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'[EE] Atmospheric Pressure Ranges'
2005\05\31@161051 by Mike Hord

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I'm trying to get a feel for the "normal" range of atmospheric
pressure.

Wikipedia tells me that the highest and lowest ever recorded
barometric pressures are 108.57 kPa and 86.996 kPa,
respectively.  It also tells me that "standard" atmospheric
pressure is 101.325 kPa.  What it does NOT tell me (nor
does anywhere else) is what the "normal" range is; that is,
if a good, strong thunderstorm passes through, what can
I expect the pressure to be?  Likewise, in a typical high
pressure area, what can I expect the pressure to be?

I'm trying to develop a water depth gauge, and if possible,
I'd like to get some feel for the variation of pressure based
on atmospheric variations.  The highest to lowest cited
above would represent a 2.2 meter(!) fluctuation in the
depth of a body of water, if one were basing the depth on
the pressure at the bottom.  Needless to say, that
kind of variation would render the information useless.

Normal diurnal cycles are <.5 kPa, which corresponds
to approximately 5 cm of water depth.  No info on
typical changes outside those variations, however.

Differential measurement is NOT an option for this
application.

Mike H.

2005\05\31@164915 by PicDude

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On Tuesday 31 May 2005 03:10 pm, Mike Hord scribbled:
> I'm trying to get a feel for the "normal" range of atmospheric
> pressure.
>
> ...
> Differential measurement is NOT an option for this
> application.

Bummer -- I was thinking of differential as I was reading this message.

You might try contacting an aviation FSS (Flight Service Station, where
general aviation and other pilots get weather reports).  They are usually
great about helping out with stuff like this.  Find a small airport in your
area and call any FBO there for the nearest FSS.  You can walk in and chat
with them about it.

Cheers,
-Neil.



2005\05\31@170318 by Mike Hord

picon face
> > I'm trying to get a feel for the "normal" range of atmospheric
> > pressure.
> >
> > ...
> > Differential measurement is NOT an option for this
> > application.
>
> Bummer -- I was thinking of differential as I was reading this message.

Yah, that'd make things MUCH easier.  However, the item in question
must be self-contained and could be at reasonable depth.  It should
also be as near to idiot-proof as possible, or at least VERY easy to use.

> You might try contacting an aviation FSS (Flight Service Station, where
> general aviation and other pilots get weather reports).  They are usually
> great about helping out with stuff like this.  Find a small airport in your
> area and call any FBO there for the nearest FSS.  You can walk in and chat
> with them about it.

This is a good idea; ask someone who regularly pays attention to it!
Although I had hoped at least one such person would be reading the
list today...;-)

Mike H.

2005\05\31@170709 by Dave VanHorn

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face

>
>Differential measurement is NOT an option for this
>application.

Hmm.. Why not?
Push some air down a line that goes to the bottom, and it will max
out when you start bubbling.
Pout - Pin and you're there I think.


2005\05\31@171236 by Denny Esterline

picon face
> I'm trying to get a feel for the "normal" range of atmospheric
> pressure.
>
> Wikipedia tells me that the highest and lowest ever recorded
> barometric pressures are 108.57 kPa and 86.996 kPa,
> respectively.  It also tells me that "standard" atmospheric
> pressure is 101.325 kPa.  What it does NOT tell me (nor
> does anywhere else) is what the "normal" range is; that is,
> if a good, strong thunderstorm passes through, what can
> I expect the pressure to be?  Likewise, in a typical high
> pressure area, what can I expect the pressure to be?
>

http://www.noaa.gov/
If it's weather related, they've got it.

A quick poke around thier site and I found this:
www.ncdc.noaa.gov/oa/samples/lcdmonthly.pdf
looks like 1996 in Minnesota, I see a range of 28.7 to 30.6 (inches of mercury)

I'm sure a little digging will net some more information.

> I'm trying to develop a water depth gauge, and if possible,
> I'd like to get some feel for the variation of pressure based
> on atmospheric variations.  The highest to lowest cited
> above would represent a 2.2 meter(!) fluctuation in the
> depth of a body of water, if one were basing the depth on
> the pressure at the bottom.  Needless to say, that
> kind of variation would render the information useless.

Would depend on the application, two meters worst case might be good
enough for some apps.

