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

[antoine drouin]

digikey : MPXH6115AC6T1CT-ND

On Mon, Mar 1, 2010 at 1:56 AM, Jayson MacKiddie
<address@hidden> wrote:
> Hello Poine,
>
> Much obliged! :) Thank you. Could I trouble you for an MPX 6115 part number?
> There are many options in the series and I'd like to make sure I've got it
> right. I've narrowed it down quite a bit, but I'm probably better off just
> asking.
>
> Regards,
> Jay
>
>
> On Sun, Feb 28, 2010 at 7:41 PM, antoine drouin <address@hidden> wrote:
>>
>> Don't populate the 24 bits ADC (U$9) and associated parts ( R38, R39,
>> R40, U$10, C33, C34)
>> We use the LPC2148 internal ADC, hence the variable offset amplifier
>>
>> On Mon, Mar 1, 2010 at 1:24 AM, Jayson MacKiddie
>> <address@hidden> wrote:
>> > 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 <address@hidden>
>> > 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
>> >> <address@hidden> wrote:
>> >> > 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
>> >> >
>> >> > _______________________________________________
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>> >> >
>> >> >
>> >>
>> >>
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>> >
>> >
>> > --
>> > Jayson MacKiddie
>> >
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>> >
>>
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>
>
> --
> Jayson MacKiddie
>
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