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Tuesday, September 25, 2018
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Sepam output 4-20 mA with PLC
Reading Sepam S42 4-20 mA with PLC

Hi,
I want to transmit the 4-20mA output of Sepam S42 to a PLC. What I understood from Sepam manual is to use the MS 141 communication module and the Modbus RS 485 2 wires interface and configure the relay by entering the parameter to be converted to 4-20 mA and the min and Max corresponding to 4-20 mA.

Is that correct? What are the hardware requirements?

Thank you

No, you do not use any RS-485 communication module for a 4-20mA output signal. 4-20mA is an analog signal which uses the MSA 141 analog output module

Your statement, "to use the MS 141 communication module and the Modbus RS 485 2 wires interface and configure the relay by entering the parameter to be converted to 4-20 mA and the min and Max corresponding to 4-20 mA" would be correct by taking out the reference to Modbus RS 485:

"to use the MSA 141 communication module interface and (in the configuration) enter the parameter to be converted to 4-20 mA and the min and Max corresponding to 4-20 mA."

The MSA 141 module and its setup is described on pages 238-239 of the S40 manual at this link:

https://tinyurl.com/yb7b7o5a

The 4-20mA is an active, powered output.

Some kind of cabling with RJ-45's is required to connect the option module to the main S40 device.

The PLC requires a 4-20mA analog input and the resources to configure the input and do something with the data.

Thank you David,

So I need RJ45 between Sepam and MSA 141. But what about the cabling between the PLC and the MS141? What type of wire ,section, etc.?

The distance between Sepam and PLC is around 60 m.

The Sepam manual gives part numbers for digital connecting cables (RJ45). I have no idea whether those cables are conventional Ethernet cables or not.

The analog output signal connection from the options board to the PLC analog input can be any shielded twisted pair cable. Whatever the other analog inputs to the PLC use.

I don't care to use Ethernet CAT5/6 cable because the 24g conductors are so fragile; I prefer heavier gage (20g) copper conductors, but it will work.