Making a vi work?

[philj@digitalpersona.com]

Dell Dimension XPS T850r, Pentium III, with 512MB Ram, running WinXP Pro w/SP 2 and updated all drivers to current ~
Labview installed on C: drive, project and examples files installed on 😧 drive.

Hey I thought that by purchasing Labview 8.2.1 Full Development System Application, installing, running updates, activating the product, and then opening a vi example DAQmx Data Logger to Spreadsheet File.vi, saving a copy, modifying the copy (input a task/select physical channels) and then saving my open files by selecting "save all" would allow me to close that file and open at a later time with saved changes?

What gives? Have I not done something like open new project, create a vi from scratch within the front panel/block diagram that mirrors the example DAQmx Data Logger to Spreadsheet File.vi, check errors, fix, and by selecting run I could generate output data? Do I have to create an executable file which should be compiled/published before putting to use?

I am simply trying to create a vi that acquires analog data from Channels Ai0 and Ai1, called out by task to scale, to write sampled data to a file. At this time I have attached the examples I used, and the renamed files which do not have saved modifications. The data file I took a look at in notepad.

Maybe it's the hardware, a PCI-6250, because I don't know the history behind it here at work if it was abused or not.
I had disconnected any inputs, opened up MAX, ran test panels, I get a flatline signal just like the horizon, flat ~
I have not simulated a PCI-6250 in MAX.

When connecting the input as a differential pairing, a 4-20mA current excitation loop across a 249 ohm precision resistor,
setting up a task to measure analog voltage, setting up a custom scale, "map readings", I have an odd double edged square wave.
Yes the graph chart shows leading edge goes up to "max" end of scale @95 %RH and in 1 smooth line dips down to where it might
be reading voltage level, then dips to low point which I believe is point of sample value, and it's kind of funny looking. I tried to play with sampling rates, 80 samples at 10KHz, 4 samples at 1KHz, etc... but still I have no reading that is a constant voltage/current level.

I backed up and started all over again, creating a task in MAX, defining input as analog - current input, and setting up custom scale.
Min 4mA = 0 %RH, Max 20mA = 100%. I put a profile in the Watlow F4 Controller, ramped to 25C/95%, took measurements after 1 hour stabilizing, and still when I run self test panel, I get an output that looks like oatmeal, all choppy.

I have little experience after going thru the online tutorials (including intro to Labview 6 hours) and I am getting very little done.
It's nice to put something together that works by the end of this week before Memorial Weekend ~

[David S.]

Hi Phil -

While I appreciate the depth of information in your post, I'm not quite sure what the problem is.  I looked at your code, and what's there seems sound.  (It's missing several subVIs, so I couldn't run it myself to test it out.  To post a working copy of your program, you can save the entire heierarchy in a .llb file and post that, or just compress all the VIs as a .zip file.)

What is the expected ouput from the program?  How does the observed behavior differ? Could you post a picture or screenshot of the waveform you're getting? 

I also noticed that you're using sensors that require excitation.  Are you using any signal conditioning equipment (like SCXI or SCC) to deliver the excitation current and read from the sensor?  The DAQ board won't be able to provide a current output, so using sensors without signal conditioning becomes very tedious.