Meteorology -- Sonic anemometers/thermometers -- Acceptance test methods for mean wind measurements

ISO 16622:2002 defines test methods of the performance of sonic anemometers/thermometers which employ the inverse time measurement for velocity of sound along differently oriented paths. It is applicable to designs measuring two or three components of the wind vector within an unlimited (360°) azimuthal acceptance angle.

Météorologie -- Anémomètres/thermomètres soniques -- Méthodes d'essai d'acceptation pour les mesurages de la vitesse moyenne du vent

L'ISO 16622:2002 définit des méthodes d'essai permettant d'évaluer la performance des anémomètres/thermomètres soniques qui mesurent la vitesse du son le long de trajets à orientations diverses, en raison inverse du temps. Elle est applicable aux instruments mesurant deux ou trois composantes du vecteur vent dans un angle d'acceptation azimutal illimité (360°).

Meteorologija – Zvočni anemometri/termometri – Preskus sprejemljivosti metode za določanje povprečne vrednosti vetra

General Information

Status
Published
Publication Date
25-Sep-2002
Technical Committee
Current Stage
6060 - International Standard published
Start Date
10-Jul-2002
Completion Date
26-Sep-2002

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INTERNATIONAL ISO
STANDARD 16622
First edition
2002-09-15
Meteorology — Sonic
anemometers/thermometers — Acceptance
test methods for mean wind measurements
Météorolgie — Anémomètres/thermomètres soniques — Méthodes d'essai
d'acceptation pour les mesurages de la vitesse moyenne du vent
Reference number
ISO 16622:2002(E)
ISO 2002
---------------------- Page: 1 ----------------------
ISO 16622:2002(E)
PDF disclaimer

This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but shall not

be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this

file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat accepts no liability in this

area.
Adobe is a trademark of Adobe Systems Incorporated.

Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters

were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event

that a problem relating to it is found, please inform the Central Secretariat at the address given below.

© ISO 2002

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic

or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO's member body

in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.ch
Web www.iso.ch
Printed in Switzerland
ii © ISO 2002 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 16622:2002(E)
Contents Page

Foreword .................................................................................................................................................................... iv

Introduction................................................................................................................................................................. v

1 Scope.............................................................................................................................................................. 1

2 Normative references.................................................................................................................................... 1

3 Terms and definitions................................................................................................................................... 1

4 Symbols and abbreviated terms.................................................................................................................. 3

5 Summary of methods.................................................................................................................................... 4

6 Array examination prior to testing .............................................................................................................. 5

7 Zero wind chamber test................................................................................................................................ 5

7.1 Purpose .......................................................................................................................................................... 5

7.2 Procedure....................................................................................................................................................... 5

8 Wind tunnel test ............................................................................................................................................ 6

8.1 Purpose .......................................................................................................................................................... 6

8.2 Precaution...................................................................................................................................................... 6

8.3 Wind tunnel test procedure.......................................................................................................................... 7

9 Pressure chamber test (optional) ................................................................................................................ 9

9.1 Purpose .......................................................................................................................................................... 9

9.2 Apparatus..................................................................................................................................................... 10

9.3 Procedure..................................................................................................................................................... 10

10 Field tests..................................................................................................................................................... 10

10.1 Purpose ........................................................................................................................................................ 10

10.2 Duration........................................................................................................................................................ 10

10.3 Siting............................................................................................................................................................. 10

10.4 Field site equipment.................................................................................................................................... 11

10.5 Evaluation .................................................................................................................................................... 11

Annex A (informative) Zero wind chamber.............................................................................................................13

Annex B (informative) Wind measurement with sonics........................................................................................ 14

Annex C (normative) Wind tunnel........................................................................................................................... 18

Annex D (informative) Acoustic impedance versus altitude................................................................................ 20

Bibliography.............................................................................................................................................................. 21

© ISO 2002 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 16622:2002(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO

member bodies). The work of preparing International Standards is normally carried out through ISO technical

committees. Each member body interested in a subject for which a technical committee has been established has

the right to be represented on that committee. International organizations, governmental and non-governmental, in

liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical

Commission (IEC) on all matters of electrotechnical standardization.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.

The main task of technical committees is to prepare International Standards. Draft International Standards adopted

by the technical committees are circulated to the member bodies for voting. Publication as an International

Standard requires approval by at least 75 % of the member bodies casting a vote.

Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights.

ISO 16622 was prepared by Technical Committee ISO/TC 146, Air quality, Subcommittee SC 5, Meteorology.

Annex C forms a normative part of this International Standard. Annexes A, B and D are for information only.

iv © ISO 2002 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 16622:2002(E)
Introduction

Most human activity influencing the dispersion of anthropogenic pollutants occurs within the surface layer (SL), that

portion of the atmosphere which lies within a few tens of metres of the earth's surface. The SL is typified by sharp

gradients and time-varying fluxes of heat, moisture and momentum. Three-dimensional flow and turbulence

information resolved over short temporal and spatial scales is needed to characterize the SL. This information must

be presented not only as time-mean quantities, but also as the turbulent fluctuations of those quantities which

contribute to the production, transport, dispersion and dissipation processes operating within the SL. The sonic

anemometer/thermometer (shortened to “sonic” in the following) is an instrument well suited to obtain

measurements necessary for SL characterization.

A sonic consists of a transducer array containing paired sets of ultrasonic transmitter/receivers, and circuitry

designed to measure the transit times of acoustic waves propagating over the path (typically 10 cm – 20 cm)

between transducer pairs. A three-dimensional array resolves horizontal and vertical wind components plus the

speed of sound from which the sonic (virtual) temperature can be derived. Sonic anemometry has been used for

several decades in atmospheric research, but recent advances in instrument design and signal processing,

coupled with increased sophistication of atmospheric dispersion models, has led to an increasing demand for their

use, including routine wind speed and direction measurements. Because they contain no moving parts, sonics offer

low maintenance and operational advantages in adverse weather conditions. These factors have stimulated the

commercial manufacture of sonics and the drafting of several national sonic standards which form the basis for the

following International Standard of performance measurements and test methods.

The procedures presented in this document define methods for acceptance testing of sonics to be used for mean

wind measurements. Minimum requirements for conformance with this International Standard include successful

completion of the zero wind chamber test (clause 7), the wind tunnel test (clause 8), and the field test (clause 10).

The pressure chamber test (clause 9) is recommended if the sonic is to be used at elevations higher than 2 000 m

above mean sea level.
© ISO 2002 – All rights reserved v
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 16622:2002(E)
Meteorology — Sonic anemometers/thermometers — Acceptance
test methods for mean wind measurements
1 Scope

This International Standard defines test methods of the performance of sonic anemometers/thermometers which

employ the inverse time measurement for velocity of sound along differently oriented paths. It is applicable to

designs measuring two or three components of the wind vector within an unlimited (360°) azimuthal acceptance

angle.
2 Normative references

The following normative documents contain provisions which, through reference in this text, constitute provisions of

this International Standard. For dated references, subsequent amendments to, or revisions of, any of these

publications do not apply. However, parties to agreements based on this International Standard are encouraged to

investigate the possibility of applying the most recent editions of the normative documents indicated below. For

undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC

maintain registers of currently valid International Standards.

ISO 5725-1, Accuracy (trueness and precision) of measurement methods and results — Part 1: General principles

and definitions

ISO 5725-2, Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic method for

the determination of repeatability and reproducibility of a standard measurement method

ASTM D5741-96, Standard Practice for Characterizing Surface Wind Using a Wind Vane and Rotating

Anemometer

WMO CIMO, 1996 World Meteorological Organization (ed.) Guide to meteorological instruments and methods of

observation. WMO-No.8, 6th edn. 1996, Geneva
3 Terms and definitions

For the purposes of this International Standard, the following terms and definitions apply.

3.1
array

mechanical structure to support the sonic transducers in the desired geometric configuration

3.2
array symmetry angle
angular distance about which the array is symmetrical
3.3
mean
mean value over the (selected) averaging interval of the sonic
© ISO 2002 – All rights reserved 1
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ISO 16622:2002(E)
3.4
sonic
sonic anemometer/thermometer

instrument consisting of a transducer array containing sets of acoustic transmitters and receivers, a system clock,

and microprocessor circuitry to measure intervals of time between the transmission and reception of sound pulses

3.5
sound path
path between a pair of transducers
3.6
system delay

difference between the electronically detected total propagation time and the transit time

NOTE The time between the electronic generation of the transmission signal and the electronic detection of the received

signal is longer than the transit time due to the propagation times through the transducers and the electronic circuitry.