Good Luck,
-Denny

2005\05\31@171326 by Herbert Graf

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face
On Tue, 2005-05-31 at 15:10 -0500, Mike Hord wrote:
> I'm trying to get a feel for the "normal" range of atmospheric
> pressure.
>
> Wikipedia tells me that the highest and lowest ever recorded
> barometric pressures are 108.57 kPa and 86.996 kPa,
> respectively.  It also tells me that "standard" atmospheric
> pressure is 101.325 kPa.  What it does NOT tell me (nor
> does anywhere else) is what the "normal" range is; that is,
> if a good, strong thunderstorm passes through, what can
> I expect the pressure to be?  Likewise, in a typical high
> pressure area, what can I expect the pressure to be?

Well, it's certainly going to depend on your area. Best idea would be to
consult your weather service. In Canada we have a web site where you can
get the history of certain weather details at your location going back a
few years.

Off hand, the highest I've seen my weather station is 104.5, the lowest
is about 96. Normal ranges are between 98 (raining) and 104 (very clear
sky, middle of winter).

Have you considered a "calibrate" button that is depressed at the
surface and zero adjusts to that pressure?

TTYL

---------------------------
Herbert's PIC Stuff:
http://repatch.dyndns.org:8383/pic_stuff/

2005\05\31@172153 by PicDude

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face
On Tuesday 31 May 2005 04:03 pm, Mike Hord scribbled:
> > > Differential measurement is NOT an option for this
> > > application.
> >
> > Bummer -- I was thinking of differential as I was reading this message.
>
> Yah, that'd make things MUCH easier.  However, the item in question
> must be self-contained and could be at reasonable depth.  It should
> also be as near to idiot-proof as possible, or at least VERY easy to use.


A land-based sensor could easily transmit to the submerged sensor.  Would keep
it self-contained to some extent.  Assuming a range of pressures seems like
it would add a significant error.

Cheers,
-Neil.


2005\05\31@172420 by Mike Hord

picon face
> >Differential measurement is NOT an option for this
> >application.
>
> Hmm.. Why not?
> Push some air down a line that goes to the bottom, and it will max
> out when you start bubbling.
> Pout - Pin and you're there I think.

The system in question (and I apologize for not being more specific
earlier) is a long-term in situ datalogger.  It would be unattended for
a minimum of a few days at a time, up to several weeks.  So the
solution needs to be very low power (which can be accomplished
by turning the sensor on and off as needed), small, and simple.

Differential would require a knowledge of the minimum and maximum
water levels, one "end" of the sensor could remain under water and
the other would be guaranteed to stay out of the water.  We've
considered a tube-and-float approach, or a post-with-tube method,
but they have their drawbacks (float snags on a passing log and
tears off; post must be placed, and tall, which detracts from the
convenience of the system).

It may be that it is impossible to do this without differential
measurement and still meet accuracy requirements.  In that case,
the best be may be an additional pressure only logger which sits
well above the high water line and monitors the ambient air
pressure.  That's good, too, because air pressure affects the
dissolved oxygen content of the water, which is another thing
we measure.

Mike H.

2005\05\31@182448 by Bob J

picon face
On 5/31/05, Mike Hord <spam_OUTmike.hordTakeThisOuTspamgmail.com> wrote:
> I'm trying to get a feel for the "normal" range of atmospheric
> pressure.

Mike, tonight when I get home I will look at the altimeter in my
airplane and see what the barometric pressure range is.  Speaking in
inches standard barometric setting is 29.92".  I've personally seen
barometric pressure greater than 31".  So once I can get you the range
in inches it would be trivial to convert the min/max to kPa.

Regards,
Bob


'[EE] Atmospheric Pressure Ranges'
2005\06\01@095839 by Peter
picon face

On Tue, 31 May 2005, Mike Hord wrote:

> I'm trying to get a feel for the "normal" range of atmospheric
> pressure.
>
> Wikipedia tells me that the highest and lowest ever recorded
> barometric pressures are 108.57 kPa and 86.996 kPa,
> respectively.  It also tells me that "standard" atmospheric
> pressure is 101.325 kPa.  What it does NOT tell me (nor
> does anywhere else) is what the "normal" range is; that is,
> if a good, strong thunderstorm passes through, what can
> I expect the pressure to be?  Likewise, in a typical high
> pressure area, what can I expect the pressure to be?

It depends at what altitude you are.

> I'm trying to develop a water depth gauge, and if possible,
> I'd like to get some feel for the variation of pressure based
> on atmospheric variations.  The highest to lowest cited
> above would represent a 2.2 meter(!) fluctuation in the
> depth of a body of water, if one were basing the depth on
> the pressure at the bottom.  Needless to say, that
> kind of variation would render the information useless.

