Assembly and method of obtaining a controlled gas mixture
AssigneeTylan Corporation
InventorDan B. LeMay
Life of this patent
Estimating the term…
Abstract
Apparatus and method for obtaining a controlled gas mixture of predetermined proportionality using a temperature dependent permeation tube or like source for the addition of a small amount of a constituent gas in a higher flow rate carrier gas. A thermistor having a negative coefficient of resistance is associated with the permeation source and electrically connected to a flow controller for the carrier gas to automatically regulate the flow rate of the carrier gas in accordance with temperature variation of the permeation source.
Claims8
Apparatus for obtaining a controlled mixture of a first gas and a carrier gas, comprising:
- a mass flow controller for delivering carrier gas at a controlled rate of flow;
- a source of said first gas which emits said gas at a mass flow rate which is a repeatable function of the ambient temperature of said source;
- means for adding said first gas into carrier gas delivered by said mass flow controller for dilution in predetermined proportionality with said carrier gas;
- and
- means for automatically changing the flow rate of said mass flow controller in accordance with variations in said ambient temperature of said source to compensate for temperature-dependent changes in the emission rate therefrom whereby to substantially maintain their proportionality.
Apparatus for obtaining a controlled mixture of first gas and carrier gas, comprising:
- a mass flow controller for delivering carrier gas at a controlled rate of flow proportionally responsive to a voltage applied thereacross;
- a permeation source containing said first gas for emitting said first gas at a mass flow rate which is a repeatable function of the ambient temperature of said source and which is lower than said controlled rate, into carrier gas delivered by said mass flow controller for dilution in a predetermined proportionality with said carrier gas, said permeation source having a significant positive temperature coefficient of emission;
- and
- an electrical circuit including, as components thereof, a source of said voltage for said mass flow controller, a thermistor, closely and physically associated with said permation source, having a negative temperature coefficient of resistance, and a voltage-dividing means for adjusting the temperature coefficient resistance of said circuit for substantially maintaining said proportionality.
Dependencies are inferred from the claim text.