3.7
transit time
time required by a sound wave front to propagate between a pair of transducers
3.8
turbulence level
turbulence intensity
ratio of the square root of the turbulent kinetic energy to the mean wind speed
22 2
′′ ′
uv++w
T = (1)
where
′ denotes deviations from the mean.
EXAMPLE uu=−u , etc., where
u is the instantaneous wind component
u is the mean wind component.
3.9
zero offset
wind speed indicated by the sonic in calm air
2 © ISO 2002 – All rights reserved
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ISO 16622:2002(E)
4 Symbols and abbreviated terms
T temperature, in kelvin
T sonic temperature, in kelvin [see equation (B.4)]
T turbulence intensity

U speed of the undisturbed flow in the wind tunnel, speed, or wind speed measured by a reference

sensor, in metres per second
U wind speed, sonic output, in metres per second with sonic azimuth a
U wind speed, sonic output, in metres per second with sonic azimuth b
U nth sample of U , in metres per second
a,n a
U vectorial average of U , in metres per second
v a
U scalar average of U , in metres per second
s a
U specified maximum speed measurable with the sonic, in metres per second
max
U minimum test speed, in metres per second
min
−2 −1
Z acoustic impedance (Z = ρ⋅c [kg⋅m ⋅s ])
a sonic azimuth, in degrees
b sonic azimuth, in degrees
c speed of sound, in metres per second
d path length, in metres
e water vapour partial pressure, in hectopascals
h height above mean sea level, in metres
p pressure, in hectopascals
p equivalent pressure, in hectopascals (see Table D.1)
t averaging interval, in seconds
t transit time from transducer+ to transducer− , in seconds
t transit time from transducer− to transducer+ , in seconds

u ,v ,w along-axis, cross-axis, and vertical velocity components of the undisturbed flow, in metres per second

0 0 0

u ,v ,w along-axis, cross-axis, and vertical velocity components, sonic output, in metres per second

a a a
u ,v ,w nth sample of u ,v ,w , in metres per second
a,n a,n a,n a a a
© ISO 2002 – All rights reserved 3
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ISO 16622:2002(E)
v along-path velocity component of the wind, in metres per second
v cross-path velocity component of the wind, in metres per second
v wind speed at the location of the sound path (vv=+v )
tn d
α wind direction, reference sensor output, in degrees

α azimuth of the undisturbed flow with respect to the sonic orientation — either equal to the wind tunnel

axis azimuth relative to the sonic azimuth, or azimuth measured by a reference sensor, in degrees

α wind direction, sonic output, in degrees, with sonic azimuth a
α wind direction, sonic output, in degrees, with sonic azimuth b
α nth sample of α
a,n a
α vectorial average of α , in degrees
v a
α scalar average of α , in degrees
s a

∆ modulus of the vector difference between measured and undisturbed wind tunnel velocity at azimuth

α, in metres per second

∆ modulus of the vector difference between the wind vectors measured in the zero wind chamber with

a,b
the instrument azimuths α and α , in metres per second
a b

∆ modulus of the vector difference between the nth and the mth sample of the wind vector measured in

a,n,m
the zero wind chamber with the instrument azimuth α

ϕ the tilt of the sensor relative to the horizontal wind tunnel airflow, in degrees; positive angles are the

fixture axis above the horizontal on the upwind side, and negative angles are the fixture axis below

the horizontal
ρ air density, in kilograms per cubic metre
Ω angular velocity azimuth rotation of the sensor, in degrees per second
5 Summary of methods

The instrument's array should be examined for damage and conformance with manufacturer design specifications

prior to testing. The accuracy of all measurements and results shall be ascertained and reported in accordance

with ISO 5725-1 and ISO 5725-2.

 Zero wind chamber test: the offset of the measured wind speed is determined over the operational

temperature range.

 Wind tunnel test: the deviation of the measured from the true velocity (vector) is determined over the

operational range of flow speed and direction.

 Pressure chamber test: the operational range of air density is determined. Although the measuring principle

does not depend on air density, a minimum density is required to transmit detectable sound.

 Field test: addresses the response to potentially adverse environmental conditions, which are difficult to

simulate in the laboratory.
4 © ISO 2002 – All rights reserved
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ISO 16622:2002(E)
6 Array examination prior to testing

Ensure that the array is properly oriented and aligned, and is free of damage or obstruction.

Measure and record the path lengths between transducer pairs and compare to manufacturer-specified path

lengths and tolerances, if available. If the results exceed manufacturer's tolerances, terminate the procedure.

7 Zero wind chamber test
7.1 Purpose

The purpose of the zero wind chamber test is to define the magnitude of the zero offset and/or instrument

alignment or calibration problems.

The system delay (3.6) consists of signal propagation times within the transducers and the electronics. The

asymmetric part of the system delay (that is, the difference of delays between both signal propagation directions)

causes a zero offset of the corresponding wind component. Usually the zero offset is largely eliminated by the on-

line signal processing, based on a factory calibration. Nevertheless, the offset can drift with time and it may be

temperature dependent. It can be determined by testing the array into a zero wind chamber (see annex A).

7.2 Procedure
7.2.1 Obtain zero wind chamber performance standards from manufacturer.

7.2.2 Place the array in the zero wind chamber and wait for the internal chamber temperature and air movement

to stabilize. Make sure that the anemometer is operating but that array heating, if any, is off.

7.2.3 Set the sonic averaging interval to the same that is used for the application. Make sure that the chamber

fan, if used, is switched off.

7.2.4 Read and record the temperature, the wind velocity and direction or wind components measured by the

sonic ⇒ U α or ⇒ u v w . Index a denotes the azimuth orientation of the instrument in the zero wind

a,n a,n a,n a,n a,n
chamber, and index n denotes the number of the sample.

7.2.5 Repeat 7.2.4 at least three times at 10-min intervals. If all measured wind speeds are within the

instrument's specified zero offset, accept. Report the chamber temperature, because the offset may be

temperature dependent. If the zero wind chamber design is approved by the manufacturer, and if one or more

samples of the measured wind speeds exceed the instrument's specified zero offset, reject.

7.2.6 If a zero wind chamber design is used, which is not approved by the manufacturer, and if one or more

samples of the measured wind speeds exceed the instrument specifications, make sure that the variability is not

due to some residual air motion in the test chamber. For this purpose calculate the modulus of the vector

differences.
∆α=−(sUUin sinαα)+(U cos−U cosα ) (2)
an,,m a,n a,n a,m a,m a,n a,n a,m a,m

where ∆ is the modulus of the vector difference between the nth and the mth sample of the wind vector with the

a,n,m
instrument azimuth α.

If the maximum of ∆ is less than 10 % of the instrument's zero offset specification, the offset is stable with time,

a,n,m

and air motion can be excluded. Now make sure that the offset is not caused by wall reflections. For this purpose

rotate the array around its azimuth axis relative to the chamber by about half the symmetry angle of the array (60°

for an array with 120° symmetry) and wait again for the air movement to stabilize. Read and record again the wind

velocity and direction ⇒ U , α .
b b
© ISO 2002 – All rights reserved 5
---------------------- Page: 10 ----------------------
ISO 16622:2002(E)

a) Without wall reflections, the zero offset is independent of the azimuth orientation of the array in the chamber

(designated by the indices a and b). In that case the modulus of the vector difference ∆ from equation (3) is

a,b

small [less than 10 % of (U + U )/2]. If this is the case, the observed zero offsets are real and are not artifacts.

a b
Reject.
∆α=−(UUsin sinα )+ (U cosα−U cosα ) (3)
ab, a a b b a a b b

b) With wall reflections, the zero offset depends on the azimuth orientation of the array in the chamber, and ∆

ab,
is not small. Redesign the zero wind test chamber.

If the maximum of ∆ [equation (2)] is not small compared to the instrument's specified zero offset, either the

a,n,m

sonic is unstable or there is too much air motion in the test chamber. Ensure that the zero wind chamber is in

thermal equilibrium.

7.2.7 Repeat the zero offset test at the upper and lower limits of the operational temperature range. For this

purpose a temperature chamber that accommodates the zero wind test chamber and the sonic electronics is

required.

Test at the lower temperature limit: The zero offset does not depend on the air temperature but on the transducer

and electronic temperatures. If the sonic has a transducer heating system which is usually activated at low

temperatures, the allowable transducer temperature may be higher than the specified minimum ambient

temperature. As the heating should be switched off during the zero wind test, the lower temperature limit of the

temperature chamber should be set to the lowest allowable transducer temperature.

