A gas and vapor generation system with programmed automatic cyclic output

This paper describes a gas and vapor generation system that can be programmed to produce contaminant concentrations that are variable with time and that are repeatable. The system utilizes an electromechanical programmer designed to vary a potentiometer in accordance with variations in a program curve manually etched in the surface of a special program card. The output of this programmer is interfaced with a linear mass flow controller which will control either the contaminant stream or the dilution air stream to achieve the desired range of contaminant concentrations. The results of some experiments with carbon monoxide and toluene show repeatability of one to three percent for periodically repeated cycles, and demonstrate the flexibility of the system.