TRAINING OF WIND SPEED CALIBRATION

REPUBLIC OF TURKEY MINISTRY OF ENVIRONMENT AND 

FORESTRY, TURKISH STATE METEOROLOGICAL SERVICE, 

CALIBRATION CENTER 

TRAINING OF 

WIND SPEED CALIBRATION 

Zafer Turgay DAĞ 

Quality Manager / 

Chief of wind speed calibration laboratory 

September 2011 

Turkish State Meteorological Service 

Ankara/Turkey 

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Headlines 

•Introduction of Wind Speed Calibration Laboratory 

•Types of wind tunnel 

•Air flow measurement 

•Systems and principles of wind speed measurement 

•Basics of Uncertainty 

•Calibration Certificate 

•Flow profile, Homogeneity test, Immersion depth and 

Turbulance effect 

•Appreciate the WMO standards for wind measurements 

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Introduction of Wind 

Speed Calibration Laboratory 

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Wind Speed Calibration 

Laboratory 

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Laboratory 

Wind Speed sensor types to be calibrated (Cup, hotwire, 

ultrasonic, pitot, vane, propeller anemometer): 

1.Electronics wind speed sensors, 

2.Mechanical wind speed sensors. 

Calibration Center - Ankara 2010 

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Quantity, 

Instrument to be 

calibrated 

WIND SPEED SENSORS 

(REFERENCE IS 

ULTRASONICS) 

WIND SPEED SENSORS 

(REFERENCE IS PITOT 

TUBE 

MICROMANOMETER) 

Scope of Accreditation 

Measuremen 

t Range 

0,5 m/s - 35 m/s 

0,5 m/s - 35 m/s 

Measuremen 

t Conditions 

With Ultrasonic 

Anemometer 

With Pitot tube+ 

Micromanometer 


Best 

Measuremen 

t Capability 

(k=2) (±) 

±(0,1+%0,01xV) 

m/s 

± (0,05 + 

%0,005xV) m/s 

Remarks 

COMPARISON 

METHOD 

COMPARISON 

METHOD 

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Furness Control FCO510 

Micromanometer and Pitot tube. 

Reference devices 


Thies 2D Ultrasonic Anemometer 

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Laboratory 

Wind Speed Tunnel is the Göttinger type, closed 

loop and open test area ( 0 – 40 m/s ). 


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Devices of the Wind Speed 

Calibration Laboratory 

Hotwire Testo 435 

Wind Speed Sensor 

Druck PTX7517-1 Pressure Sensor 

PR 5333A Temperature (0-40ºC) sensor 


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Devices of the Wind Speed 

Calibration Laboratory 

Vaisala WMS302M and WAA151, Thies Clima 

4.3303.22.007, Qualimetrics ECN4738, Siap 

handel type, Vector İnst. A100M/HE-1 and Lastem 

DN002 Wind Speed sensors are used. 


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Parts of wind tunnel 

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Main Construction of Wind Tunnel 

1-Bell Mouth 

Uniform flow 

It prevents loss of suction 

2-Honeycomb 

Decreases to swirl effect 

Decreases to turbulance effect 

3-Screen 

Total pressure balance by reducing the velocity distribution 

Make hydrodynamic resistance 

4-Contraction 

Provides a uniform flow rate by increasing the wind speed 

5-Test Area 

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Open Jet Closed Jet 

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Honeycomb Intake Screen and Bell-mouth contraction 

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Air flow measurement 

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Air Flow Measurement 

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Systems and principles of some 

wind speed measurement 

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Schematic display of LDA 

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Laser Doppler Anemometer (LDA) 

•The best for all wind speed range 

•Non-intrusive measurements (optical technique) 

•Very low uncertainty 

•Very high spatial resolution due to small measurement volume 

•Very low turbulance 

•Not effect environmental conditions 

•Don’t need calibrate or ziro drift 

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Pitot-static tube 

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How it works: 

Measure pressure differential in two different locations 

•Pitot tubes are still routinely used for flow Measurements 

•Based on differential pressure measurement 

•Provide the reference for flow measurement 

•Two general types 

– L type (also the ellipsoidal tipped E-Type) 

– S type 


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– A pair of concentric tubes 


– Stagnation port is a blunt obstacle to airflow (drag 

coefficient is unity) 

– Static port is located at a point far enough back along the 

tube to have no dynamic flow effects at all 

– Must be oriented into the airflow 

– Ideal for wind tunnels (reliable and cheap) 

– Usually it requires a controlled environment for operation 

– Not good at under 1 m/s, designed to measure very high 

wind speeds 

– Choising manometer is very important 

– It must be keep upright and maximal inclination must be 5 

degree 

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S type pitot tubes 

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Differential Pressure Equation 

•P1 is a flow line, brought to a halt at P2 

•Conservation of energy between point P1 and P2 

•We actually measure the differential pressure Δp between P1 

and P3, taking P3 to be representative of P1 

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Hot-wire and hot-film anemometers 

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Hot-wire and hot-film anemometers 

How it works: 