8 Wind tunnel test
8.1 Purpose

To test for deviation of test instrument velocity measurements from known wind tunnel velocities.

While the ideal response function of a sonic (for one wind component) is given by equation (B.2), the real response

function shows deviations from this equation. These deviations consist of a zero offset, which is described in

clause 7, and errors due to flow distortions and shadows, which can be quantified by comparing the wind speed

and direction, indicated by the sonic, with the undisturbed wind tunnel speed and the orientation of the sonic

azimuth relative to the wind tunnel axis, respectively. Usually the errors due to flow distortions and shadows are

reduced by the application of corrections during the on-line signal processing (see annex B).

The errors depend on speed, azimuth and tilt angle ϕ of the flow. Therefore, a complete test would require a

very large number of (time-consuming) measurements. For acceptance test purposes a simplified procedure is

described, which makes use of the fact that the maximum and minimum relative errors usually occur at nearly the

same azimuth and elevation over a broad range of flow speeds.

Minimum requirements for the wind tunnel used for the acceptance test are set out in annex C.

8.2 Precaution

In wind tunnels with closed test sections reflections from the walls may cause errors (see also clause 7). The

purpose of the following procedure is to quantify the reflection error. Prior to this procedure, the zero wind chamber

test shall be passed successfully. The procedure chosen depends on the lowest speed that is possible in the wind

tunnel (residual motion, if the tunnel is shut off).

a) The wind tunnel speed can be set to values lower than the zero offset specified for the instrument.

1) Read and record the measured wind velocity U for five azimuth angles α of the sonic within half the

a a

symmetry angle of the array (e.g. α = 0°, α = 15°, α = 30°, α = 45°, α = 60° for 120° array-symmetry).

1 2 3 4 5
6 © ISO 2002 – All rights reserved
---------------------- Page: 11 ----------------------
ISO 16622:2002(E)

2) If all values of U are equal or below the allowable offset, errors by reflections may be excluded.

b) The wind tunnel speed cannot be set to values lower than the zero offset specified for the instrument.

1) Set the tunnel speed U to the lowest possible value with well-defined speed and direction.

2) Record the measured wind velocity and direction (U , α ) for five azimuth angles α of the sonic within half

a a a
the symmetry angle of the array.

3) Calculate the modulus of the vector difference to the undisturbed wind tunnel velocity

∆α=−(UUsin sinα )+ (U cosα−U cosα ) (4)
aa a 00 a a 0 0

where ∆ is the sum of all errors including zero offset, flow distortion and reflection.

4) Evaluate the distribution of ∆ for all five α . If the differences are within 10 % of the average, errors due to

a a
reflection may be excluded.

NOTE Since the flow distortion error increases with increasing wind speed, the procedure is only applicable at low wind

speeds at which, according to the instrument specifications, flow distortion errors are safely below the zero offset.

8.3 Procedure
8.3.1 Variation of wind direction at fixed speeds

The error of wind speed U and wind direction α versus true wind direction is measured by varying the sonic

a a

orientation with respect to the air flow at discrete wind tunnel speeds. Rotate the sonic in 5°-increments or smaller

around the full 360° circle. Average each data point over 30 s or longer. The averaging may be performed off-line in

order to obtain the confidence interval of each data point from the statistical distribution of the samples. Conduct

the direction test at a minimum of five fixed speeds over the full operation range from U to U . Use a speed

min max

distribution approximately equidistant in a logarithmic scale. Recommended wind tunnel speeds (as percent of

U ) are:
max
10 %; 18 %; 32 %; 56 %; 100 %.

Set the wind tunnel speed to a known value, to the maximum accuracy of the wind tunnel, and to within 10 %

deviation of the above listed values.

Analyse the directional test data for the worst and best case orientations (maximum and minimum bias). Usually

the worst and best case orientations do not depend on the speed.

NOTE Generally the worst and best orientations are different for speed bias and direction bias. For some sonic designs, the

worst orientation for direction bias coincides with best orientation for speed bias, and vice versa.

8.3.2 Variation of wind speeds at the worst- and best-case orientation(s)

The bias versus wind speed is measured by varying the wind-tunnel speed at the worst- and best-case orientations

of the sonic. If multiple worst- and best-case orientations have been found for different speed ranges, conduct

complete runs for each orientation. Obtain (at least) 30 s data-point averages. The averaging may be performed

off-line in order to obtain the confidence interval from the statistical distribution of the samples. Acquire the data at

ten speeds distributed over the operational range. Use a speed distribution approximately equidistant in a

logarithmic scale, (and U should be at the lowest speed at which stable wind tunnel flowrates can be

min

maintained) starting with 1 % of U as the minimum speed. Recommended wind tunnel speeds (as percent of

max
U ) are:
max
1,0 %; 1,7 %; 2,8 %; 4,6 %; 7,7 %; 13 %; 21 %; 36 %; 60 %; 100 %.
© ISO 2002 – All rights reserved 7
---------------------- Page: 12 ----------------------
ISO 16622:2002(E)

For some wind tunnels, 1 % of U is below the specified minimum speed of the wind tunnel. In that case, the

max
following speed distribution (as percent of U ) is recommended:
max
2,0 %; 3,0 %; 5,0 %; 7,0 %; 11 %; 18 %; 27 %; 42 %; 65 %; 100 %.
8.3.3 Off-axis response

Repeat the procedures in 8.3.1 and 8.3.2 with the sonic azimuth axis tilted 15° upwind and 15° downwind.

If the sonic is designed to measure the speed of the horizontal components of the wind vector, compare U with U

a 0
cos ϕ, where ϕ is the tilt angle.
If the sonic is designed to measure the speed of the three-dimensional wind
...

SLOVENSKI STANDARD
SIST ISO 16622:2004
01-junij-2004
0HWHRURORJLMD±=YRþQLDQHPRPHWULWHUPRPHWUL±3UHVNXVVSUHMHPOMLYRVWLPHWRGH
]DGRORþDQMHSRYSUHþQHYUHGQRVWLYHWUD
Meteorology - Sonic anemometers/thermometers - Acceptance test methods for mean
wind measurements

Météorologie - Anémomètres/thermomètres soniques - Méthodes d'essai d'acceptation

pour les mesurages de la vitesse moyenne du vent
Ta slovenski standard je istoveten z: ISO 16622:2002
ICS:
07.060 Geologija. Meteorologija. Geology. Meteorology.
Hidrologija Hydrology
SIST ISO 16622:2004 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST ISO 16622:2004
---------------------- Page: 2 ----------------------
SIST ISO 16622:2004
INTERNATIONAL ISO
STANDARD 16622
First edition
2002-09-15
Meteorology — Sonic
anemometers/thermometers — Acceptance
test methods for mean wind measurements
Météorolgie — Anémomètres/thermomètres soniques — Méthodes d'essai
d'acceptation pour les mesurages de la vitesse moyenne du vent
Reference number
ISO 16622:2002(E)
ISO 2002
---------------------- Page: 3 ----------------------
SIST ISO 16622:2004
ISO 16622:2002(E)
PDF disclaimer

This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but shall not

be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this

file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat accepts no liability in this

area.
Adobe is a trademark of Adobe Systems Incorporated.

Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters

were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event

that a problem relating to it is found, please inform the Central Secretariat at the address given below.

© ISO 2002

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic

or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO's member body

in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.ch
Web www.iso.ch
Printed in Switzerland
ii © ISO 2002 – All rights reserved
---------------------- Page: 4 ----------------------
SIST ISO 16622:2004
ISO 16622:2002(E)
Contents Page

Foreword .................................................................................................................................................................... iv

Introduction................................................................................................................................................................. v

1 Scope.............................................................................................................................................................. 1

2 Normative references.................................................................................................................................... 1

3 Terms and definitions................................................................................................................................... 1

4 Symbols and abbreviated terms.................................................................................................................. 3

5 Summary of methods.................................................................................................................................... 4

6 Array examination prior to testing .............................................................................................................. 5

7 Zero wind chamber test................................................................................................................................ 5

7.1 Purpose .......................................................................................................................................................... 5

7.2 Procedure....................................................................................................................................................... 5

8 Wind tunnel test ............................................................................................................................................ 6

8.1 Purpose .......................................................................................................................................................... 6

8.2 Precaution...................................................................................................................................................... 6

8.3 Wind tunnel test procedure.......................................................................................................................... 7

9 Pressure chamber test (optional) ................................................................................................................ 9

9.1 Purpose .......................................................................................................................................................... 9

9.2 Apparatus..................................................................................................................................................... 10

9.3 Procedure..................................................................................................................................................... 10

10 Field tests..................................................................................................................................................... 10

10.1 Purpose ........................................................................................................................................................ 10

10.2 Duration........................................................................................................................................................ 10

10.3 Siting............................................................................................................................................................. 10

10.4 Field site equipment.................................................................................................................................... 11

10.5 Evaluation .................................................................................................................................................... 11

Annex A (informative) Zero wind chamber.............................................................................................................13

Annex B (informative) Wind measurement with sonics........................................................................................ 14

Annex C (normative) Wind tunnel........................................................................................................................... 18

Annex D (informative) Acoustic impedance versus altitude................................................................................ 20

Bibliography.............................................................................................................................................................. 21

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SIST ISO 16622:2004
ISO 16622:2002(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO

member bodies). The work of preparing International Standards is normally carried out through ISO technical

committees. Each member body interested in a subject for which a technical committee has been established has

the right to be represented on that committee. International organizations, governmental and non-governmental, in

liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical

Commission (IEC) on all matters of electrotechnical standardization.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.

