OMC-042 / 043 / 044 Data loggers
Users
’ manual
page 40
Aggregation Channels
The logger is equipped with 8 aggregation channels which can be used to record aggregated values
(average, minimum, maximum, gust and standard deviation) calculated over a period of your choosing.
The number of samples taken into account during the aggregation period is depending on the period
duration and the
‘Sample interval’ as configured for the used input parameter/sensor.
Each channel has an aggregation buffer of 600 values. So a 10 minute aggregation period (600 seconds)
can be sampled with 1Hz, longer aggregation periods e.g. 20 minutes can be sampled with 1Hz but will
effectively be sampled every 2 seconds. As 1Hz is the highest possible aggregation sample rate, shorter
aggregation periods will contain less samples (e.g. 120 samples for a 2 minute aggregation interval). An
aggregation interval can be shorter or longer than a data log interval, so it’s possible to record a 10
minute (rolling) average every 2 minutes. Or record the last 2 minute average every 10 minutes.
With a 1Hz sample rate the logger needs to wake-up and take a sample every second, to avoid draining
the batteries the used sensors should require a short warm-up (a fraction of the sample interval) consume
as little power as possible preferable none (like a reed switch based anemometer), self-powered (like a
pyranometer) or negligible (like a 20KOhm wind vane potentiometer). The power draw is about reversed
proportional to the sample interval, a twice longer interval will draw about 50% less power.
Per aggregation channel you have to choose
which input/sensor values you want to use for
aggregation.
Choose an aggregation period, a commonly
used wind speed aggregation period is 10
minutes.
As wind direction is a vector, please switch
‘Vector Aggregation’ to ‘On’, this will split up
the samples in to an x and y components and
combine them back to an aggregated vector.
E.g. a northern wind flapping between 340 and 10 degrees will result in an average northern wind of 355
instead of a faulty 175 degrees southern wind.
Configuration setup
[0] Exit
[1] General settings >> OBS6721BK
[2] Modem settings
[3] NTP time update >> Used
[4] Alarm SMS >> Not used
[5] SMS commands >> Not used
[6] Internal sensors >> Internal
[7] Analog sensors >> Potmeter
[8] Digital sensors >> Digital pulse
[9] Network signal sensor >> Not used
[A] Serial port >> Not used
[B] Accessory port >> Not used
[C] Derived channels >> Used
[D] DTU connection >> Not used
[E] Email output >> Not used
[F] FTP output >> Not used
[G] TCP output >> TCP
[-] HTTP output >> N/A
>
Derived channels
[0] Exit
[1] Aggregations >> Used
[2] Calculations >> Not used
Aggregation channel 1
[0] Exit
[1] Input parameter >>
Direction (D)
[2] Aggregation period >>
00:10:00
[3] Vector aggregation >>
On
[4] Average >>
Average Direction
[5] Minimum >>
Minimum Direction
[6] Maximum >>
Maximum Direction
[7] Gust >> Not used
[8] Deviation >>
Deviation
Direction
[R] Remove
>