Pressure based depth gauges use a differential transducer. One end is
exposed to the air. This removes the problem you describe and adds the
problem of having two tube openings to keep clean.

> Normal diurnal cycles are <.5 kPa, which corresponds
> to approximately 5 cm of water depth.  No info on
> typical changes outside those variations, however.
>
> Differential measurement is NOT an option for this
> application.

You can measure depth pretty accurately using ultrasound from below. The
water/air interface bounces it back strongly. But if you have waves it
will be hard anyway.

Peter

2005\06\01@102804 by Bill & Pookie

picon face
The gentleman who was going to look at his altimeter in his plane may have
the best information.  I assume that the instrument would be adjustable to
any pressure at any airport prior to starting a flight.  So the range of
adjustment would cover all "flying" weather.

Bill

{Original Message removed}

2005\06\01@110114 by Russell McMahon

face
flavicon
face
>> I'm trying to get a feel for the "normal" range of atmospheric
>> pressure.

Looking at a range of met weather forecast charts should do the trick.
On some at least the magnitude of highs and lows are shown. Met
experts or weather services can also probably answer this question
directly.


       RM

2005\06\01@121105 by Howard Winter

face
flavicon
picon face
Mike,

On Tue, 31 May 2005 15:10:50 -0500, Mike Hord wrote:

> Wikipedia tells me that the highest and lowest ever recorded
> barometric pressures are 108.57 kPa and 86.996 kPa,
> respectively.  It also tells me that "standard" atmospheric
> pressure is 101.325 kPa.  What it does NOT tell me (nor
> does anywhere else) is what the "normal" range is; that is,
> if a good, strong thunderstorm passes through, what can
> I expect the pressure to be?  Likewise, in a typical high
> pressure area, what can I expect the pressure to be?

The lowest I've ever encountered was 895mBar (=hPa)
the highest was 1045mBar (hPa)

The fastest change I've seen was in the late 1980s when there was a fast moving, really deep Low, and a drop
of around 5mBar/hr was sustained for over three hours.  It almost made your ears pop!  :-)

As a matter of (little) interest, it's currently 1015 mBar here, having fallen 4mBar over 9 hours, and it's
just started raining!

Cheers,


Howard Winter
St.Albans, England


2005\06\01@141522 by Bob J

picon face
Yes, aircraft altimeters are adjustable.  The dial that you set the
altimeter setting with is called the Kollsman window.  I got
sidetracked last evening, didn't make it over to the hangar, but have
to go there tonight.

Regards,
Bob

On 6/1/05, Bill & Pookie <.....reddxKILLspamspam@spam@comcast.net> wrote:
> The gentleman who was going to look at his altimeter in his plane may have
> the best information.  I assume that the instrument would be adjustable to
> any pressure at any airport prior to starting a flight.  So the range of
> adjustment would cover all "flying" weather.
>
> Bill
>
> {Original Message removed}

2005\06\01@150853 by Peter

picon face


On Wed, 1 Jun 2005, Bill & Pookie wrote:

> The gentleman who was going to look at his altimeter in his plane may have
> the best information.  I assume that the instrument would be adjustable to
> any pressure at any airport prior to starting a flight.  So the range of
> adjustment would cover all "flying" weather.

Yes but since the op wants something that can be left in place for a
while the airplane gentleman should also obtain the fastest recorded
barometer *change* observed over time. 50 mbar in 1 hour I have seen
myself (corresponds to about 0.5 meters of water column).

I still think ultrasound is valid and easily done for 2 meters of depth.
A collision detector circuit made for car parking could be adapted,
complete with sensor.

Peter

2005\06\01@173938 by Windman

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face
Google 'Standard Atmosphere'. You can then find the formula to compute
atmospheric pressure for any height.

HTH

Vic
___________________________________________________

Vic Fraenckel
KC2GUI
victorf AT windreader DOT com

"People sleep peacefully in their beds at night only because
rough men stand ready to do violence on their behalf."
                                                                George
Orwell


{Original Message removed}

2005\06\02@114054 by Geo

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On 31 May 2005, at 15:10, Mike Hord wrote:
>
> I'm trying to get a feel for the "normal" range of atmospheric
>> pressure.
Well - not at the airfield now - but Flight Sim 2002 altimeter is adjustable from
28.1 to 31.5 inches.


George Smith

2005\06\03@004458 by Bill Cornutt

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Was thinking more of the range of adjustment of the altimeter.

