SM 331 - 2 wire current measurement problem

Hi,

I have trouble with using SM 331 (6ES7 331-7KF02-0AB0) for 2 wire current measurement. My configuration consists of a power supply (PS 307 / 10A), CPU315-2 PN/DP and a SM331 analog input module with a GEMS 3300 Series pressure sensor (0-1 bar measurement range) connected to CH1.

CH0, on SM 331, is not in use. I connected a 3.25kOhm resistor to this channel, in order to maintain the diagnostic capability of channel group 0. This was recommended by several sources.

A wiring diagram is attached to make it clear.

I experience following:

I switch on my system and everything seems to work properly. Green status LEDs everywhere etc. TIA (V13) gives me no warnings / errors. I'm using a multimeter to measure a current in the loop, as indicated in the wiring diagram; I'm reading 4 mA (0 bar) on the multimeter display with no pressure applied. In "Default Tag Table"  CH1 is rep. as; Name: 13-PT-007, data type: int, address: %IW258. In "online" mode a "Monitor value" pops-up which shows "0". So far everything behaves as expected..

However, when I start to increase the pressure, nothing happens with the "monitor value". It says "0". I can see that my pressure sensors works since I am reading 5.37 mA on the multimeter display when pressure increases.

I tried to look for solution in different manuals covering SM 331 wiring, setup and recommended practice, with no success. 

Is my wiring done right??

Any suggestions??

Thank you

hi,

have you tried to access with "%IW258:P" for peripherial access? You need to do it like that when the adress is not in the process image. 

hope this helps,

reagards,

And you should also try to set the data type WORD instead of INT.

nice regards

Hi mopS04,

Thank you!! Problem solved:) 

I will dig into details on this topic; any manuals you recommend??

Again, thank you for your help.

Kampi

And you should also try to set the data type WORD instead of INT.

nice regards

 Hi Kampi,

I tried that; same result.

Anyway, thaks for the feedback.