Patent US3665441A successfully refreshed from Google Patents.
US3665441A
Expired / Lapsed
US
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Method and apparatus for detecting aerosols
Assignee: Edwards Co Inc
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Filing: 1970-09-14
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Granted: 1972-05-23
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Expires: 1990-09-14
Abstract
Abstract Apparatus whereby the presence of aerosols in an atmosphere is detected by measuring the level of the ion current through a chamber open to the atmosphere, wherein an electric field impressed across the electrodes of the chamber is selected within a range of values maximizing the effect of aerosols on the level of the current through the chamber and the signal developed relative to the chamber current is detected by circuitry including a metal oxide silicon field effect transistor.
Inventors
- 👤 Michael Suchomel
- 👤 William Tipton
- 👤 James H Burnett
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 08:00
CPC Classifications
G; G08; G08B; G08B17/00; G08B17/10; G08B17/11
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
243 words
Apparatus for detecting the presence of aerosols in the atmosphere having reference and measuring ionization chambers connected in series for sensing the presence of aerosols and a detector connected to a midpoint between the chambers for indicating an abnormal condition of the chambers wherein the improvement comprises: a low voltage regulated power supply for energizing both the chambers and the detector and wherein the detector comprises: a field effect transistor having one of its gates connected to the midpoint for delivering an abnormal output in response to presence of aerosols in the measuring chamber; a unijunction transistor having its gate electrode connected to the output of the field effect transistor for delivering an output in response to output above a normal level of the field effect transistor; an integrating circuit connected to the gate of the unijunction transistor for rendering the unijunction transistor operable to deliver an output only after an abnormal output of the field effect transistor has persisted for a selected time interval; a feedback circuit connected from the unijunction transistor to the field effect transistor for increasing the sensitivity of the detecting apparatus in response to the unijunction transistor being turned on; silicon controlled rectifier means having its gate circuit governed by an output of the unijunction transistor for turning on an indicator; and a rate of rise filter for permitting actuation of the indicator only if output of the silicon controlled rectifier has persisted for a selected time interval.
Claim 2
Dependent Claim
243 words
Apparatus for detecting the presence of aerosols in the atmosphere having reference and measuring ionization chambers connected in series for sensing the presence of aerosols and a detector connected to a midpoint between the chambers for indicating an abnormal condition of the chambers wherein the improvement comprises: a low voltage regulated power supply for energizing both the chambers and the detector and wherein the detector comprises: a field effect transistor having one of its gates connected to the midpoint for delivering an abnormal output in response to presence of aerosols in the measuring chamber; a unijunction transistor having its gate electrode connected to the output of the field effect transistor for delivering an output in response to output above a normal level of the field effect transistor; an integrating circuit connected to the gate of the unijunction transistor for rendering the unijunction transistor operable to deliver an output only after an abnormal output of the field effect transistor has persisted for a selected time interval; a feedback circuit connected from the unijunction transistor to the field effect transistor for increasing the sensitivity of the detecting apparatus in response to the unijunction transistor being turned on; silicon controlled rectifier means having its gate circuit governed by an output of the unijunction transistor for turning on an indicator; and a rate of rise filter for permitting actuation of the indicator only if output of the silicon controlled rectifier has persisted for a selected time interval.
Claim 3
Dependent Claim
82 words
The apparatus of claim 1 wherein said integrating circuit comprises: a resistor and capacitor serially coupled across the power supply, and a discharge circuit for said capacitor including: an output resistor coupled to the drain of said FET and a diode connected normally to discharge said capacitor through said output resistor, the diode becoming biased to be non-conductive upon the occurrence of an abnormal output of said FET thereby permitting the capacitor to charge to a level sufficient to activate said unijunction.
Claim 4
Dependent Claim
37 words
The apparatus of claim 1 wherein said rate of rise filter comprises a resistor and capacitor serially coupled with said indicator for permitting actuation of said indicator in accordance with the time constant of said resistor-capacitor combination.
Claim 5
Dependent Claim
37 words
The apparatus of claim 1 further including: a zener diode means coupled across the chamber for regulating the potential across the chambers to a predetermined value regardless of loading of the power supply by the detection circuit.
Claim 6
Dependent Claim
45 words
The apparatus of claim 1 wherein said feedback loop comprises: a potentiometer coupled between the power supply and the unijunction transistor and having is slider terminal coupled to the source electrode of said field effect transistor whereby the sensitivity of said FET may be adjusted.
Claim 7
Dependent Claim
83 words
The apparatus of claim 5 including an output circuit for said Unijunction transistor comprising: a capacitor coupled to the junction of the potentiometer and the unijunction transistor, said capacitor charged in accordance with the impedance of said potentiometer and capacitor combination when said unijunction is in a non-conductance state and discharged through said unijunction for delivering the output when said unijunction is in a conductance state; and a zener diode coupled across said unijunction and capacitor for regulating the bias on said unijunction.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-05-23 | 1975-11-22 | 1976-05-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-05-23 | 1979-11-22 | 1980-05-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-05-23 | 1983-11-22 | 1984-05-23 | $7700.00 | Window Closed / Lapsed |