Bill

----- Original Message -----
From: "Peter" <plpspamKILLspamactcom.co.il>
To: "Microcontroller discussion list - Public." <.....piclistKILLspamspam.....mit.edu>
Sent: Wednesday, June 01, 2005 12:08 PM
Subject: Re: [EE] Atmospheric Pressure Ranges


>
>
> On Wed, 1 Jun 2005, Bill & Pookie wrote:
>
> > The gentleman who was going to look at his altimeter in his plane may
have
> > the best information.  I assume that the instrument would be adjustable
to
{Quote hidden}

> --

2005\06\03@104034 by Bob J

picon face
My altimeter adjusts from 28.1" to 31.0".

Regards,
Bob

On 6/2/05, Geo <EraseMElintechspam_OUTspamTakeThisOuTblueyonder.co.uk> wrote:
> On 31 May 2005, at 15:10, Mike Hord wrote:
> >
>  > I'm trying to get a feel for the "normal" range of atmospheric
> >> pressure.
>  Well - not at the airfield now - but Flight Sim 2002 altimeter is adjustable from
>  28.1 to 31.5 inches.
>
>
> George Smith
> -

2005\06\03@105637 by Mike Hord

picon face
> My altimeter adjusts from 28.1" to 31.0".
>
> Regards,
> Bob

Thanks for everyone's input.  It seems to me that some form
of differential measurement is necessary.

Ultrasound is interesting but may make deployment of the
instrument more complicated than people are willing to deal
with.  Standard MO right now is to tie a rope or cable to it,
toss it in the water and tie the other end to a large brick,
tree, or post on the riverside.  Anything requiring precise
orientation would likely turn people off.

Mike H.

2005\06\03@154032 by Robert Rolf

picon face
Mike Hord wrote:
> Thanks for everyone's input.  It seems to me that some form
> of differential measurement is necessary.
>
> Ultrasound is interesting but may make deployment of the
> instrument more complicated than people are willing to deal
> with.  Standard MO right now is to tie a rope or cable to it,
> toss it in the water and tie the other end to a large brick,
> tree, or post on the riverside.  Anything requiring precise
> orientation would likely turn people off.

What's so hard about getting correct orientation?
Rather than tying the long rope directly to the unit,
you attach it with a short extension length to the main rope.
That way the unit floats directly above the bend in the
rope, and with correctly shaped package, it always points
directly up (unless in strong current).
The fun part will be how well you can measure distance
to the surface.


   \SONAR/
    | G |
    | U |
    | T |
    | S |
    \Bat/
      O
      |
      |
      |
      +------To land line.
      |
      |
      T
      o
      |
      A
      n
      c
      h
      o
      r

Robert

2005\06\03@160447 by Mike Hord

picon face
{Quote hidden}

Not a bad idea.  May have to consider that.
Of course, it would mean making the device float, which
it currently does not (soundly).

Mike H.

2005\06\03@204315 by Hopkins

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face
Conversely have the ultrasonic head on an arm above the water and
measure the distance to the surface. Subtract that distance from the
ultrasonic head to the river bead to get the depth.

We us pressure transducer at work in sewer wells, they all have a
differential amplifier with air tube exposed to the air pressure, the
tube is built into the cable that powers the unit. The output is a
4-20ma current.  

_______________________________________

Roy
Tauranga
New Zealand
_______________________________________

-----Original Message-----

> What's so hard about getting correct orientation?


--
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2005\06\03@220415 by Robert Rolf

picon face
Mike Hord wrote:

>>What's so hard about getting correct orientation?
>>Rather than tying the long rope directly to the unit,
>>you attach it with a short extension length to the main rope.
>>That way the unit floats directly above the bend in the
>>rope, and with correctly shaped package, it always points
>>directly up (unless in strong current).
>>The fun part will be how well you can measure distance
>>to the surface.
>>
>>
    OO\SONAR/OO <-polyfoam float ring.
{Quote hidden}

Having it float would make it 'fail safe' if the rope breaks
or is cut. A lot easier to find it along a shore line, than
60' underwater. Just a matter of making the package displace
more water than the unit weighs. Might be as simple as
attaching a floatation collar.

R

2005\06\04@083956 by Bill & Pookie

picon face
I have a doggie life preserver you could use on it.  And how about a fishing
line attached to it with a bobber every fathom or so, to give you a rough
depth measurement by counting number of bobbers on surface.

Pookie

{Original Message removed}

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