Campbell CPEC300, Руководство по эксплуатации продукта, Страница: 96 / 175

CPEC300/306/310 Closed-Path Eddy-Covariance Systems
87
If the CPEC310 system enclosure is a long distance from the
EC155 gas analyzer (e.g., tall tower installation), it may be
necessary to increase the value of the constant TIME_ZRO_SPN
(see Section 6.2 , Set Constants
(p. 36)
) to allow for more
equilibration time, especially for H
2
O. If the tubing is so long that
it becomes impractical to wait for equilibration, the dewpoint
generator may be taken up the tower and connected via a short
length of tubing to the Zero/Span port on the back of the EC155.
If this type manual setup for doing an H
2
O span is used, it may be
easier to take a laptop PC up the tower and use
ECMon
software
to do the H
2
O span. See the EC155 user manual for details on
doing a span using ECMon .
7.2 User-Initiated Manual Zero/Span for CPEC300 or CPEC306
Neither the CPEC300 nor the CPEC306 contains a valve module, therefore,
these systems require the user to manually connect and flow a zero or span gas
through the gas analyzer. The tubing carrying the zero or span gas should be
connected to the port labeled
Zero/Span
on the back of the EC155 gas
analyzer head, and the zero or span gas flow should be set using a flow
regulator as described in the EC155 user manual. Once plumbing connections
are prepared, the following sections may be followed to set the zero, CO
2
span,
or H
2
O span.
When doing manual zero and/or spans, track the drift of the
analyzer. This requires the user to first check the CO
2
and/or H
2
O
readings against their span gas concentrations and against the zero
gas before setting either the zero or span. Refer to the EC155 user
manual for more information on tracking the analyzer gain and
offset.
If errors in setting up and performing a zero or span lead to
nonsensical measurements or a despondent state of the analyzer,
the analyzer’s CO
2
and H
2
O coefficients may be restored to
previous values by navigating to Zero Span Coeffs under the
Initial Configuratn menu. Once in this menu, highlight
Reset/Change Coeffs and press Enter . To change a coefficient,
highlight it, press Enter , type the desired value, and press Enter
again to save the value. If the previous coefficient value is
unknown, enter 1.00, which will restore it to its factory settings.
After entering values, scroll to Reset Coeffs , press Enter ,
highlight TRUE , and press Enter. The analyzer is now reset, and
a proper zero/span may be attempted again.
7.2.1 CPEC300/CPEC306 Manual Zero
If zeroing the analyzer, use the CR1000KD keypad to navigate to the
Attendant Zero/Span menu and then to the Prfrm Field Zero menu. Scroll
down and highlight Pump Off , press Enter , highlight TRUE , and press Enter .
The pump is now turned off. Make sure the zero gas tubing is connected to the
Zero/Span
port on the back of the EC155 gas analyzer head and allow zero gas
to flow. If needed, use higher flows (> 1 L/min) initially to flush out the sample
NOTE
NOTE
NOTE