Chemical dosimeter with constant flow air sampling pump - has integrator and amplifier controlling variable drive pump connected to air filter

摘要

The chemical dosimeter is for individual use and collects on a filter particles or vapours present in an air stream which is being pumped through the dosimeter at a constant rate. A variable drive pump is connected to the filter and is driven by an electric motor and controlled by a feed back circuit of an integrator and an amplifier to maintain a constant flow of air through the dosimeter. The integrator receives a signal from a pressure switch that detects changes in the flow of the air stream through the dosimeter by a change in a pressure drop of the air which is being pumped through an orifice. The dosimeter is worn by an individual and at the termination of a period of time, such as a work day, the filter is removed and the collected contents are analysed by conventional techniques such as gas chromatography to determine a level of exposure of the individual using the dosimeter.