Chengdu Ebyte Electronic Technology Co.,Ltd. ME31-AAAX2240_UserManul_EN
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Configured as 0: means 0～20mA
Configured as 1: means 4～20mA
【Note】AI configuration instructions
(1) The AI sampling range is shared by all channels. When the AI channel sampling range is configured as
4-20mA sampling, if the current signal is lower than 4mA, the engineering value of the channel will be converted to
0. There is no conversion limit for signals greater than 20mA, but cannot exceed 25mA (more than 25mA will
cause equipment damage).
(2) The AI channel sampling range parameter address is 0x04B2, the register type is a holding register, and the
function codes are 0x06 and 0x10. When writing the sampling range parameter of the AI channel, if the written
parameter value is not within the range of 0 to 1, it will automatically take the closest value and write it. If the
writing sampling range parameter is 2, the device will take 1 as the sampling range parameter. And Modbus does
not return an error command.
4.4.2 AI original value and engineering value of analog input
There are two ways to read the magnitude of the current signal collected by the device:
(1) Read the original value of AI, and calculate the input current according to the input impedance. The AI
original value register address is 0x0000～0x0003, the register type is input register, and the read function code is
0x04. The value returned by this method is 2 bytes representing a channel, and the range of the read value is 0～
4095. The method of calculating the current size is that 0～ 4095 corresponds to 0 ～ 25mA. The register type is
discrete input register, and the read function code is 0x04. which is:
Current = （original value× 25）/4095 (mA)
(2) Read the AI engineering value and directly convert it to obtain the input current. The AI engineering value
register address is 0x0064 ～ 0x0067, the register type is input register, and the read function code is 0x04. The
value returned by this method is 2 bytes representing 1 channel, and the read value ranges from 0 to 25000. The
method of calculating the current size is 0～25000 corresponds to 0～25mA. which is:
Current = original value / 1000 (mA)
4.4.3 Input filter parameters
The filter parameters of the AI channel can be set. The valid values are 1-16, and the default value is 6.
Filter parameter description:
(1) All AI channels share one filter parameter. The higher the parameter value, the more stable the output value
and the slower the response.
(2) The AI channel filter parameter address is 0x04B0, and the register type is a holding register. Function code
0x06, 0x10.
(3) When the AI filter parameter is written, if the value of the parameter to be written is not within the range of 1
to 16, it will automatically take the closest value and write it. If the write filter parameter is 0, the device will take
1 as the filter parameter, and Modbus does not return error commands.
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