Feedback flow control sampler

Figure 4 shows a simple version of a feedback flow control sampler system. An orifice and pressure switch are used to monitor air flow. 

Figure 4. Feedback flow control sampler system...

The following data illustrates the performance of feedback flow control samplers under test conditions which represent field conditions. Figure 11 shows the flow rate stability versus time for a sampler operated on its battery. The flow control system maintained a constant flow rate even though the battery was discharging(3). 

A simple positive-displacement sampler system is shown in Figure 3. The basic system contains a battery and motor connected to a positive-displacement pump mechanism and provides an efficient means for moving air through the sampler. In order to provide feedback flow control the system must be expanded to include the means to monitor air flow through the pump to compensate for flow variations. 

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