How do I connect a Rosemount 3051T Pressure Transmitter to a Modicon Micro 612-03 PLC

[ShaunH]

Hello, I am entering the final stages of the PLC program using a Modicon Micro 612-03 I used a loop calibrator (4-20mA) to simulate the pressure transmitter before connecting it up to see if the program is working correctly.

Once I proved that the program was working correctly I connected the pressure transmitter up by providing an external power supply (24v) and also connected the loop which goes to the PLC to the device as well.

when i operated the system I was getting 4095 on the analog input which I believe to be full scale, which is not what it should be.

Im not entirely sure about the wiring which I have done I have been told that there needs to be a resistor put in the loop to control the input loop current at 4-20mA. But from looking at the PLC where the analog connects to internally there is a 250 ohm resistor??

Please help

 

[danw]

If you didn't need a resistor for the current simulator (loop calibrator), you don't need one for the real thing. Yes, a resistor is needed on an analog input, but the resistor is likely built into the analog input in your case.

You need to review how you wired the power supply in the loop with the transmitter and the analog input

Pay no attention to the colors, but pay particular attention to the polarity of the connections. Your PLC is the 'instrument'. The Rosemount is the xmtr.

 

[ShaunH]

Ah okay ill give that a go, then would i take two seprate wires for the loop to the analog input. or are the connections to the plc the analog inputs?

 

[danw]

Your PLC's analog input is labeled "instrument" in the diagram.

 

[ShaunH]

Okay cheers that makes sense now ill give that a go and let you know how it goes