airspeed measurement
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I am trying to measure airspeed on a radio controlled airplane. I think I
need to connect a differential pressure transducer to an A/D to a BS2. The
differential pressure transducer will measure the difference between
oncoming air pressure vs. local air pressure.
3 questions:
1. Has anyone tried this and have any tips or suggestions?
2. What range 0 to ? psi transducer would I need given that I want to
measure speeds up to 60 mph?
3. Any suggestions on where to find small, light weight, inexpensive
differential transducers.
Thanks for any help.
- Alex
need to connect a differential pressure transducer to an A/D to a BS2. The
differential pressure transducer will measure the difference between
oncoming air pressure vs. local air pressure.
3 questions:
1. Has anyone tried this and have any tips or suggestions?
2. What range 0 to ? psi transducer would I need given that I want to
measure speeds up to 60 mph?
3. Any suggestions on where to find small, light weight, inexpensive
differential transducers.
Thanks for any help.
- Alex
Comments
is a Motorola MPX5500DP.
I'd have to set down and calculate what the stagnation pressure would be at
60 to 100 mph to determine what range you should use.
Let me know how it works out.
You can get data sheets and app notes at the Motorola site.
Original Message
From: Alex Sulkowski <asulkowski@a...>
To: <basicstamps@yahoogroups.com>
Sent: Tuesday, November 06, 2001 9:54 AM
Subject: [noparse][[/noparse]basicstamps] airspeed measurement
> I am trying to measure airspeed on a radio controlled airplane. I think I
> need to connect a differential pressure transducer to an A/D to a BS2.
The
> differential pressure transducer will measure the difference between
> oncoming air pressure vs. local air pressure.
> 3 questions:
> 1. Has anyone tried this and have any tips or suggestions?
> 2. What range 0 to ? psi transducer would I need given that I want to
> measure speeds up to 60 mph?
> 3. Any suggestions on where to find small, light weight, inexpensive
> differential transducers.
> Thanks for any help.
> - Alex
>
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the simple calculation is to take a Pitot tube,
and put the high and low pressues into a differential
pressure transmitter.
the square root of the differential pressure times
4005 will yield feet per minute.
This is cheap and dirty as it does not allow
for air density (temperature and pressure)
but assumes you are at 50% humidity
at 29.92 inches of mercury barometric pressure
and at 69 deg F.
Anyone who flys knows air density and temperatre
are major factors in air speed calculations.
If you want a more detailed formula, let me know.
btw, NASA uses a Pitot tube on the Space Shuttle
so you are on the right track.
you may want to look for a pressure sensor that measures
in inches of water, not PSI. ONE inch of water
differential pressure is equal to 4005 Feet per minute
as above, TWO inches is about 5,664 FPM or slightly over
60 miles per hour. SEVEN inches is close to 100 MPH.
There are 27.72 inches of water in one PSI, so your
60 to 100 miles per hour will be in the
less than one PSI range.
For simplicity I rounded everything to integers
so don't use this as gospel.
Dave
--- In basicstamps@y..., Alex Sulkowski <asulkowski@a...> wrote:
> I am trying to measure airspeed on a radio controlled airplane. I
think I
> need to connect a differential pressure transducer to an A/D to a
BS2. The
> differential pressure transducer will measure the difference between
> oncoming air pressure vs. local air pressure.
> 3 questions:
> 1. Has anyone tried this and have any tips or suggestions?
> 2. What range 0 to ? psi transducer would I need given that I
want to
> measure speeds up to 60 mph?
> 3. Any suggestions on where to find small, light weight,
inexpensive
> differential transducers.
> Thanks for any help.
> - Alex
and a tube running from the leading edge of one of the wings down
to blow on the vane. The faster the air moves, the faster the vane
rotates, the more voltage the motor (generator mode) produces.
Record readings by holding the sensor out the window of your car
(with caution) and reading the speedo to see if it gives you the
range and accuracy you need.
This motor would need to be one that would run on less than 6
volts and very low torque. The lower the torque, the weaker the
magnets, the less force required to make it turn. . .you get the
idea. . .
P.S. This is one method used in planes to record airspeed.
On 6 Nov 2001, at 9:54, Alex Sulkowski wrote:
> I am trying to measure airspeed on a radio controlled airplane. I
> think I need to connect a differential pressure transducer to an A/D
> to a BS2. The differential pressure transducer will measure the
> difference between oncoming air pressure vs. local air pressure. 3
> questions: 1. Has anyone tried this and have any tips or suggestions?
> 2. What range 0 to ? psi transducer would I need given that I want to
> measure speeds up to 60 mph? 3. Any suggestions on where to find
> small, light weight, inexpensive differential transducers. Thanks for
> any help. - Alex
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
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> and Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
>
>
I was thinking about the air speed measuring and
thought about a couple other solutions.