Exposed wire carrying current is adjusted to maintain constant 

wire temperature 

•Susceptible to drift 

•Good at under 5 m/s, but bad at up 5 m/s 

•Sensitive for up to 20 m/s (breakdown is possible) 

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How it works: 

Sonic anemometers 

Measures the time required to transmit an acoustic signal 

across a fixed path to determine the wind velocity 

component along that path 

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Sonic anemometers 

– Much better resolution than cup and propeller 

anemometers 

– Can measure very low wind speeds 

– More accurate 

– Good resolution 

– Requires considerable power 

– Greater bandwidth than mechanical 

anemometers but less than hot-wire or hot-film 

anemometers 

– Sensitive for transportation/take down/mount 

(sensor arms are very important) 

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Basics of uncertainty 

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Source of Uncertainties 

• Uncertainty of reference sensor 

• Annual drift of reference sensor 

• Uncertainty of Environmental effects 

(temperature,humidity,pressure) 

• Uncertainty of reference sensor resolution 

• Uncertainty of test sensor resolution 

• Uncertainty of mistake repeatability 

• Uncertainty of homogeneity 

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• Uncertainty of blockage effect 

• Uncertainty of turbulence effect 

• Uncertainty of swirl effect 

• Power requirements 

• Inadequate educated person 

• Source of any other winds especially heatings, blowers, 

air conditioners etc… 

• Opened doors or windows 

• Carriage, transportation 

• Vibrations etc…. 

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• We can measure, control and to zero some of uncertainty 

sources but some of them can’t go to zero level and can’t 

calculate. It depends on laboratories, calibration 

procedures, reference sensors, environmental conditions 

and experiments. There are a lot of detail about 

uncertainties. 

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Evaluation of standard uncertainty … 

•Type A 

repeated measurements 

statistical evaluation 


•Type B 

information about previous measurement data 

manufacturer´s specification 

data provided in calibration certificates 

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Type A 


•minimum of 10 measured data 

•evaluation of the arithmetic mean 

•evaluation of the root mean square deviation … 

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Vurgulanması istenen noktalar için italik, alt çizgili, farklı 

renk, yanıp sönme gibi özellikler kullanılmalıdır. 

Kullanılan resim ve grafikler 

dikkatlice seçilmeli, sade ve 

anlaşılır olmalıdır. 

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Calibration Certificate 

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The calibration certificate 

Contents: 

-page 1- 

•the object 

•the manufacturer 

•the type 

•the serial number 

•the customer 

•the order number 

•the number of pages 

•the date of the calibration 

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-page 1- 

following information is represented in the calibration mark 

•consecutive number of the calibration certificate Example: 2010-10 0998 

•the identification number of the laboratory Example: AB-0072-K 

•the year and the month Example: 2010-10 

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-page 2- 

the following components are represented 

•the reference sensor 

•the object of calibration 

•the method of calibration 

•the ambient conditions and 

•Calibration results 

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Flow profile 

Homogeneity test 

Immersion depth 

Turbulance effect 

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Searching flow profile 

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Finding flow profile 

The flow profile at 10 m/s 

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An example of homogeneity test 

63 different test points and all wind speed range 

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The influence of immersion depth 

• If you place a vane anemometer in a wind tunnel the test bed 

resistance raises and the volume flow decreases. 

Therefore: The anemometer should indicate a lower value. 

• However the deeper the anemometer is in the air flow, the 

higher is the value displayed. 

So, what happens? 

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• During the calibration the anemometer is placed in the 

measurement section. Vane anemometer and a part of the 

pole extend into the cross section of the nozzle. 

• The air flows through the vane and around the pole, not only 

radial around the pole but also axial. 

• The axial air flow leads to the head of the anemometer and 

accelerates the vane. The display indicates the value + the 

value of the influence of the pole. 

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immersion depth:50 mm from the fringe 

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The influence is dependent on: 

• The geometry of the anemometer 

• The body structure of the pole 

• The nozzle cross section 

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The blockage effect 

• This effect is influenced by the immersion depth and the 

size of the anemometer. 

• Basically: the bigger the head and the pole of an 

anemometer is the higher is the blockage effect in the 

flow field. 

• This effect influences the wind tunnel as well as the 

calibration 

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What happens inside the wind tunnel? 

• The pressure accumulates against the flow direction. 

An influence on the result of the reference is possible. 

• The test bed resistance in the wind tunnel raises up and the 

volume flow decreases. 

• In a closed measuring section the air velocity raises around 

the probe. The value at the display increases. 

• In an open measuring section the air flow enlarges around 

the probe. The value at the display decreases. 

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A sample of simulation 

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Placement of reference/test sensor 

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Placement of reference/test sensor 

Reference and test sensors should not be aligned 

Tip of the pitot tube must be far from the outlet of 

wind tunnel 

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Appreciate the WMO standards 

for wind measurements 

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WMO commendation 

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WMO commendation 

Required measurement uncertainty 

means calibration laboratory results. 

Achievable measurement uncertainty 

means field calibration/on site calibration 

results. 

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The End 

Thanks for paying attention! 

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TRAINING OF WIND SPEED CALIBRATION

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