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Entry  Thu Nov 29 17:46:43 2018, gautam, Update, General, Some to-dos 
    Reply  Fri Nov 30 15:53:52 2018, Jon, Omnistructure, General, N2 pressure gauge fix N2_transducer_datasheet.pdf
       Reply  Tue Dec 4 18:24:05 2018, gautam, Omnistructure, General, N2 line disconnected IMG_7195.JPG
          Reply  Thu Dec 6 17:33:33 2018, Jon, Omnistructure, General, N2 line disconnected 
Message ID: 14325     Entry time: Fri Nov 30 15:53:52 2018     In reply to: 14324     Reply to this: 14331
Author: Jon 
Type: Omnistructure 
Category: General 
Subject: N2 pressure gauge fix 

I've made a repair to the N2 pressure monitor. I don't believe the polarity of the analog signal into the controller actually was reversed. I found the data sheet (attached) for the transducer model we have installed. Its voltage should read ~0 at 0 PSI and 100mV at 100 PSI. As wired, the input voltage reads +80 mV as it should.

The controller calibrates the sensor voltage to PSI (i.e., applies a scale and offset) based on two settable reference points which appeared to be incorrect. I changed them to:

  1. 0 mV = 0 PSI (neglecting the small dark bias)
  2. 100 mV = 100 PSI

After the change, the pressure reads 80 PSI. Let's see if the time history now shows a sensible trend. 

Quote:

[koji, gautam, jon, steve]

  • We suspect analog voltage from N2 pressure gauge is connected to interfacing Omega controller with the 'wrong' polarity (i.e pressure is rising over ~4 days and then rapidly falling instead of the other way around). This should be fixed.

 

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N2_transducer_datasheet.pdf
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