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Re: How do I set the Relative Air Pressure - calculation?

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  • shanghai_bob_dog
    Hi, I can only work from the absolutes here! 1013.25hpa = 1 atm (atmosphere). The pressure at sea level on a normal day with clear weather and no changes
    Message 1 of 5 , Nov 20, 2007
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      Hi,
      I can only work from the absolutes here! 1013.25hpa = 1 atm
      (atmosphere). The pressure at sea level on a 'normal' day with clear
      weather and no changes taking place.
      So if I take the calculation I made, and apply it on a clear bright
      day... - I am at 1500 feet, or the equivelant in meters. So its
      962.86 ... although someone will probably tell me I'm wrong. :-)

      cheers
      Rob


      --- In wuhu_software_group@yahoogroups.com, "Bill Graves"
      <bill.graves@...> wrote:
      >
      > Now this is where I find a problem with this unit -
      >
      > The unit is reading absolute pressure which is the atmospheric
      pressure at
      > my Altitude 250Ft above sea level(Or so the instructions claim), the
      > Airfield next to us(Also at 250ft above sea level) from which I fly
      is
      > reading a higher Atmospheric pressure than the unit. To set the
      relative
      > pressure to sea level for example I should be increasing by about
      8Hpa(1 Hpa
      > per 30 feet altitude) as obviously there is more pressure at sea
      level.
      >
      > However as I know the unit is not reading the correct Absolute
      pressure and
      > I cannot calibrate it to do so, all I can assume is changes in
      pressure up
      > or down - the accuracy is not good.
      >
      > So what I am saying shanghai_bob_dog is that while your calculation
      is
      > correct for you at 1500m altitude - the pressure would only be
      correct if
      > the absolute pressure you are subtracting from was the pressure at
      sea level
      >
      > So what you have to do is find out exactly what the pressure is at
      your
      > altitude and set this as the relative pressure - ignoring what the
      absolute
      > pressure is saying as this is pre set and will stay fixed relative
      to your
      > "relative" pressure.
      >
      > My head hurts
      >
      > -----Original Message-----
      > From: wuhu_software_group@yahoogroups.com
      > [mailto:wuhu_software_group@yahoogroups.com] On Behalf Of
      wuhu_software
      > Sent: 19 November 2007 15:06
      > To: wuhu_software_group@yahoogroups.com
      > Subject: [wuhu_software_group] Re: How do I set the Relative Air
      Pressure -
      > calculation?
      >
      >
      >
      > Robert,
      >
      > Yes, you need to set the relative pressure on the console itself.
      >
      > Where are you obtaining the relative pressure for your area?
      >
      > Check on Weather Underground for a station that is near you.
      >
      > --- In wuhu_software_ <mailto:wuhu_software_group%40yahoogroups.com>
      > group@yahoogroups.com, "shanghai_bob_dog"
      > <shanghai_bob_dog@> wrote:
      > >
      > > Adding to my first post. I forgot to mention that I am using hPa,
      > and
      > > 1500ft is actually 457.2 meters.
      > >
      > > the atm = 1013.25 hPa
      > > the altitude = 457.2 meters
      > >
      > > Currently my Ws3600 relative pressure is set to 1013.25 -
      obviously
      > not
      > > correct.
      > >
      > > Now, I found a post that gives this deal in imperial
      measurements.
      > > Pressure drops .001 inHg / Foot of altitude
      > > So 1500 feet = 1.5 inHg
      > > and if I multiply this by 33.86 to get hPa = 50.79.
      > > So - I should subtract this from 1013.25, which equals 962.86
      > >
      > > Now this is odd, because the WUHU software is reporting an
      Absolute
      > > pressure that ranges around this.
      > >
      > > So - Do I actually set the Relative Pressure on the WS3600 to the
      > > 962.86 setting - and then everything else falls into place ?
      > >
      > > well - lets suck it and see :-)
      > >
      > >
      > >
      > >
      > >
      > > --- In wuhu_software_ <mailto:wuhu_software_group%
      40yahoogroups.com>
      > group@yahoogroups.com, "shanghai_bob_dog"
      > > <shanghai_bob_dog@> wrote:
      > > >
      > > > I'm trying to figure out just what is meant by setting the
      > Relative
      > > > Pressure setting on my WS3600
      > > >
      > > > I am at 1500 ft abouve sea level. This apparently has something
      > to do
      > > > with the setting.
      > > > The display reads a relative setting and an absolute setting on
      > the
      > > > WS3600. So what should I actually set the devices setting to -
      > > > supposing that I am actually supposed toset it.
      > > > thanks
      > > > Robert
      > > >
      > >
      >
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