Gas detecting apparatus with means to record detection signals in superposition for improved signal-to-noise ratios

Claim 2

Apparatus in accordance with claim 2, wherein said output circuit includes an impedance across which a potential is developed in accordance with said signals.

Claim 3

Apparatus in accordance with claim 3, said sensing means further comprising an amplifier connected to said impedance for amplifying the voltage developed across said impedance.

Claim 4

Apparatus in accordance with claim 4, said discriminating means comprising a continuous loop magnetic tape recorder having means for recording the output of said amplifier on said continuous loop repetitively such that signals representing ions of the same mass are recorded in coincidence so as to reinforce one another.

Claim 5

Apparatus in accordance with claim 5, wherein said ion-producing means has means synchronized with the operation of said recorder for rendering the ion-producing means operative periodically.

Claim 6

Apparatus for detecting a substance in a gaseous sample, which comprises an envelope, a pair of principal electrodes spaced apart in said envelope, means for introducing a gaseous sample into said envelope, means including an ionizer associated with one of said principal electrodes for producing reactant ions which react with molecules of said substance to produce product ions, means for applying a drift field between said electrodes to cause said ions to drift toward the other of said electrodes, an output circuit connected to said other electrode, shielding means disposed between said electrodes adjacent to said other electrode for shielding said other electrode and said output circuit from ion displacement currents in said envelope but for permitting substantially all of said ions to pass through said shielding means to said other electrode, the length of the mean free path of said ions in said envelope being very much smaller than the dimensions of said envelope, said output circuit including means for sensing the presence of ions passed between said shielding means and said other electrode and for generating electrical signals in response thereto, and means for discriminating between ions of different mass represented by said electrical signals, said apparatus including means for providing the ions at said shielding means in timed cycles, said discriminating means including means for producing indications dependent upon the timing of said electrical signals with respect to the beginning of the corresponding cycle.

Claim 7

Apparatus for detecting a substance in a gaseous sample, which comprises an envelope, a pair of principle electrodes spaced apart in said envelope, means for introducing a gaseous sample into said envelope, ionizing means associated with one of said electrodes for producing ions from said sample, an output circuit connected to the other of saId electrodes, means for applying a drift field between said electrodes to cause said ions to drift toward said other electrode, said output circuit including means for sensing the presence of ions and for generating electrical signals in response thereto, and a continuous-loop-medium recorder having means for recording on said medium a signal derived from said output circuit repetitively in superposition such that signals representing ions of the same mass are recorded in coincidence so as to reinforce one another.

Claim 8

Apparatus in accordance with claim 8, wherein said medium is a magnetic tape.

Claim 9

Apparatus in accordance with claim 8, wherein said ionizing means has means for rendering it operative periodically in synchronism with the operation of said recorder.

Claim 10

Apparatus for detecting a substance in a gaseous sample, which comprises an envelope, a pair of principle electrodes spaced apart in said envelope, means for introducing a gaseous sample into said envelope, means for applying a drift field between said electrodes, cyclically operable ionizing means associated with one of said electrodes for producing reactant ions which react with molecules of said substance to produce product ions, an output circuit connected to the other of said electrodes, ion gate means disposed between said electrodes adjacent to said other electrode, means for operating said ionizing means cyclically, and means for opening said ion gate means at a predetermined time after said ionizing means has operated and for closing said ion gate means when said ionizing means is operated again, the length of the mean free path of said ions in said envelope being very much smaller than the dimensions of said envelope, said output circuit including means for sensing the presence of ions and for generating electrical signals in response thereto.

Claim 11

Apparatus in accordance with claim 11, wherein said means for opening and closing said gate means comprises a square wave generator, and wherein said means for operating said ionizing means comprises means synchronized with said square wave generator.

Claim 12

Apparatus in accordance with claim 11, said output circuit comprising an electrometer amplifier and signal indicating means connected to said electrometer amplifier.

Claim 13

Apparatus in accordance with claim 11, wherein said means for opening and closing said gate means includes means for varying the time at which said gate means is opened relative to the preceding operation of said ionizing means.

Claim 14

Apparatus in accordance with claim 14, further comprising means for comparing the signals produced in said output circuit when said gate means is opened at different times and for producing a difference signal.