before starting please check you have all the necessary components. If you do not have access to Modbus test software, please install it. The software is free and this guide will explain how to access it. 3 Equipment Required Please ensure you have the following components to set up your AcuDew Modbus RTU dewpoint transmitter. TRANSMITTER CABLE USB CONVERTER POWER SUPPLY 4 Downloading and Installing Modbus Test Software Access to Modbus software is necessary for testing the equipment; however, you do not require a specific version to do this. For this tutorial we will use GModbus,...

4.3 To download the Gmodbus zip file, select the option Modbus RTU/TCP tester (free) (Fig. 2). Download the Modbus file. 4.4 Right click and select Extract All (Fig. 3). 4.5 Open the folder titled GModbus and select the Application file (Fig. 4). The Modbus tester GModbus dialogue box will open (Fig. 5). You have now successfully installed your software. 5 Connecting the Transmitter5.1 Equipment Set Up 5.1.1 Loosen the screw terminals in your converter, do not remove fully (Fig. 6). 5.1.2 Connect the wires to the screw terminals (Fig. 7 and 8). NOTE: If your USB to RS485 converter is different...

5.1.3 Connect the M12 screw collar to the transmitter (Fig. 9). 5.1.4 Connect the USB converter to the USB cable. 5.2.1 Open Device Manager on your PC. 5.2.2 Connect the USB cable to your PC and switch on the power supply. 5.2.3 Ports (COM & LPT) appear in the list. Click on Ports (COM & LPT) to find the COM number for USB-SERIAL CH340 (Fig. 10). 5.2.4 Return to the GModbus software. The screen Modbus tester GModbus will open. Enter the COM number and use the information in the table titled Communication Parameters (Fig. 11) complete the settings highlighted in the Modbus tester GModbus screen...

5.2.5 Click Connect to port. Click Read registers (Fig. 13). Once the correct port is selected, the following data will appear on the right hand side of the screen (Fig. 14). This confirms the connections are correct and the transmitter is functional. To measure dewpoint in degrees Celsius change the read Modbus address from 3009 to 3001 and click ‘Read registers' again. The ‘32bit value' column will display the dewpoint, measured by the transmitter, in degrees Celsius (Fig. 15). You can now integrate the transmitter into your system. 6 Troubleshooting Error Message If you require any support...

Alpha Moisture Systems Ltd. Network House 5 Lister Hill Leeds LS18 5AZ England Telephone: +44 (0) 1274 733100 Email: [email protected] www.dew-point.com AMT Modbus RTU Setup Guide Issue1 © ALPHA MOISTURE SYSTEMS LTD 2026