Hach SIGMA 900 - Manual (Page 30)

Page 30
Flow Proportional Operation 8544operations.fm
Section 4
Use the following examples to help you determine the value that you need to
enter when programming for sampling based on counts.
Example 1
You want to collect 24 samples over a 24-hour period on a 4–20 mA flow
proportional basis.
Average Flow Rate = 3.5 mgd (average flow rate over the 24-hour period)
Maximum Flow Rate = 10 mgd
a = 1440 minutes
1. Calculate Q.
2. Calculate t.
3. Multiply Q x t.
Therefore, the value entered for INTV = _ _ _ _ CNTS is 21.
Example 2
You want to collect 48 samples over a 24-hour period on a 4–20 mA flow
proportional basis.
Average Flow Rate = 1.75 mgd (average flow rate over the 24-hour period)
Maximum Flow Rate = 3 mgd
a = 1440 minutes
1. Calculate Q.
2. Calculate t.
3. Multiply Q x t.
Therefore, the value entered for INTV = _ _ _ _ CNTS is 18.
Example 3
You want to collect 96 samples over a 24-hour period on a 4–20 mA flow
proportional basis.
Average Flow Rate = 0.52 mgd (average flow rate over the 24-hour period)
Maximum Flow Rate = 2 mgd
a = 1440 minutes
1. Calculate Q.
Q
Average Flow Rate
Maximum Flow Rate
------------------------------------------------------
3.5 mgd
10 mgd
--------------------- 0.35 mgd = = =
t
a
n
---
1440 min
24 samples
------------------------------ 60 min/sample = = =
0.35 mgd 60 min/sample
×
21 =
Q
Average Flow Rate
Maximum Flow Rate
------------------------------------------------------
1.75 mgd
3 mgd
------------------------- 0.583 mgd = = =
t
a
n
---
1440 min
48 samples
------------------------------ 30 min/sample = = =
0.583 mgd 30 min/sample
×
17.5 =
Q
Average Flow Rate
Maximum Flow Rate
------------------------------------------------------
0.52 mgd
2.0 mgd
------------------------- 0.26 mgd = = =