when aid150 is in use, the total number of Insulation Monitors and residual current monitors
connected to RS485 bus should be set first, and the total number should not exceed 16 sets. This
parameter is in [communication settings] in the menu. The slave address of each insulation monitor
and residual current monitor shall be numbered from 1 to 16 as far as possible. When the total number
of Insulation Monitors and residual current monitors exceeds 16 sets, the number of aid150 shall
be increased and networking shall be conducted separately.
7 Communication protocol
7.1 Modbus-RTU communication protocol
In five pieces of products, the communication between the AIM-M10 insulation monitor and the upper
computer uses the Modbus-RTU communication protocol. The Modbus protocol particularly defines the
check code, the data sequences and so on, which are the necessary contents of the specific data
exchange. The Modbus protocol uses a master-slave responsive connection (half-duplex) on a
communication line, which means the signal on a single communication line is transmitted in two
opposite directions. Firstly, the signal from the main computer is addressed to a unique terminal
device (slave computer), and then the answering signal emitted from the terminal device is
transmitted to the host in the opposite direction.
The Modbus protocol only permits communication between hosts (PC, PLC, etc.) and terminal devices,
without allowing the data interchange between independent terminal devices. So that terminal devices
do not occupy communication lines when they are initialized and are limited to in response to the
query signals arriving at the computer.
7.2 Introduction to the function code
7.2.1 Function code 03H or 04H: Read the registers
This function allows the user to acquire the data collected and recorded by equipment and the system
parameters. The number of data requested by hosts has no limit, but cannot exceed the defined address
range.
The following example shows how to read a measured insulation resistance value from No.01
slave
computer, with the address of the insulation resistance value of 0008H.
The host computer
sends
Send
message
The slave computer
returns
Return
message
Address code
01H
Address code
01H
Function code
03H
Function code
03H
Start
address
High
byte
00H
Bytes
02H
Low byte
08H
Register
High
00H