Campbell Scientific CPEC200 Closed-Path Eddy-Covariance System - Manual (Page 99)

Appendix G. CPEC200 Scrub Module
Installation, Operation and Maintenance
The CPEC200 Scrub Module provides a stream of air that has been scrubbed of
CO
2
and H
2
O and is used for zeroing the EC155. The module is housed in a
fiberglass enclosure that can generally be mounted to the same structure as the
CPEC200 system enclosure. The enclosure is shown in FIGURE G-1, and the
specifications can be found in Appendix G.2, Scrub Module Specifications.
FIGURE G-1. CPEC200 scrub module
G.1 Theory of Operation
The CPEC200 Scrub Module provides an air stream with CO
2
and H
2
O
removed to zero the EC155. It includes a small diaphragm pump to push the
zero air to the analyzer and three bottles containing a molecular sieve to
remove CO
2
and water vapor from ambient air. The pump provides
approximately 1.5 LPM flow. It has a heater and fan to keep it within its
operating range (5ºC to 50ºC) over ambient temperatures down to –30ºC. The
CPEC200 scrub module is intended to replace the cylinder of compressed zero
air. The optional valve module for automated zero is also required if using the
scrub module.
The CPEC200 scrub module pump pulls ambient air through three bottles of
molecular sieve and pushes it to the valve module. The ambient air inlet and
zero air outlet fittings are on the bottom of the enclosure. It uses a small
diaphragm pump that is mounted in an insulated, temperature-controlled box
inside the weather-tight fiberglass enclosure.
The following are description of the operating parameters of the scrub pump.
G-1