Campbell Scientific EC150 CO2 and H2O Open-Path Gas Analyzer and EC100 Electronics with Optional CSAT3A 3D Sonic Anemometer - Manual (Page 50)

Appendix A. EC150 Settings
A.2.1 SDM Address
This parameter must be set to use SDM output from the EC100. See Section
4.6.2.1, SDM Output, for details on using SDM output.
Each SDM device on the SDM bus must have a unique address. The EC150
has a factory default SDM address of 1, but may be changed to any integer
value between 0 and 14. The value 15 is reserved as an SDM group trigger.
The SDM address is stored in non-volatile memory of the EC100 electronics.
A.2.2 Bandwidth
The EC100 has a user-selectable, low-pass filter to select the bandwidth (5, 10,
12.5, 20, or 25 Hz). Setting the bandwidth to a lower value will reduce noise.
However, it must be set high enough to retain the high-frequency fluctuations
in CO
2
and H
2
O, or the high frequency contributions to the flux will be lost.
The factory default bandwidth is set to 20 Hz which is sufficient for most flux
applications. Lower bandwidth settings may be used for higher measurement
heights which inherently have lower frequency content. Refer to Appendix B,
Filter Bandwidth and Time Delay, for more information on the digital filter
options.
If a spectral analysis is performed to evaluate the experimental setup, the
bandwidth should be set to the Nyquist frequency, which is half the datalogger
sample rate (for SDM output) or half the unprompted output rate (for USB and
RS-485 output). This ensures that the data will not be under-sampled and that
higher frequency variations will not be aliased to lower frequencies.
If too small a bandwidth is selected, high frequency fluxes will be
filtered.
The Bandwidth setting is stored in non-volatile memory of the EC100
electronics.
A.2.3 Unprompted Output
If the EC100 is to output data in one of the unprompted modes (USB or RS-
485, see Appendix C.1, USB or RS-485 Output), this setting must be set
accordingly. The factory default is to disable the unprompted output, assuming
data will be logged via SDM (see Section 4.6.2.1, SDM Output).
Only one unprompted output type (for example, USB or RS-485) may be
selected at a given time. The rate at which the EC100 outputs these data is
determined by the Unprompted Output Rate setting.
The Unprompted Output Rate setting is stored in non-volatile memory of the
EC100 electronics.
A.2.4 Unprompted Output Rate
When the Unprompted output is enabled, this setting determines the output rate
for unprompted output (USB or RS-485, see Appendix C.1, USB or RS-485
Output). If the unprompted output is disabled, this parameter is not used. The
factory default output rate is 10 Hz, but it may be set to 10, 25, or 50 Hz.
NOTE
A-2