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LPS25HB Temperature Compensation Behavior

Question asked by KJD on May 9, 2016
Latest reply on Jun 16, 2016 by walker.dave
My colleagues and I are evaluating the LPS25HB and came across some behavior we don't understand. There are two issues we are trying to resolve right now:
  • Embedded temperature compensation behavior is confusing.
  • Accuracy isn't what it should be.
  • In one of our datalogs (pressureLog_25Hz.xlsx) we see absolute pressure tracking with temperature. We expected temperature to change, but not absolute pressure. Absolute pressure is changing at a rate of about 3 hPa/C. Shouldn't the embedded temperature compensation deal with this?
  • In a test we did in a car (car pressure log.xlsx), we saw temperature drop and then increase, but the pressure is almost constant if you draw a trend line through the data. It seems like embedded temperature compensation is doing something this time.   
    • We need help determining why is the sensor acting differently.
  • The datasheet for the part claims an absolute accuracy of +/-0.2 hPa between 20 and 60 C. So far, the data we have taken from the sensor does not meet the spec. For example,    
    • I a recent test, our local weather stations reported a sea level pressure of 1016.2 mbar.
    • The LPS25HB evaluation kit is told us the absolute pressure was 1026.5 mbar.
    • We are about 160 above sea level, which equates to a pressure difference of -6 mbar, so the LPS25HB should have reported about 1010 mbar. It was off by 16.5 mbar!
Thanks for the help!