Campbell Scientific AP200 CO2/H2O Atmospheric Profile System - Manual (Page 26)

AP200 CO
2
/H
2
O Atmospheric Profile System
65
70
75
80
85
90
95
100
105
0 500 1000 1500 2000 2500 3000
Elevation (m)
Am
bi
en
t P
ressu
re (
kP
a)
FIGURE 4-19. Nominal ambient pressure as related to increasing
elevation
FIGURE 4-20 shows the nominal sample flow as a function of ambient
pressure, assuming a 35-kPa pressure drop across the orifice.
180
190
200
210
220
230
240
250
70 75 80 85 90 95 100
Ambient Pressure (kPa)
Sa
m
ple
F
lo
w
(m
l/m
in
)
FIGURE 4-20. Nominal sample flow rate as related to increasing
ambient pressure
Taken together, these two graphs show that the nominal flow varies from 247
ml/min at sea level to 180 ml/min at 3000 m. The flow rate is reported in
public variable sample_flow. Some variation in flow (approximately 10%) is
to be expected due to variation in the actual size of the orifices and in the
calibration of the flow sensor. For example, at an elevation of 1000 m, the
nominal ambient pressure is 90 kPa, which gives a nominal flow of 225
ml/min. The normal expected range for the flow would be from ~200 to ~250
ml/min.
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