Current protection for photoionization detectors

Abstract

The present invention relates to a photoionization detector, which includes a sensor having at least a collector electrode and a ground electrode, a gas discharge lamp that ionizes molecules of interest to produce ionized molecules and electrons, and an amplifier connected to the collector electrode. Each of the collector electrode and the ground electrode includes a feedthrough pin; an inner trace surrounding the feedthrough pin; an outer trace surrounding the inner trace, wherein the outer trace on each electrode includes the same material; a channel between the inner trace and the outer trace, wherein the channel includes a material different from the outer trace and the inner trace; and a bridge connecting the outer trace to the inner trace. The ionized molecules can be collected by a bias electrode, and the electrons can be collected by the collector electrode.

Description

Technical Field

[0001] The present disclosure relates to an improved photoionization detector. More particularly, the present invention relates to a photoionization detector sensor having conductors with a unique geometry that reduces or prevents the flow of electric current. Background Art

[0002] A photoionization detector (PID) is a handheld, portable gas detector used to measure volatile organic compounds (VOCs) such as benzene and other organic gases by ionizing ambient gases and measuring the electrons generated. Photoionization detectors can produce instantaneous readings and can operate continuously, which makes them useful in monitoring health and safety in military, industrial and restricted work facilities. However, since PID sensors are capable of producing current levels that drop to the femtoampere range in proportion to the concentration of the measured ionized gas, the current produced in the presence of an electrolyte that bridges two conductors comprising different materials is a potential source of error in PID sensors and therefore limits the sensitivity of the detector. More specifically, when two electrodes, each comprising different metals having different electrical potentials, are bridged by an electrolyte, a current can be generated. When the current is generated, the current can produce errors in the readings by showing higher or lower readings.

[0003] Current technology focuses on cleanliness of materials to minimize the effects of stray currents and the formation of electrolytes in humid environments. However, better protection features are needed to provide protection from extraneous currents and permit more accurate and sensitive detectors that can be used in more extreme (ie, humid) environments. Summary of the invention

[0004] The present disclosure relates to a photoionization detector sensor having a conductor having a unique geometry that reduces or prevents electric current. In an illustrative but non-limiting example, the present disclosure provides a photoionization detector that may include: a sensor that includes at least a collector electrode and a ground electrode; a gas discharge lamp that ionizes molecules of interest to produce ionized molecules and electrons; and an amplifier that is connected to the collector electrode. The collector electrode and the ground electrode may each include a feedthrough pin, an inner trace surrounding the feedthrough pin, an outer trace surrounding the inner trace, a channel between the inner trace and the outer trace, and a bridge connecting the outer trace to the inner trace. The outer trace on each electrode may include the same material. The channel may include a different material than the outer trace and the inner trace. The ionized molecules may be collected by the bias electrode, and the electrons may be collected by the collector electrode.

[0005] In some cases, the channel may include a hydrophobic material. In addition, the hydrophobic material may be polytetrafluoroethylene. In some cases, the inner trace may include a gold-plated material. In some cases, the feedthrough pins are soldered in place. In addition, the solder may surround the feedthrough pins and cover at least a portion of the inner trace. In some cases, the inner trace, the outer trace, and the bridge may include the same material. In addition, the inner trace, the outer trace, and the bridge include gold-plated copper.

[0006] In some cases, the outer trace may be annular. In addition, the feedthrough pin may be centered within the outer trace. In some cases, the bridge on the collector electrode may be on a first side of the collector electrode, the ground electrode may be closest to a second side of the collector electrode, and the second side of the collector electrode may be opposite to the first side of the collector electrode. In addition, the bridge on the ground electrode may be on a first side of the ground electrode, the collector electrode may be closest to a second side of the ground electrode, and the second side of the ground electrode may be opposite to the first side of the ground electrode. In some cases, the ground electrode may be located between the bias electrode and the collector electrode.

[0007] In another illustrative but non-limiting example, the present disclosure provides a photoionization detector sensor, which may include at least two electrodes, the electrodes including a collector electrode and a ground electrode, wherein each electrode may include a feedthrough pin, an inner trace surrounding the feedthrough pin, an outer trace ring surrounding the inner trace, a channel between the inner trace and the outer trace ring, and a bridge connecting the outer trace ring to the inner trace. The outer trace ring on each electrode may include the same material. The channel may include a material different from the outer trace ring and the inner trace. The inner trace, the outer trace, and the bridge may include the same material. The feedthrough pin may be centered within the outer trace. The bridge on the collector electrode may be on the opposite side compared to the bridge on the ground electrode. In some cases, the photoionization detector sensor may further include a bias electrode. In some cases, the photoionization detector sensor may be combined with a gas discharge lamp that ionizes the molecules of interest to produce ionized molecules and electrons and an amplifier connected to the collector electrode. The ionized molecules may be collected by the bias electrode, and the electrons may be collected by the collector electrode.