I really like the motor acting as a generator idea
and a rotometer is what is used in the petrolium inductry
to measure Custody Transfer, as they are (or can be) so
accuate.
Vortex Shedding is another method, and one that offers
itself to air speed. In Star Trek Voyager, in the opening
credits Voyager flies through a stellar cloud and
leaves a 'wake' that has alternate swirls. That is the
effect caused by air or gas or liguid passing a bluff body.
the air has a high pressure on one side and low on the other
and there is a push form high to low. this then changes
and the low side gets a higher pressure and the high goes
low. Anyway, the resulting back and forth pulsations
can be measured by a piezio as alternating
high/low pressure. The rate of pulses are linear to
speed, so all you are left with is to calibrate for
air density.
I am not sure of the rate of pulses, but I would assume
that they would be too fast to monitor directly with
a stamp.
This is one of the ways used by auto manufacturers
to measure air flow into the engine. That means
that a rough sensor unit may be had at a used auto
parts supply.
Dave
--- In basicstamps@y..., Alex Sulkowski <asulkowski@a...> wrote:
> I am trying to measure airspeed on a radio controlled airplane. I
think I
> need to connect a differential pressure transducer to an A/D to a
BS2. The
> differential pressure transducer will measure the difference between
> oncoming air pressure vs. local air pressure.
> 3 questions:
> 1. Has anyone tried this and have any tips or suggestions?
> 2. What range 0 to ? psi transducer would I need given that I
want to
> measure speeds up to 60 mph?
> 3. Any suggestions on where to find small, light weight,
inexpensive
> differential transducers.
> Thanks for any help.
> - Alex
Dave, I think I'm going to stick with the pressure sensor because the piezo
method you described is a little beyond my abilities.
Thanks again to all.
- Alex
As some other folks on this list I'm building a speedometer for RC
aircrafts. After my hardware is roughly finished I started to
investigate calibration and accurracy. I'm using a pitot tube and a
MPX2010 pressure sensor, with a LTC1298 AD.
I found out that air density varies approx from 1.15 to 1.3 kg/m3,
for temperatures between 0 to 40C in dry air.
Does anyone know how barometric pressure and humidity affects air
density, although my engineeering library is extensive I can't seen
to find any figures on that.
If anyone else is working on similar projects, it would be fun to
hear your ideas or opinions.
/Douglas
Try to find documentation and explanations over the
MOLLIER diagram. It is a matter too extensive to explain by mail in my
elementary english.
Regards
ECO
Original Message
From: "goggaz1" <rdo@s...>
To: <basicstamps@yahoogroups.com>
Sent: Tuesday, January 01, 2002 3:08 PM
Subject: [noparse][[/noparse]basicstamps] Airspeed measurement
>
> Hi!
>
> As some other folks on this list I'm building a speedometer for RC
> aircrafts. After my hardware is roughly finished I started to
> investigate calibration and accurracy. I'm using a pitot tube and a
> MPX2010 pressure sensor, with a LTC1298 AD.
> I found out that air density varies approx from 1.15 to 1.3 kg/m3,
> for temperatures between 0 to 40C in dry air.
>
> Does anyone know how barometric pressure and humidity affects air
> density, although my engineeering library is extensive I can't seen
> to find any figures on that.
>
> If anyone else is working on similar projects, it would be fun to
> hear your ideas or opinions.
>
>
> /Douglas
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and Body
of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>
Fascinating project.
Maybe it would be helpful to use a pair of sensors: one for the pitot and one
for a static reading, as in the full
scale instrument. I think the idea is to take a differential reading between
the sensor on the static line and the
sensor on the pitot line, so that most variables other than airspeed (e.g.
altitude effects) cancel out.
Will you transmit the data back to earth? Or is this for a flight recorder type
data logger?
Best, Michael
ECO wrote:
> Douglas
> Try to find documentation and explanations over the
> MOLLIER diagram. It is a matter too extensive to explain by mail in my
elementary english.
> Regards
> ECO
>
Original Message
> From: "goggaz1" <rdo@s...>
> To: <basicstamps@yahoogroups.com>
> Sent: Tuesday, January 01, 2002 3:08 PM
> Subject: [noparse][[/noparse]basicstamps] Airspeed measurement
>
> >
> > Hi!
> >
> > As some other folks on this list I'm building a speedometer for RC
> > aircrafts. After my hardware is roughly finished I started to
> > investigate calibration and accurracy. I'm using a pitot tube and a
> > MPX2010 pressure sensor, with a LTC1298 AD.
