Published: 2025-11-11 Article source:
Hello everyone, welcome to General Measure's channel.
In this session, we will demonstrate how to communicate between the GMT-X4 and the Modbus Poll tool via the RS485 serial port.
Communication Methods of GMT-X4
GMT-X4 supports multiple communication interfaces:
Serial Communication (RS232/RS485)
CAN Communication
Ethernet Communication (Modbus TCP/IP)
Field-bus Communication (including PROFINET, EtherCAT, Ethernet/IP, and CC-Link IE)
In this tutorial, we will take RS485 connection as an example.
The procedure for RS232 is similar.
Hardware Connection
First, connect the GMT-X4 instrument to the host computer using the RS485 data transmission interface.
Communication Settings (COM-1)
On the GMT-X4 main interface, press Enter to Calibration Menu, then press the Right Key to enter the Communication Parameter Menu.
1.1 [Slave ID]
Select COM1 and press Enter, then choose 1.1 [Slave ID].
Use the Up/Down Keys to set the value.
Press Enter to confirm.
(Tip: The default value is 01, and the range is 01–99. Ensure the Slave ID of the instrument matches that of the host computer.)
1.2 Baud Rate
Press the Down Key to select 1.2 [Baud Rate].
Use the Up/Down Keys to choose the baud rate.
Press Enter to confirm.
(Tip: The default value is 38400. Make sure the baud rate of both the instrument and the host computer are the same.)
1.3 Communication Protocol
Press the Down Key to select 1.3 [Communication Protocol].
Select Modbus RTU.
Press Enter to confirm.
(Tip: In the demonstration, Modbus Poll software uses the Modbus RTU protocol, please select Modbus RTU here. You may choose other protocols according to your actual needs.)
1.4 Data Format
Press the Down Key to select 1.4 [Data Format].
Choose the default value 8-E-1, then press Enter.
(Tip: Ensure the data format settings match between the instrument and the host computer.)
1.5 Double Word Mode
Press the Down Key to select 1.5 [Double Word Mode].
Choose the default value AB-CD, then press Enter to confirm.
1.6 Continuous Transmission Interval
Since this demonstration uses the Modbus RTU protocol, which is not a continuous transmission protocol, this parameter does not need to be set.
(Tip: The continuous transmission interval is used to prevent data confusion caused by excessive transmission speed. If needed, set this parameter according to actual requirements.)
PC Software Settings
After completing the instrument settings, open your computer and configure the Modbus Poll software as follows:
Check the Serial Port
Open Device Manager, locate Ports (COM & LPT), and find the current RS485 port name.
In Modbus Poll, click Read/Write Definition, and in the Slave ID field, input the Slave ID you set in the instrument.
Establish the Connection
Click Connection → Connect.
In the connection setup:
Select the same data format as you set on the GMT-X4.
Connection Type: Serial Port
Serial Port: Select your current RS485 port
Baud Rate: 38400
Data Format: 8-E-1
Ensure all settings are consistent with those on the GMT-X4.
Click OK to connect.When communication is successful:
The COM1 indicator on the instrument will flash, showing the communication is successful.
The weight value on the GMT-X4 will be consistent with the display on the Modbus Poll software.
That's how you set up communication between GMT-X4 and Modbus Poll through the RS485 port.
In the next video, we will explain how to configure Ethernet communication (Modbus TCP/IP) on the GMT-X4.