The main task of technical committees is to prepare International Standards. Draft International Standards adopted

by the technical committees are circulated to the member bodies for voting. Publication as an International

Standard requires approval by at least 75 % of the member bodies casting a vote.

Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights.

ISO 16622 was prepared by Technical Committee ISO/TC 146, Air quality, Subcommittee SC 5, Meteorology.

Annex C forms a normative part of this International Standard. Annexes A, B and D are for information only.

iv © ISO 2002 – All rights reserved
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ISO 16622:2002(E)
Introduction

Most human activity influencing the dispersion of anthropogenic pollutants occurs within the surface layer (SL), that

portion of the atmosphere which lies within a few tens of metres of the earth's surface. The SL is typified by sharp

gradients and time-varying fluxes of heat, moisture and momentum. Three-dimensional flow and turbulence

information resolved over short temporal and spatial scales is needed to characterize the SL. This information must

be presented not only as time-mean quantities, but also as the turbulent fluctuations of those quantities which

contribute to the production, transport, dispersion and dissipation processes operating within the SL. The sonic

anemometer/thermometer (shortened to “sonic” in the following) is an instrument well suited to obtain

measurements necessary for SL characterization.

A sonic consists of a transducer array containing paired sets of ultrasonic transmitter/receivers, and circuitry

designed to measure the transit times of acoustic waves propagating over the path (typically 10 cm – 20 cm)

between transducer pairs. A three-dimensional array resolves horizontal and vertical wind components plus the

speed of sound from which the sonic (virtual) temperature can be derived. Sonic anemometry has been used for

several decades in atmospheric research, but recent advances in instrument design and signal processing,

coupled with increased sophistication of atmospheric dispersion models, has led to an increasing demand for their

use, including routine wind speed and direction measurements. Because they contain no moving parts, sonics offer

low maintenance and operational advantages in adverse weather conditions. These factors have stimulated the

commercial manufacture of sonics and the drafting of several national sonic standards which form the basis for the

following International Standard of performance measurements and test methods.

The procedures presented in this document define methods for acceptance testing of sonics to be used for mean

wind measurements. Minimum requirements for conformance with this International Standard include successful

completion of the zero wind chamber test (clause 7), the wind tunnel test (clause 8), and the field test (clause 10).

The pressure chamber test (clause 9) is recommended if the sonic is to be used at elevations higher than 2 000 m

above mean sea level.
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SIST ISO 16622:2004
INTERNATIONAL STANDARD ISO 16622:2002(E)
Meteorology — Sonic anemometers/thermometers — Acceptance
test methods for mean wind measurements
1 Scope

This International Standard defines test methods of the performance of sonic anemometers/thermometers which

employ the inverse time measurement for velocity of sound along differently oriented paths. It is applicable to

designs measuring two or three components of the wind vector within an unlimited (360°) azimuthal acceptance

angle.
2 Normative references

The following normative documents contain provisions which, through reference in this text, constitute provisions of

this International Standard. For dated references, subsequent amendments to, or revisions of, any of these

publications do not apply. However, parties to agreements based on this International Standard are encouraged to

investigate the possibility of applying the most recent editions of the normative documents indicated below. For

undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC

maintain registers of currently valid International Standards.

ISO 5725-1, Accuracy (trueness and precision) of measurement methods and results — Part 1: General principles

and definitions

ISO 5725-2, Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic method for

the determination of repeatability and reproducibility of a standard measurement method

ASTM D5741-96, Standard Practice for Characterizing Surface Wind Using a Wind Vane and Rotating

Anemometer

WMO CIMO, 1996 World Meteorological Organization (ed.) Guide to meteorological instruments and methods of

observation. WMO-No.8, 6th edn. 1996, Geneva
3 Terms and definitions

For the purposes of this International Standard, the following terms and definitions apply.

3.1
array

mechanical structure to support the sonic transducers in the desired geometric configuration

3.2
array symmetry angle
angular distance about which the array is symmetrical
3.3
mean
mean value over the (selected) averaging interval of the sonic
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SIST ISO 16622:2004
ISO 16622:2002(E)
3.4
sonic
sonic anemometer/thermometer

instrument consisting of a transducer array containing sets of acoustic transmitters and receivers, a system clock,

and microprocessor circuitry to measure intervals of time between the transmission and reception of sound pulses

3.5
sound path
path between a pair of transducers
3.6
system delay

difference between the electronically detected total propagation time and the transit time

NOTE The time between the electronic generation of the transmission signal and the electronic detection of the received

signal is longer than the transit time due to the propagation times through the transducers and the electronic circuitry.

3.7
transit time
time required by a sound wave front to propagate between a pair of transducers
3.8
turbulence level
turbulence intensity
ratio of the square root of the turbulent kinetic energy to the mean wind speed
22 2
′′ ′
uv++w
T = (1)
where
′ denotes deviations from the mean.
EXAMPLE uu=−u , etc., where
u is the instantaneous wind component
u is the mean wind component.
3.9
zero offset
wind speed indicated by the sonic in calm air
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ISO 16622:2002(E)
4 Symbols and abbreviated terms
T temperature, in kelvin
T sonic temperature, in kelvin [see equation (B.4)]
T turbulence intensity

U speed of the undisturbed flow in the wind tunnel, speed, or wind speed measured by a reference

sensor, in metres per second
U wind speed, sonic output, in metres per second with sonic azimuth a
U wind speed, sonic output, in metres per second with sonic azimuth b
U nth sample of U , in metres per second
a,n a
U vectorial average of U , in metres per second
v a
U scalar average of U , in metres per second
s a
U specified maximum speed measurable with the sonic, in metres per second
max
U minimum test speed, in metres per second
min
−2 −1
Z acoustic impedance (Z = ρ⋅c [kg⋅m ⋅s ])
a sonic azimuth, in degrees
b sonic azimuth, in degrees
c speed of sound, in metres per second
d path length, in metres
e water vapour partial pressure, in hectopascals
h height above mean sea level, in metres
p pressure, in hectopascals
p equivalent pressure, in hectopascals (see Table D.1)
t averaging interval, in seconds
t transit time from transducer+ to transducer− , in seconds
t transit time from transducer− to transducer+ , in seconds

u ,v ,w along-axis, cross-axis, and vertical velocity components of the undisturbed flow, in metres per second

0 0 0

u ,v ,w along-axis, cross-axis, and vertical velocity components, sonic output, in metres per second

a a a
u ,v ,w nth sample of u ,v ,w , in metres per second
a,n a,n a,n a a a
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v along-path velocity component of the wind, in metres per second
v cross-path velocity component of the wind, in metres per second
v wind speed at the location of the sound path (vv=+v )
tn d
α wind direction, reference sensor output, in degrees

α azimuth of the undisturbed flow with respect to the sonic orientation — either equal to the wind tunnel

axis azimuth relative to the sonic azimuth, or azimuth measured by a reference sensor, in degrees

α wind direction, sonic output, in degrees, with sonic azimuth a
α wind direction, sonic output, in degrees, with sonic azimuth b
α nth sample of α
a,n a
α vectorial average of α , in degrees
v a
α scalar average of α , in degrees
s a

∆ modulus of the vector difference between measured and undisturbed wind tunnel velocity at azimuth

α, in metres per second

∆ modulus of the vector difference between the wind vectors measured in the zero wind chamber with

a,b
the instrument azimuths α and α , in metres per second
a b

∆ modulus of the vector difference between the nth and the mth sample of the wind vector measured in

a,n,m
the zero wind chamber with the instrument azimuth α

ϕ the tilt of the sensor relative to the horizontal wind tunnel airflow, in degrees; positive angles are the

fixture axis above the horizontal on the upwind side, and negative angles are the fixture axis below

the horizontal
ρ air density, in kilograms per cubic metre
Ω angular velocity azimuth rotation of the sensor, in degrees per second
5 Summary of methods

The instrument's array should be examined for damage and conformance with manufacturer design specifications

prior to testing. The accuracy of all measurements and results shall be ascertained and reported in accordance

with ISO 5725-1 and ISO 5725-2.

