Wind

• Ultrasonic Anemometer 2D
• Ultrasonic Anemometer 3D

Ultrasonic Anemometer 3D

The 3D Ultrasonic Anemometer (USA-1) is an all weather type system which has proven reliable operation in arctic and Antarctic areas, in highly polluted areas of waste disposals, at mountains, at coastal sites, on ships, etc.

On the other hand, this system is capable to measure very low flow velocities, starting with lowest value 2 cm/s. You will get with one sensor the direction and speed or the three components of the air-flow. Additionally you will get accurate values for the fluctuations of the virtual temperature. That makes it very easy to derive turbulent parameters like heat flux.

The optimal design with three outer paths of measurement around a middle bar is ideal to minimize flow distortions. The sensor head is of V4A stainless steel. No moving parts are necessary for a highly accurate measurement. Therefore the sensor can detect wind speeds without threshold near 0 m/s. USA-1 has a embedded self-check algorithm which validates the system performance and outputs on-line measures for the signal quality.

Due to the principle of measurement no calibration during long term unattended operation is necessary. No bearings are subject to wear and tear and no frequently sensor maintenance will be important for a proper system operation. A factory zero wind system check will be done to fix the system parameters. Later zero wind calibrations will only be necessary in case of mishandling of the sensor and can usually be done on the user site.

Both system types (USA-1 “Basic” and USA-1”Scientific”) can be equipped with sensor head heating 55 Watt or extended 100 Watt for extreme weather conditions.

USA-1 will provide the data automatically on a serial interface RS232 or RS422. This provides an easy opportunity to connect the USA-1 with a computer or Combilog.  Small programs (e.g. Hyper-Terminal on WINDOWS-systems) which read the incoming data from the interface will be sufficient to get the data on the computer. No special protocols for the data exchange will be needed. The interface program tcopy is available in the internet and will be part of the delivery. For the data set, please refer to the following sections.

It is recommended to use the RS422 interface for a data transfer distance more than 20 m.

Optional available are also an analogue output of the parameters x, y, z and T(v) (-or- velocity, direction, z-component and virtual temperature)  for the connection to analogue logging devices.

We will introduce to you with this quotation two different versions of sensors. USA-1 “Basic” is the already known sensor for wind and turbulence measurement for a variety of applications. USA-1 “Scientific” is the improved version with a new processor and several new features. Please refer to the configuration matrix about the available extensions for the sensor.

USA-1 “Basic”

The USA-1 “Basic” is  the ultrasonic anemometer for a wide variety of applications. It provides a selectable 2-dimensional flow correction with a digital data output RS232 or RS422 (to be specified with order). Optional the system can be extended with sensor head heating and analogue output channels. The maximum sample rate is specified with 25 Hz for average data.

The data output in ASCII-format occurs as follows:

(data set of the USA-1”basic”)

 

     M:x =     2 y =     4 z =    -8 t =  2245

     M:x =     1 y =     4 z =    -7 t =  2242 

Or wind speed, wind direction, z-component and virtual temperature with fixed field size

     M:v =     4 d =   326 z =    -6 t =  2201

     M:v =     4 d =   304 z =    -6 t =  2202

The letter M in front of the row indicates the measurement. This letter will change to H in case the heating is in operation. The E will occur in front of an error-message.

 USA-1 „Scientific“

The USA-1 „scientific“ is a powerful improved version for applications where comprehensive measurements are required. Especially the connection to additional sensors (e.g. Eddy-Flux-stations) are a strong point of this sensor type. Even data output delays from external sensors can be taken in account on user command.

The basic sensor USA-1 “scientific” already provides an internal memory chip and a battery buffered clock. The memory unit can store approximately store approx.12300 data sets of standard data rows – rawdata or average data  without turbulence option- and  approx. 2700 sets for the data from the turbulence option

The user can choose between the already known 2-dimensionsl flow correction and a new 3-dimensional head correction. The sampling rate depends on the chosen head correction;

40 Hz for the 3-dimensional and 50 Hz for the 2-dimensional. The head correction can also  be switched off by the user.

Optional available analogue input channels provide the possibility to link external sensors (e.g. humidity, pressure etc) to the USA-1. The data of these sensors will be recorded synchronously to the wind measurement and implemented into the data set.

Especially for numerical modeling of dispersion processes, turbulent parameters are essential. The optional available turbulence option calculates online the values of for example monin-obukhov length, fluxes etc. The user of the system can choose between the data output of only-turbulence data set, a  mix of turbulence data set and raw-data or only raw data by user command.

Following an example of the output data set is shown for the online turbulence calculation routine. Please refer to the data set of the USA-1 ”basic” for the output data set without turbulence option.

The first row of the data set shows a header with data/time indication, average time, sample rate and SONIC DATA QUALITY (number of valid measurements within the sampling interval in percent).

• Technical Specification
• Variations

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