Abstract: An improved personal sampling pump design makes use of non-circular diaphragms within the pump assembly to provide a compact, space saving design. Both upstream and downstream dampers are employed to reduce pulsation in the airflow. Flow control is achieved by monitoring the back pressure created by a flow restriction or adjustable valve located at the sampler's outlet. The created pressure is monitored by a pressure sensor and is directly related to inlet flow rate. The use of an adjustable restriction on the outlet provides increased dynamic range of the flow measurement system without excessive loading to the pump.

Abstract: In a personal air sampling system, flow control is achieved by monitoring the back pressure created by a local flow restriction (eg. an adjustable valve) located at the sampler's outlet. The pressure drop across the restriction is monitored by a pressure sensor and is directly related to inlet flow rate. The use of an adjustable restriction on the outlet provides increased dynamic range of the flow measurement system without excessive loading to the pump. A signal conditioning circuit takes the signal from the pressure sensor and feeds it to an analogue to digital converter which in turn feeds it to a microprocessor. The microprocessor controls the pump drive circuitry such that a constant inlet flow rate is maintained. The user can select the desired operating flow rate to an accuracy such that an additional external flow measuring device is not required. A pump of the system makes use of non-circular diaphragms within the pump assembly to provide a compact, space saving design.