Hach-Lange BUHLER 1027 2000 - Manual (Page 19)

Operation
Page 19 Manual Bühler 2000
Flow-proportional sampling system
The characteristic features of the flow-proportional sampling are:
• fixed
sampling interval (e. g. every 10 min) with
• variable sample volume (related to the mA-signal (flow))
At the variable dosing system, the sample volume is automatically changed according to the analogue
flow signal.
Example:
- the selected range is 4 to 20 mA (option 0 – 20 mA)
- the maximum sample volume at 20 mA is fixed to 200 ml.
That means at an analogue signal of e.g. 10 mA, a 100 ml sample would
be extracted. Thus the sample extraction is always proportional to the flow.
This sampling mode supplies very good, representative results as even if flow is very low (e.g.
discharges at night) a sample extraction is still carried out in fixed time intervals.
For comparison a short description of the flow-dependent sampling mode:
The characteristic features of the flow-dependent sample extraction are:
• variable sampling interval (according to the mA-signal (flow)) with
• fixed
sample volume (e.g. 100 ml)
In the flow-dependent sampling mode, a sample is e.g. always extracted after 10 m³, that means the
signal of the flow meter is totalized.
In case of very low flow quantities (e.g. discharges at night) it is possible that e.g. 2-3 hours pass until
the set 10 m³ are reached again and a sample is extracted.
Remark:
That means if there is an accident (e.g. discharge of chemicals) during this period, there
will be no sample. However, a sample would have been very important for an analysis and
the taking of countermeasures.
Flow-proportional sampling system - structure
Structure:
1. Electrodes 2
2. Measuring tube
3. Electrodes 1
4. Connection for aeration
5. Dosingvessel
6. Pinsch Valve
7. Cleaning cap of gas drap
8. Inlet connection