 Zero wind chamber test: the offset of the measured wind speed is determined over the operational

temperature range.

 Wind tunnel test: the deviation of the measured from the true velocity (vector) is determined over the

operational range of flow speed and direction.

 Pressure chamber test: the operational range of air density is determined. Although the measuring principle

does not depend on air density, a minimum density is required to transmit detectable sound.

 Field test: addresses the response to potentially adverse environmental conditions, which are difficult to

simulate in the laboratory.
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ISO 16622:2002(E)
6 Array examination prior to testing

Ensure that the array is properly oriented and aligned, and is free of damage or obstruction.

Measure and record the path lengths between transducer pairs and compare to manufacturer-specified path

lengths and tolerances, if available. If the results exceed manufacturer's tolerances, terminate the procedure.

7 Zero wind chamber test
7.1 Purpose

The purpose of the zero wind chamber test is to define the magnitude of the zero offset and/or instrument

alignment or calibration problems.

The system delay (3.6) consists of signal propagation times within the transducers and the electronics. The

asymmetric part of the system delay (that is, the difference of delays between both signal propagation directions)

causes a zero offset of the corresponding wind component. Usually the zero offset is largely eliminated by the on-

line signal processing, based on a factory calibration. Nevertheless, the offset can drift with time and it may be

temperature dependent. It can be determined by testing the array into a zero wind chamber (see annex A).

7.2 Procedure
7.2.1 Obtain zero wind chamber performance standards from manufacturer.

7.2.2 Place the array in the zero wind chamber and wait for the internal chamber temperature and air movement

to stabilize. Make sure that the anemometer is operating but that array heating, if any, is off.

7.2.3 Set the sonic averaging interval to the same that is used for the application. Make sure that the chamber

fan, if used, is switched off.

7.2.4 Read and record the temperature, the wind velocity and direction or wind components measured by the

sonic ⇒ U α or ⇒ u v w . Index a denotes the azimuth orientation of the instrument in the zero wind

a,n a,n a,n a,n a,n
chamber, and index n denotes the number of the sample.

7.2.5 Repeat 7.2.4 at least three times at 10-min intervals. If all measured wind speeds are within the

instrument's specified zero offset, accept. Report the chamber temperature, because the offset may be

temperature dependent. If the zero wind chamber design is approved by the manufacturer, and if one or more

samples of the measured wind speeds exceed the instrument's specified zero offset, reject.

7.2.6 If a zero wind chamber design is used, which is not approved by the manufacturer, and if one or more

samples of the measured wind speeds exceed the instrument specifications, make sure that the variability is not

due to some residual air motion in the test chamber. For this purpose calculate the modulus of the vector

differences.
∆α=−(sUUin sinαα)+(U cos−U cosα ) (2)
an,,m a,n a,n a,m a,m a,n a,n a,m a,m

where ∆ is the modulus of the vector difference between the nth and the mth sample of the wind vector with the

a,n,m
instrument azimuth α.

If the maximum of ∆ is less than 10 % of the instrument's zero offset specification, the offset is stable with time,

a,n,m

and air motion can be excluded. Now make sure that the offset is not caused by wall reflections. For this purpose

rotate the array around its azimuth axis relative to the chamber by about half the symmetry angle of the array (60°

for an array with 120° symmetry) and wait again for the air movement to stabilize. Read and record again the wind

velocity and direction ⇒ U , α .
b b
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a) Without wall reflections, the zero offset is independent of the azimuth orientation of the array in the chamber

(designated by the indices a and b). In that case the modulus of the vector difference ∆ from equation (3) is

a,b

small [less than 10 % of (U + U )/2]. If this is the case, the observed zero offsets are real and are not artifacts.

a b
Reject.
∆α=−(UUsin sinα )+ (U cosα−U cosα ) (3)
ab, a a b b a a b b

b) With wall reflections, the zero offset depends on the azimuth orientation of the array in the chamber, and ∆

ab,
is not small. Redesign the zero wind test chamber.

If the maximum of ∆ [equation (2)] is not small compared to the instrument's specified zero offset, either the

a,n,m

sonic is unstable or there is too much air motion in the test chamber. Ensure that the zero wind chamber is in

thermal equilibrium.

7.2.7 Repeat the zero offset test at the upper and lower limits of the operational temperature range. For this

purpose a temperature chamber that accommodates the zero wind test chamber and the sonic electronics is

required.

Test at the lower temperature limit: The zero offset does not depend on the air temperature but on the transducer

and electronic temperatures. If the sonic has a transducer heating system which is usually activated at low

temperatures, the allowable transducer temperature may be higher than the specified minimum ambient

temperature. As the heating should be switched off during the zero wind test, the lower temperature limit of the

temperature chamber should be set to the lowest allowable transducer temperature.

8 Wind tunnel test
8.1 Purpose

To test for deviation of test instrument velocity measurements from known wind tunnel velocities.

While the ideal response function of a sonic (for one wind component) is given by equation (B.2), the real response

function shows deviations from this equation. These deviations consist of a zero offset, which is described in

clause 7, and errors due to flow distortions and shadows, which can be quantified by comparing the wind speed

and direction, indicated by the sonic, with the undisturbed wind tunnel speed and the orientation of the sonic

azimuth relative to the wind tunnel axis, respectively. Usually the errors due to flow distortions and shadows are

reduced by the application of corrections during the on-line signal processing (see annex B).

The errors depend on speed, azimuth and tilt angle ϕ of the flow. Therefore, a complete test would require a

very large number of (time-consuming) measurements. For acceptance test purposes a simplified procedure is

described, which makes use of the fact that the maximum and minimum relative errors usually occur at nearly the

same azimuth and elevation over a broad range of flow speeds.

Minimum requirements for the wind tunnel used for the acceptance test are set out in annex C.

8.2 Precaution

In wind tunnels with closed test sections reflections from the walls may cause errors (see also clause 7). The

purpose of the following procedure is to quantify the reflection error. Prior to this procedure, the zero wind chamber

test shall be passed successfully. The procedure chosen depends on the lowest speed that is possible in the wind

tunnel (residual motion, if the tunnel is shut off).

a) The wind tunnel speed can be set to values lower than the zero offset specified for the instrument.

1) Read and record the measured wind velocity U for five azimuth angles α of the sonic within half the

a a

symmetry angle of the array (e.g. α = 0°, α = 15°, α = 30°, α = 45°, α = 60° for 120° array-symmetry).

1 2 3 4 5
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2) If all values of U are equal or below the allowable offset, errors by reflections may be excluded.

b) The wind tunnel speed cannot be set to values lower than the zero offset specified for the instrument.

1) Set the tunnel speed U to the lowest possible value with well-defined speed and direction.

2) Record the measured wind velocity and direction (U , α ) for five azimuth angles α of the sonic within half

a a a
the symmetry angle of the array.

3) Calculate the modulus of the vector difference to the undisturbed wind tunnel velocity

∆α=−(UUsin sinα )+ (U cosα−U cosα ) (4)
aa a 00 a a 0 0

where ∆ is the sum of all errors including zero offset, flow distortion and reflection.

4) Evaluate the distribution of ∆ for all five α . If the differences are within 10 % of the average, errors due to

a a
reflection may be excluded.

NOTE Since the flow distortion error increases with increasing wind speed, the procedure is only applicable at low wind

speeds at which, according to the instrument specifications, flow distortion errors are safely below the zero offset.

8.3 Procedure
8.3.1 Variation of wind direction at fixed speeds

The error of wind speed U and wind direction α versus true wind direction is measured by varying the sonic

a a

orientation with respect to the air flow at discrete wind tunnel speeds. Rotate the sonic in 5°-increments or smaller

around the full 360° circle. Average each data point over 30 s or longer. The averaging may be performed off-line in

order to obtain the confidence interval of each data point from the statistical distribution of the samples. Conduct

the direction test at a minimum of five fixed speeds over the full operation range from U to U . Use a speed

min max

distribution approximately equidistant in a logarithmic scale. Recommended wind tunnel speeds (as percent of

U ) are:
max
10 %; 18 %; 32 %; 56 %; 100 %.

