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[wxsig] BP sensor sensivity to heat.

William Beals will at beals5.com
Fri Feb 23 04:27:47 UTC 2007


The routines I implemented do take temperature into account.  The formula is
Where hmvad is the analog output, hmvcc is the sensors VCC, and hmtmp is the
sensors temperature.
That came straight from the datasheet.

Having said that, I do assume that the humidity sensors temperature is the
same as the DS2438s.  Any chance that you are heating one sensor a lot more
than the other with the regulator?


-----Original Message-----
From: wxsig-bounces at lists.tapr.org [mailto:wxsig-bounces at lists.tapr.org] On
Behalf Of wn0x at earthlink.net
Sent: Thursday, February 22, 2007 7:59 PM
To: wxsig at lists.tapr.org
Subject: [wxsig] BP sensor sensivity to heat.


I have a version 3.0 Atkin/Bray BP sensor

This is that last version with the surface mount construction.  When placed
in an enclosure with a very warm 7805 (12 volts to T238+), the BP
consistently reads about .10 inHG higher than it should.  After removing the
back cover of the enclosure the BP returns to normal. Placing my finger on
the DS2438 raises the BP reading as well.

Any ideas?  Is my DS2438 sensitive to heat?  I didn't think that the T238
considered temperature when calculating BP, even though some of the formulas
I found consider temperature.


Rich wn0x/ap006

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