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## Re: [Paparazzi-devel] Booz Barometer R1, R2, and Rs Values?

 From: Jayson MacKiddie Subject: Re: [Paparazzi-devel] Booz Barometer R1, R2, and Rs Values? Date: Sun, 28 Feb 2010 19:24:58 -0500

Hello Poine and David,

Thank you! Poine, do you have values for R38, R39, and R40 in the adjustable voltage referance circuit to the -VREF terminal of the ADC? Or do I need to determine an appropriate value according to the MPX 6115 output at our altitude. I'd be happy with a value you're using at the moment and we could tweak things once we get ourselves flying.

Regards,
Jay

On Sun, Feb 28, 2010 at 6:18 PM, antoine drouin wrote:
Hello

There is a little scilab script  (
paparazzi4/trunk/hw/booz/baro_amp.sce ) which you can use to play with
the values of the resistors.

The values on the schematics, ie
R10 = 27e3;
R5  = 390;
R6  = 12e3;
R20 = 560;
R21 = 680;
gives you an altitude range of -500m:930m ( with ground pressure at
1013 ) which is a bit silly

You might want to lower R20, for example
R10 = 27e3;
R5  = 390;
R6  = 12e3;
R20 = 220;
R21 = 680;
gives you an altitude range of -380m to 1530m which is a bit better (
you want the negative value if you want to be able to fly at sea level
on a high pressure day )

There is a slightly better script in
paparazzi4/trunk/hw/lisa/pressure.sce which takes sea level pressure
into account ( the one in booz doesn't, feel free to improve it )

Regards

Poine

On Sun, Feb 28, 2010 at 9:28 PM, Jayson MacKiddie
> Hello all,
>
> We have decided to add the booz barometer to our Booz main boards. We have
> the parts list but what are the values of R38=Rs, R39=R2, and R40=R1 in the
> adjustable voltage referance circuit to the barometer? Are they to be
> specified based on local altitude to take full advantage of ADC resolution?
> Regards,
> Jayson MacKiddie
>
> _______________________________________________
> Paparazzi-devel mailing list
> http://lists.nongnu.org/mailman/listinfo/paparazzi-devel
>
>

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