measurement of speed of wind , time of flight method

1. By:
Name: Pooja Dubey
Course: EEE
Roll No:120104026

2. Measurement of
speed of wind Anemometer
Hot wire anemometer
Wind mill anemometer
Laser doppler anemometer
Ultrasonic anemometer
Time of flight

3. Measurement of Wind Speed
Wind speed is the magnitude of the wind
velocity vector.
The wind velocity is a vector, which includes both
speed and direction.
Wind Speed is measured with a device called a
wind anemometer.
The term “anemometer” strictly refers to a general
fluid speed measuring device.
For example “hot wire anemometers” are used to
measure turbulence levels in fluid flows.
.

4.  An anemometer is a device to measure the wind
speed and direction. Wind measurement is
significant for detecting wind in industrial field.
Besides, wind measurement can be applied in
environment monitoring and controlling systems,
air conditioning systems and so on .

5. Hot wire anemometers use a very fine wire (mm) electrically
heated up to some temperature above the ambient.
Air flowing past the wire has a cooling effect on the wire.
Hot Wire Anemometer allows accurate monitoring for very low air
velocity measurements.

6. 1) Hot Wire / Film Anemometer

7.  The other form of mechanical velocity
anemometer is windmill type or propeller
anemometer.
 An aerovane combines a propeller and a tail
on the same axis to obtain accurate and
precise wind speed and direction
measurements from the same instrument.
 where the direction of the air motion is always
the same, as in the ventilating shafts of mines
and buildings,air meters are employed, which

8. Some pictures showing
usage of
WINDMILL
ANEMOMETER

9.  The Laser Doppler Anemometer is a very high-tech
anemometer, so it is usually more accurate.
 Laser Doppler anemometers use a beam of light from a
laser that is divided into two beams, with one propagated
out of the anemometer. The air particles caught in the
beam are reflected back into the anemometer
where it’s measured.
 When the particles are in great motion, they produce a
Doppler shift for measuring wind speed in the laser light,
which is used to calculate the speed of the particles, and
therefore the air around the anemometer.

10. Some pictures showing
usage of
LASER
DOPPLER
ANEMOMETER

11.  The anemometers described above use the wind kinetic energy to
support the measurement. They do not need any extra source to
provide parameters.
 There are some other types of anemometer which introduce extra
sources as parameters to wind speed, for example the speed of
sound.
 One of such anemometer is ultrasonic anemometer.

12.  It uses ultrasonic propagation time as the
parameter to wind speed. The ultrasonic is
generated from an ultrasonic source and
received by an ultrasonic receiver.
 The propagation time is really short. By
measuring the propagation time, the wind speed
can be determine.
 . In order to do this, there are some objectives
which need to achieve
 1. Construct the test bed which consists of
ultrasonic transmitter and receiver.
 2. Measure the different wind velocity.
.

13. FIG 1. TEST BED

14.  Dash rectangle box is the test bed where the
measurement is done, the dotted line is the propagation
distance over which time is measured.
 The generator provides power to the ultrasonic source
which transmits ultrasound
 Digital oscilloscope is used to measure the time
difference between transmit and receive which is the
propagation time. Filter is used to eliminate the
frequency which is not equal to the transmitted signal.
 The reason to choose the ultrasound instead of audio
sound is that ultrasonic has much higher frequency than
audio sound.

16.  In the last slide, there is a setup showing the
wave speed in two cases.
 The role of the transmitter and receiver can be
changed.
 In the first case, path 1 to 2,1 is the left point and
2 is the right point, the wave travels at a speed of
c minus V.
 Therefore time of flight is distance traveled

17.  In the second case, path 2 to 1,1 is the left point
and 2 is the right point, the wave travels at a
speed of c plus V.
 Therefore time of flight is distance traveled
divided by the velocity, L by c plus V for the
backward path.

21.  Ultrasonic anemometers require less
maintenance, respond better to rapid wind gusts.
 Accuracy is high.
 New high-tech ultrasonic instruments used to
measure wind speed and direction and are
reliable .
 Well suited for turbulence measurements.

23.  This study produced a basic one-dimensional
ultrasonic anemometer using the theory of
Time of flight (TOF).The transducers used in
this experiment are cheap and simple
functional. Sonic anemometers can take
measurements with very fine temporal
resolution, 20 Hz or better, which makes
them well suited even
for turbulence measurements

24.  D. Han, S. Kim and S. Park, “One-dimensional
ultrasonic anemometer using the directivity angle of
an ultrasonic sensor, volume 39 , October 2008.
 D. Han and S. Park, “A Study on Characteristics of
Continuous Wave Ultrasonic Anemometer,”
Sensors Applications Symposium ,February 2011.
 M.P. del Valle, J.A.U. Castelan, Y. Matsumoto and
R.C. Mateos, “Low Cost Ultrasonic Anemometer,”
Electrical and Electronics Engineering, 2007.
 http://www.slideshare.net/snesajid/anemometer-
14285929