| 摘要 |
<p>An Improved Pump Unit For Sampling Air An improved pump unit for sampling air that operates at a constant air flow rate in the range of 5-5000 cc/min, having a filter for removing particles or vapors from the air stream, an air accumulator, a variable drive pump optionally with a bypass, an electric motor for driving the pump, an optional air reservoir, an orifice which creates a pressure drop in the air stream, an optional bypass for the orifice and a pressure switch connected in parallel to the orifice which monitors a change in the air pressure drop; the improvement in the pump is the use of a digital circuit electrically connected to the pressure switch and a closed loop control means electrically connected to the digital circuit and motor; a digital signal determines the open or closed position of the switch and the control means and allows current to flow or not flow to the motor driving the air pump to provide a constant flow of air through the unit: the pump unit is worn by a worker or is placed in a work area and at the termination of a period of time, such as a work day. the filter is removed and the contents collected are analyzed by conventional techniques such as gas chromatography to determine a level of exposure of the individual or the level of exposure of people working in that area.</p> |
