Hach Polymetron 9611sc Installation Manual page 10

Keep the sample lines as short as possible to prevent the accumulation of bottom sediment. The
sediment can absorb some of the analyte from the sample and cause low readings. The sediment
can later release the analyte and cause high readings. This exchange with the sediment also causes
a delayed response when the analyte concentration in the sample increases or decreases.
Figure 6 Sampling methods
1 Air
Set the bypass flow rate
Do not loosen the screw by more than 4 turns for the multi-stream.
The bypass flow can be adjusted when the analyzer is in shutdown mode. Adjust the flow rate of the
sample bypass line with the flow valve as shown in
on page 20 for the sample flow rate range. Use an external meter to measure the flow rate of the
sample bypass line. Increase the flow rate of the sample bypass line when the process stream is far
from the analyzer for a faster response to changes in the process stream.
Figure 7 Bypass flow rate adjustment - one stream
10 English
2 Sample flow
N O T I C E
Figure 7 or Figure 8. Refer to Specifications