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[wxsig] BP sensor sensivity to heat.

wn0x at earthlink.net wn0x at earthlink.net
Sat Feb 24 00:42:51 UTC 2007


Will,

I am using the DS18S20 on the X1W board for temperature, which is place outside.

Rich

-----Original Message-----
>From: William Beals <will at beals5.com>
>Sent: Feb 22, 2007 10:27 PM
>To: wn0x at earthlink.net, 'TAPR Weather Station SIG Mailing List' <wxsig at lists.tapr.org>
>Subject: RE: [wxsig] BP sensor sensivity to heat.
>
>Rich:
>
>The routines I implemented do take temperature into account.  The formula is
>hmval=(((hmvad/hmvcc)-0.16)/0.0062)/(1.0546-0.00216*hmtmp)
>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?
>
>will
> 
>
>-----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.
>
>Gentlemen,
>
>I have a version 3.0 Atkin/Bray BP sensor
>(http://www.simat.org.uk/barometer.html). 
>
>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.
>
>Thanks,
>
>Rich wn0x/ap006
>
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