The present invention is concerned with a controlled sampler device which draws a gas through a contaminant collection device. The controlled sampler comprises an inlet to the sampler; a pump adapted to draw a gas through the inlet; a reference element that provides a reference signal; a feedback element with an output; a differential pressure transducer to compare the reference signal with the feedback signal to provide an error signal that is linearly related to selected and measured values; an integrator with an input connected to the output of the differential pressure transducer and to a summer; and means between the differential pressure transducer and the summer to provide a signal to the summer which is proportional to the error signal, which is passed to a driver which regulates the speed of an electric motor to change the flow rate to reduce the error signal to a null.
A fluid flow control system maintains a constant, controllable, low flow rate through an orifice; intermittently operates a pump at an efficient, relatively high flow rate; and moderates flow between the pump and the orifice. The system is energy efficient and accurate.
A device for measuring and automatically controlling the volumetric rate of air through an air handling system used in connection with clean rooms. A desired volumetric air rate is maintained by measuring air pressure differentials between different locations in the system. The volumetric air rate is adjusted by using a variable frequency drive to adjust the speed of the fan in response to a measured pressure differential.
A sampling system for capturing samples of trace elements in ambient air comprises a multi-port valve coupled to a plurality of sorbent tubes. Each tube is connected to the multi-port valve by means of pairs of the valve ports. The multi-port valve is constructed and operated in a predetermined sequence to create a flow path through the multi-port valve. The flow path directs an air sample to only one connected sorbent tube at a given time and for a given time interval.
Portable air sampling apparatus and methods are provided for passively and/or intermittently sampling air in the breathing zone of a person over extended periods of time. The presence of airborne contaminants can be monitored, as well. Air sampling system performance can be continuously measured and recorded within a data logger. In addition, physical activity levels of a person wearing a portable air sampling system can be continuously monitored and recorded within the data logger. An input device communicates with the data logger and allows a user to store information about his or her personal activities in the data logger. A receiver in communication with the data logger can receive data from remotely located communications devices, such as a Global Positioning System (GPS) signals. A transmitter in communication with the data logger can transmit data from the data logger to remotely located communications devices.
An air or gas sampling device utilizes a small tube calibrated under isothermal conditions. The relationship of pressure at the input end of the tube to flow is plotted and stored in a microprocessor for comparison with pressure monitored during sample pumping. Pulsations in flow caused by the air or gas pump can be neutralized by a damper comprising a small chamber having a diaphragm for one wall.
