FATE OF MERCURY IN THE ARCTIC Michael Evan ... - COGCI

Fate of Mercury in the Arctic 41
3. A data acquisition suitcase. The central component of the suitcase is an Advantech 4823
single board computer, with a PC 104 bus. There is a relay card mounted on the bus to
control switching valves and a 12 bit analogue input card for monitoring up to 6
analogue input signals plus the supply voltage and an analogue zero channel. A RS422
serial port on the Advantech computer allows serial data input from the sonic
anemometer. A 3 ½ inch floppy disc drive is provided for data download and back-up.
Automatic data back up is a function of the software. A 6 GB hard disk with a DOS
operating system controls the REA data acquisition software, DAQ,
METSUPPORT/Risø DAQ version 4.10, with integrated REA control. The initial
software set up provides for automatic booting once power is supplied to the system. A
60-minute run, made up of two minute archived statistical data blocks will start at either
clock time 00 or clock time 30, unless manually bypassed. The REA control software
has a deadband, based on a moving 10-minute standard deviation of the sonic vertical
signal and an adaptive correction for tilt angle. The average tilt angle is calculated for
every four-degree sector and the vertical component of the wind is corrected using this
angle. The software used only the most recent 10 minutes to determine the average tilt
angle, to best account for changes in flow regimes due to varying speed and stability.
Therefore, the REA system will first start switching 10 minutes after it is started. The
above software is designed to maximize the REA measurements. The deadband is
discussed later in this thesis. The software output was written to write just basic data to
the floppy drive at the end of each hour, i.e. run. This data includes those factors needed
to calculate the flux and control the measurement including: run name, defined
conveniently as the date and start time, average temperature for the run, average wind
speed for the run, average wind direction for the run, the standard deviation of the