Owner's manual

6.2 Flow Rate and Tubing Size
It is important to maintain the high frequency response for eddy covariance measurements. The frequency response of
the analyzer itself is discussed in section 1.7.1. The other consideration is to avoid the loss of high frequencies by
mixing in the tubing from the air sample intake to the analyzer. Using a high flow rate and a minimum length, small
diameter sample tube will help to preserve the high frequency variations in the trace gas concentration. Normally the
analyzer is placed at the base of the mast to minimize the tube length, and smallest diameter that will allow the desired
flow rate is used. through show predicted pressure drops and travel times for selected tubing
diameters and flow rates to help select the optimum tubing size.
Figure 6-2
Figure 6-2. Pressure Drop and Travel Time for 0.125" (3.2 mm) ID Tubing
Figure 6-5
100
200
300
400
500
600
700
800
900
1000
0 2 4 6 8 101214161820
Tube Length (m)
Pressure (mB)
8 slpm 10 slpm 13 slpm 17 slpm 22 slpm
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
02468101214161820
Tube Length (m)
Time (s)
8 slpm 10 slpm 13 slpm 17 slpm 22 slpm
100
200
300
400
500
600
700
800
900
1000
0 102030405060
Tube Length (m)
Pressure (mB)
10 slpm 13 slpm 17 slpm 22 slpm 28 slpm
0
0.5
1
1.5
2
2.5
3
3.5
0 102030405060
Tube Length (m)
Time (s)
10 slpm 13 slpm 17 slpm 22 slpm 28 slpm
Figure 6-3. Pressure Drop and Travel Time for 0.170" (4.3 mm) ID Tubing
100
200
300
400
500
600
700
800
900
1000
0 20 40 60 80 100 120 140 160
Tube Length (m)
Pressure (mB)
13 slpm 17 slpm 22 slpm 28 slpm 35 slpm
0
2
4
6
8
10
12
0 20 40 60 80 100 120 140 160
Tube Length (m)
Time (s)
13 slpm 17 slpm 22 slpm 28 slpm 35 slpm
Figure 6-4. Pressure Drop and Travel Time for 0.250" (6.4 mm) ID Tubing
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