Bad readings when another channel maps ranges

[John Hoard]

Two channels read about half correct voltage, but only if another channel (several A/D channels away) is set to Map Ranges with correct values. If set to Map ranges with defaults, or No Scaling, then the channels read correctly. This is verified in two different applications reading the same channel list.

[mhaag]

It is a little hard to figure out what exactly might be going on with the information provided. What application are you testing this on? What version of NI-DAQ do you have installed onto your machine? Are you using virtual channels for all of your inputs?

Using the test panels on my machine, I was able to play around with the Map Ranges setting in Measurement & Automation Explorer (MAX) but was unable to duplicate the results that you are seeing. I would be sure to verify that your virtual channels are indeed referencing separate channels and that the settings are being saved and set as you would expect. Do you see these results in the Test Panels in MAX?

I was not able to find any report of this type of phenomenon happening so hopefully it is just a set
ting that we are overlooking on your system. If you are still having this problem, then provide a little more information and we can see what we can do. Thank you!

Regards,
Michael H
Applications Engineer
National Instruments

[John Hoard]

I made a simple program to read four virtual channels using AI One Scan. With the last of these set to No Scaling in MAX, everything works right. With the virtual channel set Map Ranges (0-5 volts ==> 0-2000ppm) it works. With scaling (0.32-5 ==> 0-2000) it reads the first two channels wrong. With this same setup, trying to read any channel from MAX gives a 10680 error. A workaround was to set scaling to (0-5 volts ==> -127-2000ppm) and everything works. This sounds a lot like a software "undocumented feature"! I have emailed my .daq and test program to NI (service ID 7029559).