Jeff164 Posted December 14, 2021 Report Share Posted December 14, 2021 Maybe this is a dumb question...but I'd rather ask than make an even dumber erorr. I'm familliar with discrete inputs, and that they can be sourcing or sinking. Typically I use a Sourcing input and the modulating analog signal (postive voltage, current flow going into the PLC input) is then dropped across an internal load in the PLC and is shunted to the 0 volt reference on an internal buss of the PLC. I've never heard the term applied to an analog input before - but to me, they would also be sourcing inputs, and function in a similar manner. I have a new transmitter to work with and its a 3 wire 4-20 signal. Tech literature with the transmitter shows that it is selectable to be configured for a sourcing or a sinking analog input. I dont see anything in the installation guide of the PLC other than the jumper 12 for selecting sourcing / sinking discrete inputs and the other jumpers for configuring the analog inputs. The diagram in the install guide to me looks like the analog input would be termed as "Sourcing" and that the load resistor is internal to the PLC. I've wired these sucessfully before - Just never came across anything describing an alalog input with these terms. PLC in question is a SM70-J-TA22 thanks Quote Link to comment Share on other sites More sharing options...
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