ADDING RELATIVE HUMIDITY TO TRACE CONCENTRATION GAS STANDARDS IN A PERMEATION SYSTEM

摘要

Gas sensor sensitivity levels have increased in equipment where atmospheric conditions, such asrnrelative humidity, directly affect test results. Calibrating for changes in relative humidity in tracernlevel gas concentrations has generated the need for effectively adding relative humidity to thernoutput gas of a permeation system. There are several techniques available for adding knownrnlevels of humidity to pure gas streams, but those techniques do not directly apply to therndynamics of a permeation system.rnSpecific factors have to be considered for controlling broad ranges of relative humidity inrnvarying dilution gas streams without compromising the concentration of other analytes in thernoutput of the permeation system. Relative humidity can be added to the calibration gas streamrnwithout affecting the final concentration requirement by incorporating a module that utilizes arnsplit-flow technique with variable pressure control and variable flow control. This module canrnbe used in different permeation system scenarios or bypassed when a dry calibration gas isrnneeded.