3.3. UVP monitor and ActiveX libraries
In this work the latest UVP instrument (UVP-DUO-MX, Met-Flow SA, Lausanne, Switzerland) was used for velocity profile measurements. A more detailed description, as well as technical information about the UVP instrument, can be found in Met-Flow SA [17].
The communication with the UVP instrument works via a TCP/IP protocol over an ethernet connection. There are two options to interact with the instrument. One is the software included from the manufacturer which provides a GUI to set the UVP parameters and record the velocity profiles. Statistical analysis tools are also available in the software and data can be exported in text files for further processing. An alternative way is the ActiveX library from Met-Flow which allows a modified firmware in combination with third party software application to communicate with the UVP-DUO and to have direct access to the DMEA data for each pulse emission, which is not available in the commercial software. The new UVP approach using modified firmware in combination with ActiveX library (‘UVPAX’) and access to DMEA data for each pulse emission was developed and improved considerably by Wiklund [33] and Birkhofer [34]. This made it possible to use a Matlab® based application to set parameters, record profiles calculated on the instrument’s Digital Signal Processor (DSP) and implement alternative velocity estimation algorithms using DMEA data, which was not previously possible. Furthermore, direct access to DMEA data or ‘raw data’ allows increased control of signal quality and gain amplification levels, detection of signal artefacts as well as correction of aliasing phenomena, as shown by Wiklund [33].