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I need to show a voltage on a remote LCD display that has a 0-10v input. I am sending the value via the V200 analog output, set up as 0-10v. With the LCD disconnected, I get the 0-10 volts from AO0, but when I connect the LCD to the AO0 port, the LCD displays approx. 500 mv. and the output of AO0 drops from 10v to about 3.2v. The LCD datasheet says the the IN1 input is not isolated from the V+ ground.


I am guessing that this is because I have not connected the Analog Output COM line, and the voltage from AO0 has no return path;

The question is, if it is OK to connect the COM line to the 0V common? This type of connection is not shown in the V200 documentation.


Thanks for any help in this matter.




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When connecting an analog output, the COM line is required for proper operation. The wiring diagram for the V200-18-E3XB can be found within the specifications sheet on page 7.


I have also attached the wiring as shown below:


V200 18 E3XB Analog Output


Is there also a COM line on the LCD display? Can you provide a manual for the analog input wiring for the device?

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The LCD has a 0V terminal, V+ , IN1 and IN2 (2 analog 0-10VDC inputs).


Can the V200 analog COM line be safely attached to the 0V line, or does it need to remain isolated from the power ground?


Thanks for the help...


Attached is the connection diagram in the LCD's datasheet;

Pages from data logger0366543001389873036(1)

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There is a note that the +V, IN1, and IN2 of the LCD all share the same 0V common. I cannot guarantee any safety since it is not a Unitronics product, but as long as the PLC and LCD are using the same power supply the COM and 0V lines should electrically be the same.


I do also want to point out that we do not support loop powered devices, so if the IN1 and IN2 of the LCD require additional power for the hardware, the could also be the cause of any issues.

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