Calling Weather Experts: What do you Need in a Barograph?

[nigelmercier]

Some time ago I ordered some barometric pressure sensors with the aim of building a barograph. Then I saw the MeteoMan from Nasa on sale, so I gave in and bought one. However, while it has a good range of display options, it is lacking in several areas:

[1] There is no alarm! Really? No "Danger Will Robinson!" when the pressure drops rapidly.
[2] It doesn't give absolute pressure; it has an option to change the displayed pressure to compensate for altitude. Altitude? Again, really?
[3] When you switch between the graphical displays, the time axis does not coincide (see pictures).
[4] It uses mb. OK, so I'm being purist.

So I'm back to the idea of making a compact device which will show:
[1] Current absolute pressure with barograph display
[2] Current pressure with trend display and alarm

This is what the corresponding MeteoMan displays look like (actual 27 March 12:00):

Questions:

[1] Current pressure with barograph display
How far back in time do you really need to store/display?
12h? 24h? Or up to 80h (!) like the MeteoMan?
What pressure range do you need?
MeteoMan has 980-1030 and 950-1050.

[2] Current pressure with trend display and alarm
How far back in time do you really need to store/display?
Is the one-hour averaged rate optimal?
Does this display give you all you need?
At what rate of falling pressure would you set an alarm? 1mb/hour, 3mb/3h ... ?
Need for two alarms at two levels?
Would a colour display be useful? More expensive, but could have red as alarm indicator.

 

[Joker]

I've been looking for an electronic barograph for some time.

I wouldn't be bothered about hPa vs mb: it's the trend one is usually interested in. A bar display is obviously the most useful, and 24 hours maximum.

The idea of a 'rate of change' display is a nice one.

 

[KellysEye]

We used a barometer and made a note of the pressure in the log we updated every two hours.

 

[GHA]

I've been looking for an electronic barograph for some time.

I wouldn't be bothered about hPa vs mb: it's the trend one is usually interested in. A bar display is obviously the most useful, and 24 hours maximum.

The idea of a 'rate of change' display is a nice one.

Fo rwell over a decade i've never felt a need for any more than one of these. Does what's required. If you need an alarm for pressure drop then you aren't paying enough attention to both the gribs & the barometer

 

[sailaboutvic]

I tend to check the presser every morning , this morning , 140 / 90 Must cut down on the drinking

 

[VicS]

You need a good quality barometer mechanism and a good clock movement.

A good mahogany case with bevelled glass and a chart drawer

A diall in addition to the chart recorder is an attractive feature

 

[RichardS]

Fo rwell over a decade i've never felt a need for any more than one of these. Does what's required. If you need an alarm for pressure drop then you aren't paying enough attention to both the gribs & the barometer

I've got one of those 'cept it's got an external sensor as well as the internal which connects by wifi or bluetooth or something.

Means I get twice as many numbers! :encouragement:

Richard

 

[{151760}]

It is necessary to compensate for altitude with any barometer, as the higher you are the lower the pressure. Pilots customarily set their analogue altimeters (which work exactly as barometers do) to the altitude of the airfield they depart from. There is no 'absolute' air pressure; the Met Office gives air pressure at sea level, I believe.

 

[RobbieW]

It is necessary to compensate for altitude with any barometer, as the higher you are the lower the pressure. Pilots customarily set their analogue altimeters (which work exactly as barometers do) to the altitude of the airfield they depart from. There is no 'absolute' air pressure; the Met Office gives air pressure at sea level, I believe.

Umm, above a certain flight level do pilots not use 1013.25 since if they all used the QFE number they'd be in danger of collision ? (though its 45 years since I was taught this stuff). I go along with those who go for a trend over max 24 hrs as thats whats useful to a yottie.

 

[{151760}]

Umm, above a certain flight level do pilots not use 1013.25 since if they all used the QFE number they'd be in danger of collision ? (though its 45 years since I was taught this stuff). I go along with those who go for a trend over max 24 hrs as thats whats useful to a yottie.

Possibly, but nonetheless, it's necessary to calibrate a barometer for height.

 

[prv]

It is necessary to compensate for altitude with any barometer, as the higher you are the lower the pressure.

So how high are Nasa expecting their customers' yachts to fly?

Pete

 

[Newboy6458]

Most private pilots use height above airfield or QFE for flying circuits and take off and landing. Flying between airports a regional pressure setting or QNH is used. This is the lowest forecast setting for that area for the next hour and is based on a mean sea level setting and therefore roughly corresponds to altitude. Commercial air traffic tends to use actual QNH settings for the airport they are using. 1013 is set for flight on airways. The transition altitude varies according to terrain and country.

To correct your barometer at home for elevation, 1mb is worth 30 feet in old money.

Hope this helps

 

[Gwylan]

Have a NASA Meteoman - linked to a knackered wind jobbie.

The trend is the most important, probably rapid falls more worrying than rises.

The height compensation is a bit unnecessary
60 hour memory and some kind of 12 hour forward trend
not silly suns, clouds or rainy cloud symbols
Do not need an alarm, just a heads up that the trend is serious
rising or falling; slowly, quickly, very rapidly - could be + or - the more means the bigger problem, or opportunity
In a display that will fit the hole occupied by the Meteoman or a NASA Clipper unit.

 

[Sybarite]

Paper?

 

[Joker]

Possibly, but nonetheless, it's necessary to calibrate a barometer for height.

I don't find that a problem in a yacht. Do you know something I don't?

 

[KellysEye]

>Pilots customarily set their analogue altimeters (which work exactly as barometers do) to the altitude of the airfield they depart from. There is no 'absolute' air pressure; the Met Office gives air pressure at sea level, I believe.

I put my skydiving altimeter on our kitchen unit and set it to zero, over the last year the unit has been 1,000 feet high and 200 feet below ground as the pressure changes.

 

[RichardS]

So how high are Nasa expecting their customers' yachts to fly?

Pete

I have a second yacht on Lake Titicaca ....... 11,000 feet!

Richard

 

[Fossil]

If looking for a cheap, effective barograph, forget the elegant heavyweight steam-punk designs with mahogany and glass cases and clockwork mechanisms: have a look in the hang-gliding and paragliding magazines. These boys have to substantiate their long flights (and 150km in the UK is becoming by no means unusual) with a barograph trace, if they want to claim a record, or have their flight entered in the ongoing distance competition.

Hence that market offers several superb electronic versions, relatively cheap, which will interface with personal computers or mobile phone apps to give a trace at intervals as short - or as long - as you want.

 

[jakeroyd]

A slight aside but have you tried a smartphone app.
This one (Android) can have a strom alarm set.
https://play.google.com/store/apps/details?id=jos.verbeek.barograph

 

[jakeroyd]

Correction.
Works on phones with of course a barometric sensor.
Motorola Xoom, Galaxy Nexus, Galaxy Note or the Sony Xperia Active etc.