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Ultrasonic Wind Sensors & Your Wind Measurement Campaigns

Ultrasonic Wind Sensors & Your Wind Measurement Campaigns
Overview of ultrasonic wind sensor technology, as well as results from wind tunnel and field tests. You will also learn ways to get the most value from your wind measurement campaigns.

​​​This webinar provides an overview of ultrasonic wind sensor technology, as well as results from wind tunnel and field tests. You will also learn ways to get the most value from your wind measurement campaigns.

Questions & Answers

Q: What is the heating voltage for the heating element?
A: The heating voltage varies depending on the manufacturer and design of the ultrasonic wind sensor. The Vaisala WMT700 ultrasonic wind sensor recommended voltage is 24 VDC but it can range from 12-40 VDC where 40 VDC is the absolute maximum. The Vaisala WMT700 heating power ranges from 30W for the transducers to up to 350W for full body, sensor arm and transducer heating which will be commercially available later this year. Stand-alone power supply systems are typically needed for met towers with heated mechanical anemometers or ultrasonics due to the aforementioned requirements.

Q:
 As far as calibration, can you do more than a zero calibration on the field?
A: It is impossible to recreate wind tunnel conditions in the field to do a calibration. You can use the Vaisala WM Verifier to test the mechanical integrity and perform one-point checks in the field for the Vaisala WMT700 ultrasonic wind sensor. Vaisala recommends that you calibrate your ultrasonic wind sensors every 24 months.

Q: How do you calibrate the ultrasonic sensor on site?

A: The Vaisala WM Verifier is a field usable calibration verifier for use the WMT700 ultrasonic wind sensor. It is a small echo-free chamber for testing the mechanical integrity of the WMT700 and performing one-point field checks. The verifier ensures that the array is undamaged and transducers are parallel to each other. The WMT700 must read less than 0.22 m/s with the verifier in place to be properly calibrated.

Q: What is the model or p/n for the calibration of ultrasonic wind sensor?

A: The field calibration apparatus for the Vaisala WMT700 is known as the WM Verifier.

Q: What is the recommended calibration procedure for an ultrasonic in a wind tunnel? One wind speed, one orientation or would you rotate through 180 degrees?

A: Vaisala has developed a calibration process with the MEASNET wind calibration laboratories that evaluates sensor performance at a range of wind speeds between 4-16 m/s at 0 degree orientation as is done with mechanical anemometers with the results sharing the ultrasonic wind sensor's slope, offset, standard error and correlation coefficient to the traceable wind tunnel speeds and direction.

Q: How about the alignment tool for the ultrasonic sensors?

A: The Vaisala WM Verifier can be used to ensure the integrity of the Vaisala WMT700 structure and alignment. Ultrasonic wind sensors always have a true north indicator that should be aligned using a compass during installation.

Q: Is there any work being done to get the Ultrasonic sensors certified like the mechanical ones? Also, what are the reasons that ultrasonic sensors currently aren't certified?

A: Yes, there is a committee creating a revision to the current IEC 61400-12-1 standard that will accommodate the use of ultrasonic wind sensors and remote sensing. Vaisala is participating as an industry observer through the Finland representative, VTT.

Q: Would you recommend installing the ultrasonic device pointing upwards or downwards?

A: The installation orientation of the ultrasonic wind sensor is at the discretion of the customer. The performance of the sensor is the same in either installation method.

Q: Does the new IEC version include sodar measurement as well?

A: Yes, the revision to the IEC 61400-12-1 is expected to provide guidance for best practices using SODAR and LIDAR remote sensing measurements as complementary measurements to met towers.

Q: Do you see that in, eg. a 120 m meteorological mast, a 2 D ultrasonic device could replace one traditional wind vane (if 2 wind vanes are planned to be used) or even all of them so that the wind direction data would be received only from the ultrasonic?

A: Yes, guidance for wind direction measurements using ultrasonic wind sensors is also expected in the revision to the IEC 61400-12-1 standard. The combined wind speed and direction measurement of an ultrasonic wind sensor is an advantage and can limit the amount of sensors and booms required in a met tower design. Naturally, you should consult with GL-GH to understand their preference in advance of release of the IEC 61400-12-1 revision.

Q: How do icing effects manifest in unheated ultrasonic wind data?

A: Ice and snow will typically build-up on the sensor body and along the sensor arms and transducers. When the transmission of the ultrasonic signal between the transducers is compromised, error messages will be sent by the sensor and no measurements will be collected. Vaisala recommends Dr. Shigeo Kimura and his independent ice tunnel research for more information on this subject.

Q: Do ultrasonic sensors get damaged by dust particles?

A: Ultrasonic wind sensors are manufactured out of stainless steel, so they are more resilient to ambient environmental conditions than their mechanical counterparts. In very dusty environments, regular preventative maintenance is recommended to ensure the transducer heads stay clean and measurement quality is not compromised.

Q: How much experience do ultrasonics have offshore and have they been proven reliable offshore?  Any maintenance issues offshore that you have been aware off?

A: Ultrasonic wind sensors have been used for over 15 years in offshore applications, such as offshore oil & gas platforms, helidecks and coastal meteorology observation stations. Proper care should be taken to ensure that connectors and sensor holders are not designed from materials that will corrode, but the stainless steel structure of most ultrasonic wind sensors is well designed for offshore conditions.

Q: What is the corrective action if the sensor is not responding?

A: Most ultrasonic wind sensors provide two-way communication, so self diagnostic tests can be conducted remotely to troubleshoot problems and determine if a site visit is required.

Q: What should be the min distance from any building or obstruction to the sensor?

A: The IEC 61400-12-1 standard describes how wind sensors should be installed to minimize disturbances in wind energy applications.

Q: What is the price comparison of mechanical versus ultrasonic?

A: There are a wide range of commercial providers for both mechanical and ultrasonic wind sensors with differing performance and heating specifications. 2D ultrasonic wind sensors are typically 2-3 times more expensive than mechanical anemometers, but the wind direction measurement is included and lifecycle costs of operation are lower. 3D ultrasonics can be up to 10 times more expensive due to their unique physical structure and lower sales volumes.

Q: Can ultrasonic sensors effectively double as temp sensors?

A: Due to heating of the sensor, most ultrasonic wind sensors cannot directly measure temperature, however combining the time of flight of the ultrasonic signal between transducers with humidity can calculate virtual temperature. This is the temperature of the air if all moisture were removed without changing its pressure and density, so this is not directly applicable to most meteorological applications. If temperature and wind speed and direction measurements are required, Vaisala offers the WXT520 Weather Transmitter.
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​The speaker in this recording is Mr. Nicholas Wilson, Meteorologist and Regional Market Segment Manager for Wind Energy, Vaisala.

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