On 30.6.20 20.11, R.Wieser wrote:
> Hello all,
>
> I've bought a BMP180 barometric pressure sensor and used an existing
> implementation of the conversion formule (as in the PDF mentioned below) to
> see it work.
>
> The problem is that the air pressure result is (currently) about 8 full
> points off from what I could find on the 'Web that it should be.   The
> resulting temperature is in the middle of  two other (though not as precise)
> thermometers, and therefore looks to be ok.
>
> I've made sure that the calculation is correct by taking the calibration, UT
> and UP values straight from the PDF here:
>
> https://cdn-shop.adafruit.com/datasheets/BST-BMP180-DS000-09.pdf
>
> pull them thru the calculation and getting the exact intermediate results as
> well as T and P values back as shown in the PDF.
>
> My question:
>
> Is the sensor supposed to be able to give that different results (internet
> shows 1008, 1009 hPa around my position, the sensor shows 1000.47) ?    I
> thought that the calibration process and resulting data would not allow for
> it ?    What might be causing it ?
>
> Regards,
> Rudy Wieser


The air pressure decreases around 1 hPa / 27 ft of altitude at surface
altitudes. Are you at sea level?

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-TV

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