7ML19985FH03 SITRANS LR 400 ñ INSTRUCTION MANUAL Page 23OperationThe electrical connection of the PC/Laptops and the HART-Communicator to the 4-20-mAsignal cable is shown below.Connection, HART Schematic DiagramThe connection of the PC/Laptops and Profibus-PA to the 4-20 mA signal cable is shownbelow.Connection, Profibus Schematic DiagramNote: A 250 ohm loop resistor may be required, depending on PLC input resistance.Warning: The coupling module (shown below) may not be used in areaswhere there is an explosion hazard and may not be connected tointrinsically safe circuits.PLC with mAinput cardHARTHART Communicator 275SITRANS LR 400PC/laptop with HARTmodem running PDMPDM Class 2MasterClass 1Master PLCDP/PACoupler ET200HARTProfibus-PASITRANS LR 400 SITRANS LR 400 SITRANS LR 400