Analog Input 1794-IF4I over DH to PLC5/40

Hi all,

I have a current transducer set up on a motor wire providing 4-20 mA output into a 1794-IF4I module. The wiring seems good thus far, but I'm developing the logic. Since the PLC rack goes over Data Highway to a 1771 rack, I'm stuck with scaling the input in RSLogix5. Here is the problem:

We have a BTR set up since all I'm interested is the current feedback from the motor wire. In the BTR block, I set up the Data file to N7:0 (seeing that the input will be a range from 0 - 32,768). Now, when I look at my N7 data file, in N7:5 I see "-32768". I'm not sure why it's a negative value and why bit 5.

Ideally, I'd like to scale the value I'm getting from 0 - 5 Amps. I have the calculations I need to perform, but have to get past this data reading.

Any suggestions/advice?

Thanks.

Firstly, you must be communicating over RIO, not DH.

You have to configure the module by sending data via BTW.
You can do this the hard way by studying the manuals and creating the necessary data files and program. Or, you can let RSLogix do it for you - enter the module in the processor's I/O configuration, double-click on it, then fill in the blanks and let RSLogix create the ladder rungs - all pretty painless.

RSLogix will automatically create the BTW/BTR logic? Will the data be stored in N7?

yes

abs014000 said:

RSLogix will automatically create the BTW/BTR logic?

Click to expand...

yes, in the ladder file of your choice

abs014000 said:

Will the data be stored in N7?

Click to expand...

That is one of the blanks you have to fill in (where to put the data)

Thanks for your answers. I am able to get the readings now.