Electricity: measuring and testing – Using ionization effects – For analysis of gas – vapor – or particles of matter
Reexamination Certificate
2001-07-24
2004-08-24
Le, N. (Department: 2858)
Electricity: measuring and testing
Using ionization effects
For analysis of gas, vapor, or particles of matter
C073S023220, C073S035080
Reexamination Certificate
active
06781384
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to devices that may be used to generate and control electrical discharges in ionization sources of analytical devices.
2. Description of the Related Art
Gas chromatography devices can separate a gas mixture into the mixture's component gases and, after the separation, can quantify each component gas. A detector
10
used for analyzing a component gas is illustrated in FIG.
1
A. The type of detector
10
illustrated in
FIG. 1A
is a discharge ionization detector that has previously been disclosed in U.S. Pat. No. 4,975,648 to Lawson et. al., the contents of which are incorporated herein by reference.
The detector
10
illustrated in
FIG. 1A
includes a housing
20
that has, formed within it, a discharge chamber
30
, and ionization chamber
40
, and an aperture
50
that connects the discharge chamber
30
and the ionization chamber
40
. Also formed within the housing
20
are a surrounding gas inlet
60
that leads to the discharge chamber
30
, a sample inlet
70
that leads to the ionization chamber
40
and a sample outlet
80
that also leads to the ionization chamber
40
.
Within the discharge chamber
30
are a pair of spark-generating electrodes
90
. One of the spark electrodes
90
has a small ball at the end thereof, while the other spark electrode
90
has a sharpened tip. Each of the spark electrodes
90
is connected to a separate pin
100
that supports the electrode
90
attached to it at a spatial location within the discharge chamber
30
.
Each of the pins
100
is contained within a separate sheath
110
that protrudes from both sides of a sealing flange
120
. The sealing flange
120
can be screwed into or otherwise fixed to one end of the housing
20
.
Outside of the housing
20
and wrapped around each sheath
110
is a separate insulating plug
130
. Each plug
130
leads to a separate wire
140
and each of the wires
140
is electrically connected to the same electronic circuit
150
.
The electronic circuit
150
provides electrical current to each of the spark electrodes
90
during operation of the detector
10
. The timing, duration and intensity of the sparks created between the electrodes
90
is controlled by the electronic circuit
150
.
A collector electrode
160
and an emitter electrode
170
are position within the ionization chamber
40
of the detector
10
and are held in place via a bottom flange
180
that is fitted into the housing
20
. A pair of wires
190
connect to the collector electrode
160
and the emitter electrode
170
, respectively, and lead to a pair of electrical couplings
200
. The wires
190
provide current to the collector electrode
160
and emitter electrode
170
when the detector
10
is in operation.
During operation, a surrounding or carrier gas, such as helium, is allowed to flow into the discharge chamber
30
through the surrounding gas inlet
60
. The spark electrodes
90
are then provided with current from the electronic circuit
150
and are placed in close enough proximity to generate an electrical arc or spark across the electrodes
90
. The electrical spark causes the surrounding gas to discharge photons and metastables at a characteristic energy level.
The photons and metastables then travel through the aperture
50
of the housing
20
and into the ionization chamber
40
that is filled with a gas that has been separated by the gas chromatography apparatus and that has been flowing into the ionization chamber
40
through the sample inlet
70
. The photons and metastables then mix with and interact with the separated sample gas, cause electrons to be generated in the ionization chamber
40
, cause a current to form between the collector electrode
160
and the emitter electrode
170
, and allow for the concentration of the separated gas to be determined.
In order for the detector
10
to operate properly, the electrical discharges between the spark electrodes
90
are preferably chosen to be very stable. Instability in the discharges can cause serious deterioration of the analytical measurements being performed in the detector
10
. Such deteriorations can include shifts or oscillations in the analytical measurement. Hence, the detector
10
shown in
FIG. 1A
is generally attached to an electronic circuit
150
that attempts to drive the discharge while enhancing the stability of the discharge.
FIG. 1B
illustrates an electronic circuit
150
according to the related art that contains a resistor R, a first electrode
240
, a second electrode
250
, and a high voltage direct current (DC) power source
400
. However, the DC discharges driven by the circuit
150
illustrated in
FIG. 1B
are unstable due to uncontrolled wandering of the space charge present in the discharge area over time.
In order to enhance the stability of the discharges compared to the circuit
150
illustrated in
FIG. 1B
, related art circuits
150
such as the one illustrated in
FIG. 1C
have been employed and have been disclosed in U.S. Pat. No. 5,153,519 to Wentworth et. al., the contents of which are incorporated herein by reference. The circuit
150
illustrated in
FIG. 1C
includes a resistor R, a first electrode
240
and a second electrode
250
. According to such related art circuits
150
, short, periodic, DC pulses
410
are used to produce discharges across the spark electrodes
90
. However, the DC pulses generated by the circuit
150
illustrated in
FIG. 1C
results in discharge peak currents that are far greater than the average current.
Larger peak currents can cause deterioration and damage of the surface of the cathode spark electrode
90
, particularly when noble gases with larger atomic masses are employed as the surrounding gas. Hence, the high peak currents generated by the circuit
150
illustrated in
FIG. 1C
require large cathode areas and large cross-sectional discharge areas.
Such large-area configurations are disfavored because they do not enable high the gas atoms to achieve high linear velocities between the discharge chamber
30
and the ionization chamber
40
. Low linear velocities allow sample gas at high concentrations to diffuse into the discharge chamber
30
and quench the discharge. Hence, the detector's
10
sample dynamic range is not optimized, as further discussed in U.S. Pat. No. 6,037,179 to Abdel-Rahman, the contents of which are incorporated herein by reference.
To summarize, the electronic circuit
150
illustrated in FIG.
1
B and discussed above leads to instabilities in the DC discharges observed between the spark electrodes
90
. On the other hand, the electronic circuit
150
illustrated in
FIG. 1C
requires high peak currents to effectuate ionization, can cause damage to the electrodes
90
, and requires a large discharge cross-sectional area.
BRIEF SUMMARY OF THE INVENTION
According to one embodiment, an electronic circuit that includes a first electrode for electrical connection to an ionization detector system, a second electrode for electrical connection to an ionization detector system, and a transformer electrically connected to the first electrode and to the second electrode for creating a spark between the first electrode and the second electrode.
According to another embodiment, a method of generating an electrical discharge for an ionization detector system that includes providing a first electrode and a second electrode, each electrically connected to an ionization system, providing a transformer electrically connected to the first electrode and the second electrode, inputting a DC voltage into the primary portion of the transformer, and generating a discharge current between the first electrode and the second electrode.
REFERENCES:
patent: 3742475 (1973-06-01), Liebermann et al.
patent: 3781838 (1973-12-01), Primmer
patent: 4090308 (1978-05-01), Stuck
patent: 4446560 (1984-05-01), Gabor
patent: 4629992 (1986-12-01), Nudelmont
patent: 4698586 (1987-10-01), Roos et al.
patent: 4975648 (1990-12-01), Lawson et al.
patent: 5153519 (1992-10-01), Wentwort
Abdel-Rahman Mahmoud
Rhodes Robert P.
Agilent Technologie,s Inc.
Dole Timothy J.
Le N.
LandOfFree
Enhancing the stability of electrical discharges does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Enhancing the stability of electrical discharges, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Enhancing the stability of electrical discharges will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3286841