Set the wind tunnel speed to a known value, to the maximum accuracy of the wind tunnel, and to within 10 %

deviation of the above listed values.

Analyse the directional test data for the worst and best case orientations (maximum and minimum bias). Usually

the worst and best case orientations do not depend on the speed.

NOTE Generally the worst and best orientations are different for speed bias and direction bias. For some sonic designs, the

worst orientation for direction bias coincides with best orientation for speed bias, and vice versa.

8.3.2 Variation of wind speeds at the worst- and best-case orientation(s)

The bias versus wind speed is measured by varying the wind-tunnel speed at the worst- and best-case orientations

of the sonic. If multiple worst- and best-case orientations have been found for different speed ranges, conduct

complete runs for each orientation. Obtain (at least) 30 s data-point averages. The averaging may be performed

off-line in order to obtain the confidence interval from the statistical distribution of the

...

NORME ISO
INTERNATIONALE 16622
Première édition
2002-09-15
Météorologie —
Anémomètres/thermomètres soniques —
Méthodes d'essai d'acceptation pour les
mesurages de la vitesse moyenne du vent
Meteorology — Sonic anemometers/thermometers — Acceptance test
methods for mean wind measurements
Numéro de référence
ISO 16622:2002(F)
ISO 2002
---------------------- Page: 1 ----------------------
ISO 16622:2002(F)
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ISO 16622:2002(F)
Sommaire Page

Avant-propos ............................................................................................................................................................. iv

Introduction................................................................................................................................................................. v

1 Domaine d'application .................................................................................................................................. 1

2 Références normatives................................................................................................................................. 1

3 Termes et définitions .................................................................................................................................... 1

4 Symboles et termes abrégés ....................................................................................................................... 3

5 Résumé des méthodes ................................................................................................................................. 4

6 Examen du support avant les essais .......................................................................................................... 5

7 Essai en enceinte pour vent nul .................................................................................................................. 5

7.1 Objectif de l’essai.......................................................................................................................................... 5

7.2 Mode opératoire ............................................................................................................................................ 5

8 Essai en soufflerie......................................................................................................................................... 6

8.1 Objectif de l’essai.......................................................................................................................................... 6

8.2 Précaution...................................................................................................................................................... 7

8.3 Mode opératoire ............................................................................................................................................ 7

9 Essai en chambre de compression (facultatif) ........................................................................................ 10

9.1 Objectif de l’essai........................................................................................................................................ 10

9.2 Appareillage................................................................................................................................................. 10

9.3 Mode opératoire .......................................................................................................................................... 10

10 Essais sur le terrain .................................................................................................................................... 11

10.1 Objectif de l’essai........................................................................................................................................ 11

10.2 Durée de l’essai ........................................................................................................................................... 11

10.3 Choix du site................................................................................................................................................ 11

10.4 Matériel du site d’essai............................................................................................................................... 11

10.5 Évaluation .................................................................................................................................................... 12

Annexe A (informative) Enceinte pour vent nul..................................................................................................... 14

Annexe B (informative) Mesurage du vent à l'aide de soniques.......................................................................... 15

Annexe C (normative) Soufflerie............................................................................................................................. 19

Annexe D (informative) Impédance acoustique par rapport à l'altitude.............................................................. 21

Bibliographie............................................................................................................................................................. 22

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ISO 16622:2002(F)
Avant-propos

L'ISO (Organisation internationale de normalisation) est une fédération mondiale d'organismes nationaux de

normalisation (comités membres de l'ISO). L'élaboration des Normes internationales est en général confiée aux

comités techniques de l'ISO. Chaque comité membre intéressé par une étude a le droit de faire partie du comité

technique créé à cet effet. Les organisations internationales, gouvernementales et non gouvernementales, en

liaison avec l'ISO participent également aux travaux. L'ISO collabore étroitement avec la Commission

électrotechnique internationale (CEI) en ce qui concerne la normalisation électrotechnique.

Les Normes internationales sont rédigées conformément aux règles données dans les Directives ISO/CEI,

Partie 3.

La tâche principale des comités techniques est d'élaborer les Normes internationales. Les projets de Normes

internationales adoptés par les comités techniques sont soumis aux comités membres pour vote. Leur publication

comme Normes internationales requiert l'approbation de 75 % au moins des comités membres votants.

L’attention est appelée sur le fait que certains des éléments de la présente Norme internationale peuvent faire

l’objet de droits de propriété intellectuelle ou de droits analogues. L’ISO ne saurait être tenue pour responsable de

ne pas avoir identifié de tels droits de propriété et averti de leur existence.

La Norme internationale ISO 16622 a été élaborée par le comité technique ISO/TC 146, Qualité de l'air,

sous-comité SC 5, Météorologie.

L’annexe C constitue un élément normatif de la présente Norme internationale. Les annexes A, B et D sont

données uniquement à titre d’information.
iv © ISO 2002 – Tous droits réservés
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ISO 16622:2002(F)
Introduction

La majeure partie de l’activité humaine influant sur la dispersion de polluants a lieu dans la couche limite (SL),

partie de l’atmosphère qui s’étend sur quelques dizaines de mètres au-dessus de la surface terrestre. Cette

couche se caractérise par de forts gradients et des variations, dans le temps, de la température, de l’humidité et du

niveau de turbulence. Afin d’établir les caractéristiques de la couche limite, des données relatives aux flux et

turbulences tridimensionnels établies sur des échelles de temps et d’espace restreintes sont nécessaires. Ces

données doivent être présentées non seulement sous la forme de grandeurs moyennes intégrées dans le temps,

mais également sous la forme des fluctuations de ces grandeurs dont la turbulence contribue aux processus de

production, de transport, de dispersion et de dissipation qui ont lieu dans la couche limite. L’anémomètre/

thermomètre sonique (appelé «sonique» dans le reste de la présente Norme internationale) est un instrument qui

convient bien à l’obtention de valeurs de mesures nécessaires à la caractérisation de la couche limite.

Un sonique se compose d’un support de transducteurs portant des couples de transmetteurs/récepteurs à

ultrasons et d’un circuit conçu pour mesurer les temps de parcours des ondes acoustiques se propageant sur la

distance qui sépare les couples de transducteurs (généralement 10 cm à 20 cm). Un support tridimensionnel

permet d’établir les composantes horizontales et verticales du vent ainsi que la vitesse du son à partir de laquelle

la température sonique (virtuelle) peut être dérivée. L’anémométrie sonique est utilisée depuis des décennies dans

les recherches sur l’atmosphère mais les récentes avancées dans la conception des instruments et le traitement

du signal, associées à une sophistication accrue des modèles de dispersion atmosphérique ont conduit à une

demande croissante, notamment pour les mesures classiques de vitesse et direction du vent. Puisqu’ils ne

comprennent pas de pièces mobiles, les soniques demandent peu d’entretien et ont l’avantage d’être faciles

d’utilisation, même dans des conditions climatiques défavorables. Ces facteurs ont favorisé le développement

commercial des soniques et la préparation de normes nationales sur lesquelles se base la présente Norme

internationale relative aux mesurages des performances et aux méthodes d’essai applicables aux soniques.

Les modes opératoires décrits dans le présent document définissent les méthodes d’essais d’acceptation des

soniques utilisés pour les mesurages de la vitesse moyenne du vent. Les exigences minimales de conformité à la

présente Norme internationale impliquent la réussite aux essais en enceinte pour vent nul (article 7), en soufflerie

(article 8) et sur le terrain (article 10). L’essai en chambre de compression (article 9) est recommandé si le sonique

est utilisé à une altitude supérieure à 2 000 m au-dessus du niveau moyen de la mer.

© ISO 2002 – Tous droits réservés v
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NORME INTERNATIONALE ISO 16622:2002(F)
Météorologie — Anémomètres/thermomètres soniques —
Méthodes d'essai d'acceptation pour les mesurages de la vitesse
moyenne du vent
1 Domaine d'application

La présente Norme internationale définit des méthodes d’essai permettant d’évaluer la performance des

anémomètres/thermomètres soniques qui mesurent la vitesse du son le long de trajets à orientations diverses, en

raison inverse du temps. Elle est applicable aux instruments mesurant deux ou trois composantes du vecteur vent

dans un angle d’acceptation azimutal illimité (360°).
2 Références normatives

Les documents normatifs suivants contiennent des dispositions qui, par suite de la référence qui y est faite,

constituent des dispositions valables pour la présente Norme internationale. Pour les références datées, les

amendements ultérieurs ou les révisions de ces publications ne s’appliquent pas. Toutefois, les parties prenantes

aux accords fondés sur la présente Norme internationale sont invitées à rechercher la possibilité d'appliquer les

éditions les plus récentes des documents normatifs indiqués ci-après. Pour les références non datées, la dernière

édition du document normatif en référence s’applique. Les membres de l'ISO et de la CEI possèdent le registre des

Normes internationales en vigueur.

