New Engineering Units Beta Software Going Once…

7 Comments

1. 
   George Bynum
   Posted June 9, 2012 at 12:34 pm Permalink

   I only use my Dataq system about once a month, so I’m not really a good reference point.

   I copied the browser software and played with it a little. I’m SLIGHTLY puzzled by what it is doing, or more accurately by what it does relative to F12 settings.

   I used a pressure transducer, 0V=0psi, 10V=6000 psi and enter into fixed calibration (device that is bipolar only) high=6000, low=-6000

   The current flow in cabling has introduced voltage drop resulting in an offset 0 where I’m seeing -10 psi at atmospheric connection.

   If I use engineering unit offset of 10, display looks good, but fixed calibration shows 6000 and -5990 which has changed the slope PSI/volt(totally inconsequential with accuracies and resolution involved, it is the concept which concerns me)

   I noticed this when I wanted to change to bar for a report; the OEM has all nominal values in bar. It was when I went to enter 414 and -414 that I noticed the 5990 …

   I don’t know when I’ll have a chance to hook up one of my position transducers (I use several varying from 2 inch stroke to 240 inches) and where “redefining” zero will be useful; as of now, I use Advanced CODAS at the report generation stage, ignoring the screen values during acquisition.

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2. 
   DaqGuy
   Posted June 11, 2012 at 8:42 am Permalink

   George,
   Thank you for your comment. I’m a little confused by your question and I attempted to duplicate your results without success.

   First, I assume that you understand that the new EU settings menu will replace the Fixed type that you accessed using the F12 short-cut key.

   Next, I attempted to duplicate your experience by calibrating a channel for ±6000 PSI using the old Fixed method. Then I used the new EU Settings menu to remove an offset of 67.4. When I then accessed the Fixed Cal method to see how the calibration values had changed, I saw that both the high and low cal values changed by exactly the same amount. Each was 67.4 units lower that initially defined. The new high value was 5932.6 and the new low value was -6067.4. This indicates that the slope had not changed, but that the calibration line had shifted to a new Y intercept, exactly 67.4 units lower than before.

   Can you provide more information to help us duplicate what you saw, or try applying the above process to see if you can duplicate our results?

   Thanks

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   • 
     George Bynum
     Posted June 11, 2012 at 11:04 am Permalink

     ok, I took a real file and extracted a small part or it, 8k. I use a screen capture app to get the screen sections involved. Total is about 220k, zipped 128k; will DaqGuy at dataq get to you?

     I carry a range of pressure and stroke transducers. The offset might be reliably stated to never be known before connecting … which cable and number connected will offset zero.

     I’ll assume my 6000, initially entered 6000 and -6000, thus 12000 psi per 20V

     I show -3.3 after A for open condition, so go to EU and enter a 3.3 offset.

     Back to look at F12, shows 6000 and -5993.4

     I don’t know how to post here, but can in support forums if you want to see them. Oh, WinDaq 2.77 …

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     • 
       DaqGuy
       Posted June 11, 2012 at 11:57 am Permalink

       George,
       If you have screen captures to post then it would be better to use the support system: http://www.dataq.com/ticket.

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       • 
         George Bynum
         Posted June 11, 2012 at 9:46 pm Permalink

         done … first time I’ve ever used the Support Center.

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     • 
       DaqGuy
       Posted June 11, 2012 at 1:24 pm Permalink

       I assume that you’re using the new EU Settings dialog box to define the relationships between volts and EU, as well as to define the offset?

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       • 
         George Bynum
         Posted June 11, 2012 at 9:37 pm Permalink

         not using EU to define relationship … will try that … only to apply offset. Use F12 to do initial scaling.

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