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frenchy

My IF2OF2 analog input isnt doing full scale....?

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Hello, I am using an IF2OF2 analog IO module in conjunction with a Micrologix 1100. I have both analog inputs set up for voltage mode with raw resolution. I thought I should expect 0v = 0counts and 10.5v = 32760 counts.... but, when I use a power supply to feed a test voltage into the analog inputs, I am seeing a maximum of 32672 counts on both inputs with an input voltage of approx 10.57 volts. The counts never rise above 32672 even when my input stimulus is up to 10.8v. Why are my modules "capping out" early? So, when I set up my SCP functions in RSLogixMicro, should I use the "truth" or the expected? Truth = 0-10.5v = 0-32672counts, so 0-10v should be 0-31116counts. Expected = 0-10.5v = 0-32760counts, so 0-10v should be 0-31200counts. My gut tells me to use the truth, but someday the IF2OF2 might wake up and do its job properly! Thanks for any input! Respectfully, Steve French 814.584.1220.office 814.730.0003.cell President, Volt Vision www.voltvision.com Edited by frenchy

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I have a 1762-1F4 4 channel analog input card with my 1100 but I use 4-20ma as my (Raw) signal current. If I'm following you correctly, you said you are feeding 10.50 Volts DC into the analog card and generating a count of around 32672? That part seems correct to me (maxing out) Or is this a variable power supply you are using (From 0-10V dc) and no matter what the voltage is you are not showing any (Counts) change? Make sure you have the 0Vdc common tied into "Say" input 0- of the analog card and your +Vdc (up to 10Vdc max) into input 0+. You should be able to show the "Raw" data just by putting in a MOV command in your logic and setting the source as I:1.0 assuming your analog card is in slot 1 of the rack and destination as "N7:0 for an integer register. So as an axample (0Vdc= 0 Counts.) (5Vdc =16336 Counts) (10.0Vdc= 32672 Counts) Hope some of this helps ya... Edited by splicer480

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Hello Splicer, thank you for your response. It indeed is a variable power supply that I am using as my test input (it will go up to 30vdc or so, but for this test I havent exceeded 11vdc for fear of damaging the IF2OF2 input). The "maxing out" is happening @ 10.5v (not 10v) and I am fine with that....what I am not fine with is that the counts never get to the specified 32760. They are stopping @ 32672. Is this normal? Are all modules different and you have to "see" what it really does? Is it like a car thats rated to go 200mph, but mine only goes 195? So running my new car @ 100% doesnt really mean 200, it means 195? thx, frenchy
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0-10.5 volts is correct by the specification. I don't understand the counts difference though. That seems very odd. Have you checked the configuration word? I suppose nothing in your program is limiting it... Are the over range flag bits coming on? Edited by finfin

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I don't have my micro 1100 in this plant but if I remember correctly when my current was @ 20ma my count was right around 32672 and when it was at 4ma my counts were something like 3000. Not the 00000 I thought it would have been. I used the SCP (scaling with parameters) to clean it up a little and get the counts a little tighter for my application. So, basically I used what the laser measurement sensor (Allen Bradley 45CPD) and analog card provided me with and went with that.

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Yeah the Current threw me off at first too. but a lower high end makes sense in that case because the spec'ed current range is 0-21 ma.

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