> > I found out that air density varies approx from 1.15 to 1.3 kg/m3,
> > for temperatures between 0 to 40C in dry air.
> >
> > Does anyone know how barometric pressure and humidity affects air
> > density, although my engineeering library is extensive I can't seen
> > to find any figures on that.
> >
> > If anyone else is working on similar projects, it would be fun to
> > hear your ideas or opinions.
> >
> >
> > /Douglas
> >
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@yahoogroups.com
> > from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
> >
> >
> > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
> >
> >
> >
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and Body
of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
ECO:
My MOLLIER diagrams (a have a few) only shows for properties at sea
level, I guess air is lighter the higher you get, but how much?
My search goes on, NASA has a good but very big website....[noparse]:)[/noparse])
Michael:
Could you cancel out the barometric effects?
The setup with two sensors have crossed my mind, one for barometric
pressure (height above sea level) and one for airspeed. However, I'm
limited by size and weight, we'll se what comes out of it...
Transmitting it to earth is in the plans, it removes any code, weight
and space for the eeprom. BUT: any RC pilot is very scared of radio
interference, any it would be a very effective way to be sure to
always fly alone [noparse]:)[/noparse]...
I will definately try anyway!
Sincerelly!
/Douglas
--- In basicstamps@y..., Michael Gianturco <michcg@m...> wrote:
> Hello Douglas,
>
> Fascinating project.
>
> Maybe it would be helpful to use a pair of sensors: one for the
pitot and one for a static reading, as in the full
> scale instrument. I think the idea is to take a differential
reading between the sensor on the static line and the
> sensor on the pitot line, so that most variables other than
airspeed (e.g. altitude effects) cancel out.
>
> Will you transmit the data back to earth? Or is this for a flight
recorder type data logger?
>
> Best, Michael
>
>
>
>
> ECO wrote:
>
> > Douglas
> > Try to find documentation and explanations over the
> > MOLLIER diagram. It is a matter too extensive to explain by mail
in my elementary english.
> > Regards
> > ECO
> >
Original Message
> > From: "goggaz1" <rdo@s...>
> > To: <basicstamps@y...>
> > Sent: Tuesday, January 01, 2002 3:08 PM
> > Subject: [noparse][[/noparse]basicstamps] Airspeed measurement
> >
> > >
> > > Hi!
> > >
> > > As some other folks on this list I'm building a speedometer for
RC
> > > aircrafts. After my hardware is roughly finished I started to
> > > investigate calibration and accurracy. I'm using a pitot tube
and a
> > > MPX2010 pressure sensor, with a LTC1298 AD.
> > > I found out that air density varies approx from 1.15 to 1.3
kg/m3,
> > > for temperatures between 0 to 40C in dry air.
> > >
> > > Does anyone know how barometric pressure and humidity affects
air
> > > density, although my engineeering library is extensive I can't
seen
> > > to find any figures on that.
> > >
> > > If anyone else is working on similar projects, it would be fun
to
> > > hear your ideas or opinions.
> > >
> > >
> > > /Douglas
> > >
> > >
> > > To UNSUBSCRIBE, just send mail to:
> > > basicstamps-unsubscribe@y...
> > > from the same email address that you subscribed. Text in the
Subject and Body of the message will be ignored.
> > >
> > >
> > > Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/
> > >
> > >
> > >
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@y...
> > from the same email address that you subscribed. Text in the
Subject and Body of the message will be ignored.
> >
> >
> > Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/
If you live near a small airport go there as see if you can get airspeed
calibration calculators. These are like a circular slide rule - you set in
temp, pressure and altitude and the calculator does the work for you.
Sid
I would suggest that you determine the indicated air speed for your
application.I will try to enclose 4 data sheets which I think will be
helpful.In effect you will measure the ambient static pressure and
the pressure impacting the pitot tube and from a lookup table
determine the indicated speed of the aircraft.The artcle address the
problem of determing the air speed of a small plane and should be
helpful I don't think that I can insert the pages I want to send
you.My email address is durango2@j... contact me and I will
email the 4 pages.--- In basicstamps@y..., "goggaz1" <rdo@s...> wrote:
> Hi!
>
> As some other folks on this list I'm building a speedometer for RC
> aircrafts. After my hardware is roughly finished I started to
> investigate calibration and accurracy. I'm using a pitot tube and a
> MPX2010 pressure sensor, with a LTC1298 AD.
> I found out that air density varies approx from 1.15 to 1.3 kg/m3,
> for temperatures between 0 to 40C in dry air.
>
> Does anyone know how barometric pressure and humidity affects air
> density, although my engineeering library is extensive I can't seen
> to find any figures on that.
>
> If anyone else is working on similar projects, it would be fun to
> hear your ideas or opinions.
>
>
> /Douglas