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Analog inputs-Snap and expansion modules

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Now iam working with naked V570 HMI and v200-18-E4XB snap module + expansion module IO-ATC8.



I got some problems with IO-ATC8 analog inputs. 



In my setup iam use  current transformer http://www.ecproducts.co.uk/productdetail.asp?cat=24&item=4&pid=2135. 



Current transformer output is 4-20mA , so IO-ATC8 range of data iam  using is 3277-16383 hardware configuration "normal mode", tumbler settings for current aquistion.



My goal is show current value in HMI display, but there are some probems. Real values i getting is  2027-4323 ( these numbers not evry time the same).


One time after restart of PLC  ( power on/off) i saw good range  3277-16383. But after another restar input values changed  2027-4323.




I dont know what to do, because same type transformer working in another el. cabinet, it connected to HMI snap input, range 819 to 4095. It works but some times snap input not working properly ( after resets), then i need turn of plc and wait, after aproximetly 30min input starts work fine. Hardware setting adjusted for current input.



I measure transformer output it works fine.



Waiting for Help.


Best regards,





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I would suggest putting an electrical meter in line with your CT and make double sure that you are actually putting out a 4-20ma signal and not something less.  I use IO-ATC8 modules and CTs all the time.  I tried to look up your CT but the link shows to be broken and was not able to see any information.  Looking at the specs for the CT is says "nominal 24VDC required"  It is entirely possible that when connected to the ATC8 the voltage in the loop is falling below your CT required minimom voltages.



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