EP0119772A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Improvements in or relating to determining the presence of a contaminant in a gaseous carrier
Assignee: UK Secretary of State for Social Services
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Filing: 1984-02-27
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Granted: —
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Expires: 2004-02-27
Abstract
Abstract The invention is directed more especially to the monitoring of any fine particulate content of medical gases, eg those distributed through pipe lines. Fine dust particles, in a fairly well defined size range, are harmful if inhaled, especially by a sick person. To avoid the hazard, gas supplies, eg of oxygen, must be monitored for such dust. The invention provides that a stream of gas deposits any particles carried by it on a first crystal oscillator (12) the frequency of which is thereby varied. Frequency change is measured by beating the frequency of said crystal with that of a second similar crystal (14) not exposed to the gas stream. Cleaning of the first crystal (12) after each test is avoided by a preliminary comparison (48 - 50) of the frequency of the first crystal (12) with a predetermined value, to show whether the crystal frequency has departed from the linear portion of its mass/ frequency characteristic. Provided the first crystal (12) continues to operate in said linear portion, repeated tests may be carried out without need for cleaning.
Inventors
- 👤 John Kevin Thornley
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-29 20:44
CPC Classifications
G; G01; G01N; G01N29/00; G01N29/02; G01N29/036; G01N2291/00; G01N2291/02; G01N2291/025; G01N2291/0256
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
166 words
A method of detecting the presence of a contaminant in a gaseous carrier characterised in that, it includes the steps of allowing oscillations from a first crystal oscillator (12) to produce a beat frequency with oscillations from a second crystal oscillator (14) exposed to substantially the same environmental conditions affecting its stability as said first crystal, except that said second crystal oscillator (14) is not exposed to contaminant; comparing a first value proportional to said beat frequency with a first predetermined value to determine whether the first crystal oscillator (12) is initially operating within the linear portion of its mass/frequency characteristic; feeding carrier gas to said crystals so that any contaminant in said gas can act upon said first crystal oscillator (12) to change the effective mass thereof; and comparing a second value proportional to the beat frequency between said oscillators (12, 14) with a second predetermined value to indicate any change in mass of said first crystal oscillator (12) due to action thereon of contaminant.
Claim 2
Independent Claim
166 words
A method of detecting the presence of a contaminant in a gaseous carrier characterised in that, it includes the steps of allowing oscillations from a first crystal oscillator (12) to produce a beat frequency with oscillations from a second crystal oscillator (14) exposed to substantially the same environmental conditions affecting its stability as said first crystal, except that said second crystal oscillator (14) is not exposed to contaminant; comparing a first value proportional to said beat frequency with a first predetermined value to determine whether the first crystal oscillator (12) is initially operating within the linear portion of its mass/frequency characteristic; feeding carrier gas to said crystals so that any contaminant in said gas can act upon said first crystal oscillator (12) to change the effective mass thereof; and comparing a second value proportional to the beat frequency between said oscillators (12, 14) with a second predetermined value to indicate any change in mass of said first crystal oscillator (12) due to action thereon of contaminant.
Claim 3
Dependent Claim
196 words
Apparatus for detecting the presence of a contaminant in a gaseous carrier characterised by a first piezo electric crystal oscillator (12); carrier gas feed measn (10) enabling contaminant in said gas to act upon said first crystal (12) to change the effective mass thereof; a second piezo electric oscillator (14) arranged so that the second crystal (14) is exposed to substantially the same environmental conditions affecting its stability as said first crystal (12), except that shielding means (22) are provided so that the second crystal (14) is not exposed to contaminant; beat detecting means (30) to detect a beat frequency between the first frequency of the first oscillator (12) and the second frequency of the second oscillator (14); timing and switching means (40) arranged to transmit first and second values proportional to the beat frequency to comparator means (48) to compare said values respectively with first and second predetermined values, whereby comparison between said first values indicates whether the said first crystal (12) is initally operating within the linear portion of its mass/frequency characteristic, and comparison between said second values indicates any change in mass of said first crystal (12) due to action thereon of contaminant.
Claim 4
Dependent Claim
196 words
Apparatus for detecting the presence of a contaminant in a gaseous carrier characterised by a first piezo electric crystal oscillator (12); carrier gas feed measn (10) enabling contaminant in said gas to act upon said first crystal (12) to change the effective mass thereof; a second piezo electric oscillator (14) arranged so that the second crystal (14) is exposed to substantially the same environmental conditions affecting its stability as said first crystal (12), except that shielding means (22) are provided so that the second crystal (14) is not exposed to contaminant; beat detecting means (30) to detect a beat frequency between the first frequency of the first oscillator (12) and the second frequency of the second oscillator (14); timing and switching means (40) arranged to transmit first and second values proportional to the beat frequency to comparator means (48) to compare said values respectively with first and second predetermined values, whereby comparison between said first values indicates whether the said first crystal (12) is initally operating within the linear portion of its mass/frequency characteristic, and comparison between said second values indicates any change in mass of said first crystal (12) due to action thereon of contaminant.
Claim 5
Dependent Claim
67 words
Apparatus according to claim 2 characterised in that the timing and switching means (40) is arranged to give a signal, after transmission of said first value, to commence feed of carrier gas through said carrier gas feed means (10), and after a predetermined time interval, and before transmission of said second value, a signal to stop feed of carrier gas through said carrier gas feed means (10)..
Claim 6
Dependent Claim
24 words
Apparatus according to claim 3 characterised in that said signals to commence and to stop feed of carrier gas are audible and/or visible signals.
Claim 7
Dependent Claim
29 words
Apparatus according to claim 3 characterised in that said signals to commence and to stop feed of carrier gas are arranged to operate a carrier gas feed valve automatically.
Claim 8
Dependent Claim
30 words
Apparatus according to any one of claims 3, 4 and 5 characterised in that the predetermined time interval is arranged to be dependent on the pressure of the carrier gas.
Claim 9
Dependent Claim
19 words
Apparatus according to claim 6 characterised in that the time interval is selectable manually in relation to said pressure.
Claim 10
Dependent Claim
39 words
Apparatus according to any one of the preceding claims characterised in that it includes a frequency to voltage converting means (32) to produce an output voltage value proportional to the beat frequency output of said beat detecting means (30).
References Cited (Backward Citations)
No citation records indexed.
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