ISO 5725-1, Exactitude (justesse et fidélité) des résultats et méthodes de mesure — Partie 1: Principes généraux

et définitions

ISO 5725-2, Exactitude (justesse et fidélité) des résultats et méthodes de mesure — Partie 2: Méthode de base

pour la détermination de la répétabilité et de la reproductibilité d'une méthode de mesure normalisée

ASTM D5741-96, Standard Practice for Characterizing Surface Wind Using a Wind Vane and Rotating

Anemometer

OMM CIMO, Organisation météorologique mondiale (éd.). Guide des instruments et des méthodes d'observation

météorologiques. OMM-N° 8, 6 édition 1996, Genève
3 Termes et définitions

Pour les besoins de la présente Norme internationale, les termes et définitions suivants s'appliquent.

3.1
support

structure mécanique plaçant les transducteurs soniques dans la configuration géométrique souhaitée

3.2
angle de symétrie du support
distance angulaire par rapport à laquelle le support est symétrique
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ISO 16622:2002(F)
3.3
moyenne
valeur moyenne sur l’intervalle de calcul (sélectionné) du sonique
3.4
sonique
anémomètre/thermomètre sonique

instrument composé d’un support de transducteurs portant des couples de transmetteurs/récepteurs acoustiques,

une horloge intégrée et un microprocesseur avec circuit pour mesurer les laps de temps entre la transmission et la

réception des impulsions acoustiques
3.5
trajet du son
trajet parcouru par le son entre 2 transducteurs
3.6
retard système

différence entre le temps de propagation total détecté électroniquement et le temps de parcours

NOTE La durée s’écoulant entre la génération électronique du signal de transmission et la détection électronique du signal

reçu est plus longue que le temps de parcours en raison des temps de propagation à travers les transducteurs et le circuit

électronique.
3.7
temps de parcours

temps requis par un front d’onde acoustique pour se propager entre 2 transducteurs

3.8
niveau de turbulence
intensité de turbulence

rapport de la racine carrée de l’énergie cinétique turbulente à la vitesse du vent moyenne

22 2
′′ ′
uv++w
T = (1)
où ′ indique les écarts par rapport à la moyenne.
EXEMPLE uu′=−u , etc.
u est la composante vent instantané;
u est la composante vent moyen.
3.9
décalage du zéro
vitesse du vent indiquée par le sonique en l’absence d’air
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ISO 16622:2002(F)
4 Symboles et termes abrégés
T température, en kelvins
T température du sonique, en kelvins [voir équation (B.4)]
T intensité de turbulence

U vitesse du flux laminaire dans la soufflerie, vitesse, ou vitesse du vent mesurée par un capteur de

référence, en mètres par seconde

U vitesse du vent, sortie du sonique, en mètres par seconde, avec azimut d’orientation du sonique a

U vitesse du vent, sortie du sonique, en mètres par seconde, avec azimut d’orientation du sonique b

ème
U n échantillon de U , en mètres par seconde
a,n a
U moyenne vectorielle de U , en mètres par seconde
v a
U moyenne scalaire de U , en mètres par seconde
s a
U vitesse maximale spécifiée mesurable avec un sonique, en mètres par seconde
max
U vitesse minimale d’essai, en mètres par seconde
min
−2 −1
Z impédance acoustique (Z = ρ⋅c [kg⋅m ⋅s ])
a azimut du sonique, en degrés
b azimut du sonique, en degrés
c vitesse du son, en mètres par seconde
d longueur du parcours, en mètres
e pression partielle de la vapeur d’eau, en hectopascals
h hauteur au-dessus du niveau moyen de la mer, en mètres
p pression, en hectopascals
p pression équivalente, en hectopascals (voir Tableau D.1)
t intervalle d’intégration, en secondes
t temps de parcours d’un transducteur+ à un transducteur−, en secondes
t temps de parcours d’un transducteur− à un transducteur+, en secondes

u ,v ,w composantes de vitesse axiale, perpendiculaire et verticale, du flux non perturbé, en mètres par

0 0 0
seconde

u ,v ,w composantes de vitesse axiale, perpendiculaire et verticale, sortie du sonique, en mètres par

a a a
seconde
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ISO 16622:2002(F)
ème
u ,v ,w n échantillon de u , v , w , en mètres par seconde
a,n a,n a,n a a a

v composante de la vitesse dans le sens du vent (ou longitudinale), en mètres par seconde

v composante de la vitesse transversale (perpendiculaire) du vent, en mètres par seconde

22
v vitesse du vent au niveau du trajet du son vv=+v
tn d
α direction du vent, sortie du capteur de référence, en degrés

α azimut du flux non perturbé par rapport à l’orientation du sonique, égal soit à la différence

d’orientation entre l’axe de la soufflerie et le nord du sonique, soit à l’angle mesuré par un capteur de

référence, en degrés
α direction du vent, sortie du sonique, en degrés, avec azimut du sonique a
α direction du vent, sortie du sonique, en degrés, avec azimut du sonique b
ème
α n échantillon de α
a,n a
α moyenne vectorielle de α , en degrés
v a
α moyenne scalaire de α , en degrés
s a

∆ module de la différence vectorielle entre la vitesse du flux laminaire de la soufflerie et la vitesse

mesurée pour une direction à l’azimut α , en mètres par seconde

∆ module de la différence vectorielle entre les vecteurs vent mesurés dans l’enceinte pour vent nul

a,b
avec l’instrument aux azimuts α et α , en mètres par seconde
a b
ème ème

∆ module de la différence vectorielle entre le n et m échantillon du vecteur vent mesuré dans

a,n,m
l’enceinte pour vent nul avec l’instrument à l’azimut α

ϕ inclinaison du capteur par rapport au flux d’air dans la soufflerie, en degrés; les angles positifs

correspondent aux axes du support au-dessus de l’horizontale, sous le vent, et les angles négatifs

correspondent aux axes du support au-dessous de l’horizontale
ρ masse volumique de l’air, en kilogrammes par mètre cube
Ω rotation de l’azimut de la vitesse angulaire du capteur, en degrés
5 Résumé des méthodes

Avant l’essai, il convient d’examiner le support de l’instrument afin de s’assurer qu’il est en parfait état et conforme

aux spécifications de conception du fabricant. L’exactitude de tous les mesurages et des résultats doit être vérifiée

et rapportée conformément à l’ISO 5725-1 et à l’ISO 5725-2.

 Essai en enceinte pour vent nul: le décalage de la vitesse du vent mesurée est déterminé sur la plage

opérationnelle de températures.

 Essai en soufflerie: l’écart de la vitesse mesurée par rapport à la vitesse vraie (vecteur) est déterminé sur les

plages opérationnelles de vitesses et de directions du flux.
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ISO 16622:2002(F)

 Essai en chambre de compression: détermination de la plage opérationnelle de masse volumique de l’air. Bien

que le principe de mesurage ne dépende pas de la masse volumique de l’air, une masse volumique minimale

est requise pour transmettre un son détectable.

 Essai sur le terrain: fournit la réponse à des conditions environnementales potentiellement défavorables, et qui

sont difficiles à simuler en laboratoire.
6 Examen du support avant les essais

S’assurer que le support est correctement orienté et aligné, qu’il n’est ni endommagé, ni obstrué.

Mesurer et enregistrer les longueurs de trajets entre les paires de transducteurs et les comparer aux longueurs de

trajets et tolérances spécifiées par le fabricant si celles-ci sont disponibles. Si les résultats excèdent les tolérances

du fabricant, mettre fin au mode opératoire.
7 Essai en enceinte pour vent nul
7.1 Objectif de l’essai

L'objectif de l’essai en enceinte par vent nul est de définir l’ampleur du décalage du zéro et/ou les problèmes

d’étalonnage ou d’alignement de l’instrument.

