Weather/units question for European members
Here in the US, most people who really care about wind speed think
knots. For causal use to the general public them it's MPH.
If you want to be esoteric use the "Beaufort Wind Scale" It is
actually still used because it can be estimated from looking at the
water. It is easy to learn to tell a 2, 3 ,4 just by looking
On Fri, May 23, 2014 at 9:21 PM, David J Taylor
david-taylor@blueyonder.co.uk wrote:
I am building a weather sensor that includes a ultrasonic anemometer to
measure wind speed, direction, and air temperature. It uses 4 cheap ($1
each) HC-SR04 ultrasonic rangefinder modules that output a pulse width
proportional to the time of flight of the sound signal (topic is time nut
related since it simultaneously measures the speed of sound in 4 directions
to a pretty good accuracy/resolution using a cheap-ass microprocessor -
ATMEGA328 (like and Arduino)... and does so without using any counter-timer
channels).
Now the question... I would like it to be able to output data in imperial
or metric units. In what units is the typical wind speed reported
(meters/sec, km/hour, ?). Also air pressure
(millibars/hectopascals/pascals/?).
---=============
Mark,
m/s and hPa are often used, but not exclusively.
Cheers,
David
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor@blueyonder.co.uk
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--
Chris Albertson
Redondo Beach, California
In message BLU170-W517A3E7D32E32BE4C3D3A4CE390@phx.gbl, Mark Sims writes:
I am building a weather sensor that includes a ultrasonic anemometer
Now the question... I would like it to be able to output data in
imperial or metric units. In what units is the typical wind speed
reported (meters/sec, km/hour, ?). Also air pressure
(millibars/hectopascals/pascals/?).
Whatever you do, use SI units internally and make it an option for the
user to get those. Convert from SI to whatever the user wants in their
local cultural geograpy.
PS: In Denmark we use the SI units: Meter per second and hectopascal.
See for instance:
http://www.dmi.dk/vejr/til-lands/regionaludsigten/vssjaelland/
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
Hi Mark,
I second Paul Henning,
here in Europe we use officially the SI standard, does mean m/s and hPa!
Privately used other units are another thing like km/h or units Beaufort
and mb (millibar),
but not official. If possible use always the international SI units and
as personal choice km/h,
hPa and millibar are anyway same numbers.
Regards
Arnold
Am 24.05.2014 03:16, schrieb Mark Sims:
I am building a weather sensor that includes a ultrasonic anemometer to measure wind speed, direction, and air temperature. It uses 4 cheap ($1 each) HC-SR04 ultrasonic rangefinder modules that output a pulse width proportional to the time of flight of the sound signal (topic is time nut related since it simultaneously measures the speed of sound in 4 directions to a pretty good accuracy/resolution using a cheap-ass microprocessor - ATMEGA328 (like and Arduino)... and does so wbbithout using any counter-timer channels).
Now the question... I would like it to be able to output data in imperial or metric units. In what units is the typical wind speed reported (meters/sec, km/hour, ?). Also air pressure (millibars/hectopascals/pascals/?).
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Hello,
Wind speed usually in meters/sec (when used for scientific data) or km/h
(used in the news, so the people can compare with car speed ;) )
Pressure in millibars. Meteorologist also usually refers to
hectopascals, but it is more for representing something at a given
altitude (for example, winds at 700hPa) than for managing pressure data.
Temperature in ºC
Precipitation in liters/squared meter or millimeters (it is a 1:1
equivalence)
Best regards,
Javier
On 24/05/2014 3:16, Mark Sims wrote:
I am building a weather sensor that includes a ultrasonic anemometer to measure wind speed, direction, and air temperature. It uses 4 cheap ($1 each) HC-SR04 ultrasonic rangefinder modules that output a pulse width proportional to the time of flight of the sound signal (topic is time nut related since it simultaneously measures the speed of sound in 4 directions to a pretty good accuracy/resolution using a cheap-ass microprocessor - ATMEGA328 (like and Arduino)... and does so without using any counter-timer channels).
Now the question... I would like it to be able to output data in imperial or metric units. In what units is the typical wind speed reported (meters/sec, km/hour, ?). Also air pressure (millibars/hectopascals/pascals/?).
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and follow the instructions there.
hektopascal is pseudo-SI form, as it is a compromize between the old
milibar and propper SI unit of Pascal with suitable prefix 1 mbar = 1
hPa, but since we have normal pressure at 1013 mbar we should write it
as 101,3 kPa but not 1013 hPa if we is to follow SI all the way.
Temperature in C is really not strict SI, but accepted.
m/s for windspeeds is the proper unit, while km/h is only used when
explaining high windspeeds.
Cheers,
Magnus
On 05/24/2014 02:01 PM, Javier Herrero wrote:
Hello,
Wind speed usually in meters/sec (when used for scientific data) or km/h
(used in the news, so the people can compare with car speed ;) )
Pressure in millibars. Meteorologist also usually refers to
hectopascals, but it is more for representing something at a given
altitude (for example, winds at 700hPa) than for managing pressure data.
Temperature in ºC
Precipitation in liters/squared meter or millimeters (it is a 1:1
equivalence)
Best regards,
Javier
On 24/05/2014 3:16, Mark Sims wrote:
I am building a weather sensor that includes a ultrasonic anemometer
to measure wind speed, direction, and air temperature. It uses 4
cheap ($1 each) HC-SR04 ultrasonic rangefinder modules that output a
pulse width proportional to the time of flight of the sound signal
(topic is time nut related since it simultaneously measures the speed
of sound in 4 directions to a pretty good accuracy/resolution using a
cheap-ass microprocessor - ATMEGA328 (like and Arduino)... and does
so without using any counter-timer channels).
Now the question... I would like it to be able to output data in
imperial or metric units. In what units is the typical wind speed
reported (meters/sec, km/hour, ?). Also air pressure
(millibars/hectopascals/pascals/?).
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To unsubscribe, go to
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and follow the instructions there.
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Hi Mark:
The key benefit of an ultrasonic wind speed/direction sensor is that it can detect very slow wind speeds.
My Peet Bros. system does not start telling me anything until the speed is a few MPH.
http://www.prc68.com/I/UltimeterWeatherStation.shtml
But all the weather stations I've seen don't tell you if the wind is backing or veering and how fast that's going on.
This is critical for forecasting.
It would be possible to have a graphical display the would be like looking down on a smoke stack with the smoke trail
showing the history of wind direction.
See the Sager Weather Caster book for more on that.
http://www.prc68.com/I/Weather.shtml
Have Fun,
Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
http://www.prc68.com/I/DietNutrition.html
Mark Sims wrote:
I am building a weather sensor that includes a ultrasonic anemometer to measure wind speed, direction, and air temperature. It uses 4 cheap ($1 each) HC-SR04 ultrasonic rangefinder modules that output a pulse width proportional to the time of flight of the sound signal (topic is time nut related since it simultaneously measures the speed of sound in 4 directions to a pretty good accuracy/resolution using a cheap-ass microprocessor - ATMEGA328 (like and Arduino)... and does so without using any counter-timer channels).
Now the question... I would like it to be able to output data in imperial or metric units. In what units is the typical wind speed reported (meters/sec, km/hour, ?). Also air pressure (millibars/hectopascals/pascals/?).
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