New problem, 2 of 11 channels do not respond to input voltages

Question

Hi All, I recently posted a question about my output flat lining, Thanks for all the help.  Since then we thought the problem was gone.  I'm not sure.  We had an applications engineer here on monday morning and she was great.  She re-did our vi front to back and we thought we were in.  Except now two of eleven channels seem to not like us, they pick a voltage point all there own and refuse to read above that point, they just flat line.  The set up for the Daq is as follows: Brand new Dell (bells and whistles) that had one PCI slot available for the new PCI-6224 M-Daq board.  To this we have a SCC-68 accepting signals from a generic 5-B module back plane (all analog grounds are shared).  Into the 5B's there are mixed voltage and current inputs (all modules are matched to the inputs and all output 0-5vDc).  Most inputs work great, two do not.  The new Block diagram uses my pre-defined Task with eleven inputs(mixed) with a couple of empty spaces on the board (i.e.0 is empty, 1-9,12,15 have inputs)  The channels that do not like us are 1 and 7.  The new vi. was built by the appl. engineer using my task and the panel included an indexing array so we can watch all channels at once while the file runs, we also collect data to a .lvm file for later export.  We have tried rescaling the inputs on both the trouble child channels a number of times, we checked the constants for each array and checked the waveform graphs too many times to remember.  If I disconnect these two channels and in put known voltage levels from a calibrator on channel 1 I see a change in signal up to 1.063 volts Dc then it flatlines.  The scaling for that channel was set up numerous times using Linear and Mapping functions in Max.  No difference, even when scaled to only read the voltage input (y=1 x=0).  We did change the Task(i.e. build a new one a number of times and paste it into a copy of the vi. the engineer built for us, no help.  I should mention that I changed all of the inputs at that time to NRSE from RSE (after the problem) because I felt the description of NRSE fit our situation better (High hopes).  All of the channels share an earth ground with their excitation power supplies (I did not set this up, I adopted it and am trying to make it work) and most travel hundreds of feet to the setup.  I do read the voltages that are supposed to be there in the SCC-68 and I do see them vary as they should, but the Daq card doesn't see what I see.  The App's Eng. can't come back soon enough to help us again so I was hoping someone here might have seen this before and be able to set me straight on what I did wrong.  Thanks Rich. 

Answer 1

Hello craftsmanatlarge,
Every time I have seen this bahavior occur, it has been because the input limits of the virtual channel are not correct.  Whenever you create a custom scale for a particular channel, you then have to specify the input limits (max and min) in terms of the scaled units, not the raw voltage.  Please check to make sure that you have done that.  If you are still having trouble after that, please post back with the specific numbers you are using for max and min input limits, and we can troubleshoot from there. 
Best regards,