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Sunday, May 27, 2018
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Unit ID
Unit ID of SDM120 Power Meter


I am a newbie in modbus. How can i change unit id of sdm120 meter? Do i need to use software or program or something like that?

Please help


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When you're a newbie in any field, it pays to read the manual.

The manual here:

says, "Click the button, the LCD display will scroll the measurements. Keep pressing the button for 3 seconds, the meter will get into set-up mode."

page 5 shows the Modbus and serial settings.

Hello David 2,

I know that when users press the bottom for 3 sec, lcd display "set". So user can program the meter parameters by sending correct command via 485 port. But you know i don't know how to program and how to send command. That is why i ask.


I'm in that group of people who mess with Modbus who like external serial setting devices, like DIP or rotary switches or jumpers. But this unit does not have that. But most Modbus devices allow for firmware changes through a setup mode.

I don't have a unit to play with, but my guess is that the reason for the set-up mode is so that the serial connection settings can be changed without requiring a Modbus connection using the default settings. I could be wrong and this could be one of those horrible Modbus devices whose settings can only be changed via a serial connection.

Try going into the setup mode and try to discover which button scrolls from parameter to parameter, and which button changes the the parameter's setting from one setting to another setting.

Be advised that many, if not most, devices fail to recognize serial setting changes until the DC power is cycled on-off to the device. SO be sure to cycle the power after changing the serial settings.