High impedance gaseous ion sensing and detection system

Claim 2

An environmental ion sensing apparatus for detecting a change in the charge in environmental borne elements, comprising an amplifying circuitry including an input means having a high input impedance, a capacitance sensing means including a pair of spaced capacitance electrode means one of which is connected to a reference potential to define a reference electrode and the other of which is directly subjected to the surrounding environment to define a sensing electrode with the charge gradient of the sensing electrode directly related to the environmental charge concentration, means connecting said sensing electrode to the high impedance input means of the amplifying means, and a low leakage semiconductor diode means connected in parallel with said sensing means, said diode means being connected to maintain a high impedance of low noise characteristic across the sensing means and thereby prevent accumulation of charge on the sensing means.

Claim 3

The apparatus of claim 1 wherein diode means is a Zener diode.

Claim 4

The apparatus of claim 1 wherein the charge sensitive capacitance means includes a reference electrode in the form of an enclosure surrounding the sensing electrode, a large resistance connecting said sensing electrode to the reference electrode to prevent charge accumulation, and a high surface and bulk resistivity insulator mounting said sensing electrode to prevent by-passing of said diode means.

Claim 5

The apparatus of claim 1 wherein said reference electrode includes a central opening, said sensing electrode having a mounting opening coaxially aligned with said central opening, a sensing probe secured within said mounting opening and extending outwardly through said central opening to subject the sensing probe to the movement of intruding static charged bodies into the area to provide an intrusion detection response.

Claim 6

The apparatus of claim 4 and having a high bulk and surface resistivity insulator between said central opening and said probe.

Claim 7

The apparatus of claim 1 wherein the amplifying circuitry includes a field effect transistor having the gate connected to the sensing electrode to define the high input impedance, an operational amplifier having an input connected to the output of the field effect transistor to provide an amplified signal corresponding to the charge gradient on said sensing electrode, a level detection and alarm circuit connected to the output of the operational amplifier and responsive to selected changes of negative and positive voltages from a quiescent operating voltage to indicate the corresponding selected chang in the capacitance circuit gradient.

Claim 8

The apparatus of claim 6 wherein the level detection and alarm circuit includes a pair of transistors having their inputs connected in common to the output of the operational amplifier and oppositely responding to the changes of negative and positive potential voltages from the quiescent operating voltage and output means connected to both of said transistors and responsive to a selected corresponding change in the conductivity of either one of said pair of transistors.

Claim 9

The apparatus of claim 1 wherein the reference electrode is a semispherical dish-shaped aperture plate having a plurality of apertures, a support connected to said plate, said sensing electrode being a solid semispherical dished plate having a coaxially mounted terminal connected to said sensing electrode and extending rearwardly through said support, and coupled to the terminal insulator to mount the sensing electrode in equicircumferential spaced and insulated relationship to the inner surface of said reference electrode.

Claim 10

The apparatus of claim 1 wherein said reference electrode is removably mounted with respect to said sensing electrode whereby said sensing electrode can be removed to directly expose said sensing electrode to the surrounding atmosphere to subject the sensing electrode to the movement of intruding static charged bodies into the area to provide an intrusion detection response.

Claim 11

An environmental ion sensing apparatus for detecting a change in the charge in environmental borne elements, comprising an amplifying circuitry including an input means having a high input impedance, a capacitance sensing means including a pair of spaced capacitance electrode means one of which is connected to a reference potential to define a reference electrode and the other of which is directly subjected to the surrounding environment to define a sensing electrode with the charge gradient of the sensing electrode directly related to the environmental charge concentration, means connecting said sensing electrode to the high impedance input means of the amplifying means, a dual field effect transistor connected as a differential amplifier with a first gate connected to the sensing electrode to define a high input impedance and having a second gate, a complementary pair of transistors having an input connected to the output of the dual field effect transistor and an output means connected in said second gate, and operational amplifier means having an input connected to the output means of the pair of transistors to provide an amplified signal corresponding to the charge gradient on said sensing electrode, and a detection circuit connected to the output of the operational amplifier and responsive to selected changes of both a negative voltage and a positive voltage from a quiescent operating voltage to indicate the corresponding selected change in the capacitance charge gradient.

Claim 12

An environmental ion sensing apparatus for detecting a change in the charge in environmental borne elements, comprising an amplifying circuitry including an input means having a high input impedance, a capacitance sensing means including a pair of spaced capacitance electrode means one of which is connected to a reference potential to define a reference electrode and the other of which is directly subjected to the surrounding environment to define a sensing electrode with the charge gradient of the sensing electrode directly related to the environmental charge concentration, means connecting said sensing electrode to the high impedance input means of the amplifying means, a dual field effect transistor connected as a differential amplifier with a first gate connected to the sensing electrode to define a high input impedance and having a second gate, a complementary pair of transistors having an input connected to the output of the dual field effect transistor and an output means connected in said second gate, and operational amplifier means having an input connected to the output means of the pair of transistors to provide an amplified signal corresponding to the charge gradient on said sensing electrode, and a detection circuit connected to the output of the operational amplifier and responsive to selected changes of both a negative voltage and a positive voltage from a quiescent operating voltage to indicate the corresponding selected change in the capacitance charge gradient.

Claim 13

The apparatus of claim 10 wherein operational amplifier means includes a pair of cascaded operational amplifiers including a first operational amplifier having one input connected to the output of the pair of transistors, and having a second input, a feedback network including a voltage dividing bias supply connected to said second input and having a high impedance transistor controlling the signal to said second input, said feedback network including a resistive-capacitive branch conNecting the output of the second operational amplifier to said high impedance transistor.

Claim 14

The apparatus of claim 11 wherein the high impedance transistor is a field effect transistor connected in series with a resistor to a circuit common potential supply and having a gate, said resistive-capacitive branch includes a timing resistor in series with the gate and the output means of the second operational amplifier and a capacitor connecting the gate to said common potential supply.

Claim 15

The apparatus of claim 12 having a diode means connected across said timing resistor.

Claim 16

The apparatus of claim 11 wherein each of said operational amplifiers includes a capacitive feedback means to suppress high frequency above a selected level.