Le retard système (3.6) représente les temps de propagation du signal dans les transducteurs et le dispositif

électronique. La partie asymétrique du retard système (c'est-à-dire la différence des retards entre les deux sens de

propagation du signal) produit un décalage du zéro de la composante du vent correspondante. D’habitude,

l’exploitation du signal en direct, basé sur un étalonnage en usine, élimine largement le décalage du zéro.

Néanmoins, il est possible que le décalage varie avec le temps et la température. Cela peut être déterminé en

soumettant le support à l’essai dans une enceinte pour vent nul (voir annexe A).
7.2 Mode opératoire
7.2.1 Obtenir du fabricant les normes de performance en enceinte pour vent nul.

7.2.2 Placer le support dans l’enceinte pour vent nul et patienter jusqu’à ce que la température interne de

l’enceinte et le mouvement d’air soient stabilisés. S’assurer que l’anémomètre est en marche, mais que le

chauffage du support, s'il y en a, est éteint.

7.2.3 Régler l’intervalle d’intégration des valeurs du sonique à la même valeur que celle qui est utilisée pour

l’application. En cas d’utilisation d’un ventilateur dans l'enceinte, s’assurer qu’il est éteint.

7.2.4 Relever les valeurs affichées de température, de la vitesse et de la direction du vent ou des composantes

du vent mesurées par le sonique ⇒ U α ou ⇒ u v w et les enregistrer. L’indice a indique l’orientation de

a,n a,n a,n a,n a,n

l’azimut de l’instrument dans l’enceinte pour vent nul, et l’indice n indique le numéro de l’échantillon.

7.2.5 Répéter 7.2.4 au moins trois fois à 10 min d’intervalle. Si toutes les vitesses de vents mesurées sont

comprises dans le décalage du zéro spécifié de l’instrument, accepter. Indiquer la température de l’enceinte car le

décalage peut dépendre de la température. Si la conception de l’enceinte pour vent nul est approuvée par le

fabricant, mais si un échantillon ou plus des vitesses du vent mesurées excèdent le décalage du zéro spécifié de

l’instrument, rejeter.

7.2.6 Si la conception de l’enceinte pour vent nul utilisée n’est pas approuvée par le fabricant, et si un échantillon

ou plus des vitesses de vent mesurées excèdent les spécifications de l’instrument, s’assurer que la variabilité n’est

pas due à un mouvement d’air résiduel dans l’enceinte d’essai. À cet effet, calculer le module des différences

vectorielles.
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ISO 16622:2002(F)
∆=−(U sinα U sinα )+ (U cosα− U cosα ) (2)
a,n,m a,n a,n a,m a,m a,n a,n a,m a,m
ème ème

où ∆ est le module de la différence vectorielle entre le n et m échantillon du vecteur vent pour

a,n,m
l’instrument à l’azimut α.

Si la valeur maximale de ∆ est inférieure à 10 % de la spécification du décalage du zéro de l’instrument, le

a,n,m

décalage est stable avec le temps, et tout mouvement d’air peut être exclu. S’assurer alors que le décalage n’est

pas dû à la réverbération des parois. Pour ce faire, effectuer une rotation du support d’environ la moitié de son

angle de symétrie (60° pour un support dont l’angle de symétrie est de 120°) sur son axe d’azimut par rapport à

l’enceinte et patienter à nouveau jusqu’à ce que le mouvement d’air soit stabilisé. Relever une nouvelle fois les

valeurs affichées de la vitesse et de la direction du vent ⇒ U , α et les enregistrer.

b b

a) Sans réverbération des parois, le décalage du zéro est indépendant de l’orientation azimutale du support dans

l’enceinte d’essai (désignée par les indices a et b). Dans ce cas, le module de la différence vectorielle ∆ de

a,b

l'équation (3) est peu élevé [moins de 10 % de (U + U )/2]. Si tel est le cas, les décalages du zéro observés

a b
sont réels et non pas artificiels. Rejeter.
∆=−(U sinα U sinα )+ (U cosα− U cosα ) (3)
a,b a ab b a ab b

b) Dans le cas de réverbération des parois, le décalage du zéro spécifié de l’instrument dépend de l’orientation

du support dans l’enceinte et ∆ est élevé. Revoir la conception de l’enceinte d’essai pour vent nul.

a,b

Si la valeur maximale de ∆ [équation (2)] est élevée par rapport au décalage du zéro, soit le sonique est

a,n,m

instable, soit le mouvement d’air dans l’enceinte d’essai est trop important. S’assurer que l’équilibre thermique de

l’enceinte d’essai pour vent nul est constant.

7.2.7 Renouveler l’essai relatif au décalage du zéro aux limites supérieure et inférieure de la plage de

températures appliquée. Pour ce faire, une enceinte à température, qui s’adapte à l’enceinte d’essai pour vent nul

et au dispositif électronique du sonique est requise.

Essai à la limite de température inférieure: Le décalage du zéro ne dépend pas de la température de l’air, mais des

températures du transducteur et du dispositif électronique. Si le transducteur est équipé d’un système de

réchauffage, généralement activé à basse température, la température autorisée du transducteur peut être plus

élevée que la température ambiante minimale spécifiée. Étant donné qu’il convient d’éteindre le chauffage durant

l’essai pour vent nul, il est recommandé de régler la limite de température inférieure de la température de l’enceinte

à la plus basse température permise du transducteur.
8 Essai en soufflerie
8.1 Objectif de l’essai

L'objectif de l'essai en soufflerie est d'évaluer l’écart des mesures de vitesse de l’instrument par rapport à des

vitesses de flux connues en soufflerie.

Alors que la fonction de réponse idéale d’un sonique (pour une composante du vent) est donnée par l’équation

(B.2), la fonction de réponse vraie montre des écarts par rapport à cette équation. Ces écarts correspondent à un

décalage du zéro, décrit à l’article 7, et à des erreurs dues aux perturbations du flux et aux masques, qui peuvent

être déterminées quantitativement en comparant respectivement la direction et la vitesse du vent indiquées par le

sonique avec la vitesse du flux laminaire en soufflerie et l’orientation de l’azimut du sonique par rapport à l’axe de

la soufflerie. D’habitude, l’application de corrections pendant l’exploitation du signal en direct (voir annexe B)

permet de réduire les erreurs dues aux perturbations du flux et aux masques.

Les erreurs dépendent de la vitesse, de l’azimut et de l’angle d’inclinaison ϕ du flux. Par conséquent, un essai

complet exigerait un nombre très important de mesurages (de longue durée). Pour les besoins de l’essai

d’acceptation, un mode opératoire simplifié est décrit. Celui-ci tient compte du fait que les erreurs relatives

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ISO 16622:2002(F)

maximale et minimale se produisent toujours à peu près au même azimut et à la même inclinaison sur une large

gamme de vitesses de flux.

Les exigences minimales requises pour la soufflerie utilisée pour l’essai d’acceptation sont données à l’annexe C.

8.2 Précaution

Dans les souffleries à sections fermées, la réverbération des parois peut être à l’origine d’erreurs (voir également

l'article 7). L'objectif du mode opératoire qui suit est de déterminer quantitativement cette erreur due à la

réverbération. Avant de procéder à ce mode opératoire, l’essai en enceinte pour vent nul doit avoir été concluant.

Ce mode opératoire dépend de la vitesse la plus basse possible dans la soufflerie (mouvement résiduel, si la

soufflerie est fermée).

a) La vitesse de la soufflerie peut être réglée à des valeurs inférieures au décalage du zéro spécifié pour

l’instrument.

1) Relever et enregistrer les valeurs affichées de la vitesse du vent mesurée U pour cinq angles de l’azimut

d’orientation α du sonique dont les valeurs sont comprises dans les limites de la moitié de l’angle de

symétrie du support (par exemple α = 0°, α = 15°, α = 30°, α = 45°, α = 60° pour un angle de

1 2 3 4 5
symétrie du support de 120°).

2) Si toutes les valeurs de U sont égales ou inférieures au décalage autorisé, les erreurs par réverbération

peuvent être exclues.

b) La vitesse de la soufflerie ne peut pas être réglée à des valeurs inférieures au décalage du zéro spécifié pour

l’instrument.

1) Régler la vitesse du vent dans la soufflerie U à la valeur la plus basse possible, avec une direction et une

vitesse correctement définies.

2) Enregistrer la vitesse du vent mesurée ainsi que sa direction (U , α ) pour cinq angles de l’azimut

a a

d’orientation α du sonique dont les valeurs sont comprises dans les limites de la moitié de l’angle de

symétrie du support.

3) Calculer le module de la différence vectorielle à la vitesse du flux laminaire dans la soufflerie.

∆=−(sU inα Usinα)
...

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