[0008] In another illustrative but non-limiting example, the present disclosure provides a method of using a photoionization detector, which may include activating a gas discharge lamp and reading the output of an amplifier. The gas discharge lamp may ionize molecules of interest to produce ionized molecules and electrons. The ionized molecules may be collected by a bias electrode on the sensor. The electrons may be collected by a collector electrode on the sensor, where the collector electrode may be connected to an amplifier. The ground electrode and the collector electrode on the sensor may each include a feedthrough pin, an internal trace surrounding the feedthrough pin, an external trace surrounding the internal trace, a channel between the internal trace and the external trace, and a bridge connecting the external trace to the internal trace. The external trace on the electrode may include the same material. The channel may include a material different from the external trace and the internal trace. The channel may be configured to minimize current. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 Schematic diagram of a photoionization detector.

[0010] Figure 2a An exploded view of a prior art photoionization detector.

[0011] Figure 2b for Figure 2a A top view of a prior art photoionization detector sensor of a detector.

[0012] Figure 3 is a schematic top view of a photoionization detector sensor according to the present disclosure.

[0013] Figure 4 for Figure 3 Schematic bottom view of a photoionization detector sensor.

[0014] Figure 5 Schematic diagram of sensor electrodes of a prior art photoionization detector.

[0015] Figure 6 Schematic diagram of a sensor electrode of a photoionization detector according to the present disclosure. DETAILED DESCRIPTION

[0016] The present disclosure relates to a photoionization detector sensor (PID sensor) having a conductor having a unique geometry that reduces or prevents electric current. Various embodiments of the PID sensor will be described in detail with reference to the drawings, wherein similar reference numerals represent similar parts and assemblies throughout several views. Reference to various embodiments does not limit the scope of the PID sensor disclosed herein. In addition, any examples set forth in this specification are not intended to limit and only set forth some of the many possible embodiments for the PID sensor. It should be understood that various omissions and substitutions of equivalents are contemplated when circumstances dictate or the times dictate, but these omissions and substitutions are intended to cover applications or embodiments without departing from the spirit or scope of the present disclosure. In addition, it should be understood that the wording and terminology used herein are for descriptive purposes and should not be considered restrictive.

[0017] Figures 1 to 6 Various views showing examples of photoionization detectors according to the present disclosure. Figure 1 Schematic diagram of a photoionization detector. Figure 2a An exploded view of a prior art photoionization detector. Figure 2b for Figure 2a A top view of a prior art photoionization detector sensor of a detector. Figure 3 is a schematic top view of a photoionization detector sensor according to the present disclosure. Figure 4 for Figure 3 Schematic bottom view of a photoionization detector sensor. Figure 5 Schematic diagram of sensor electrodes of a prior art photoionization detector. Figure 6 Schematic diagram of a sensor electrode of a photoionization detector according to the present disclosure.

[0018] Some embodiments of the PID disclosed herein include a sensor having two or more electrodes, a gas discharge lamp, and an amplifier connected to one of the two or more electrodes. The two or more electrodes of the PID sensor may include a collector electrode, a bias electrode, a ground electrode, and combinations thereof (e.g., a collector electrode and a ground electrode). The bias electrode and the collector electrode may support an electrostatic field. The ground electrode may establish a low impedance path back to the power supply to facilitate operation of the device by intercepting current that may be generated between the bias electrode and the collector electrode (typically configured as a guard trace) and establishing a stable voltage to ground during operation.

[0019] like Figure 1As shown in , the gas discharge lamp 102 can ionize the molecules 104 of interest to produce ionized molecules 106 and electrons 108. More specifically, when the UV light source in the gas discharge lamp 102 is activated, the gas discharge lamp can ionize the ambient gas and produce ionized molecules 106 and electrons 108. The ionized molecules 106 can be collected by the bias electrode 110, and the electrons 108 can be collected by the collector electrode 112. The collector electrode 112 can be connected to an amplifier 114, which can be a high gain transimpedance amplifier that measures the electrons 108 generated from the ionized gas. When the gas 104 is ionized, the generated electrons 108 can be accelerated to the collector electrode 112 by the electrostatic field generated between the bias electrode 110 and the collector electrode 112. The results can be sent from the amplifier to a display / recorder 116 for viewing by a user.

[0020] Generally, a PID may have components contained within a cylindrical housing, such as Figure 2a More specifically, the cylindrical housing may include a sensor body 202 with a cover 204, wherein the sensor body and cover contain a gas discharge lamp 206 (with a UV light source), a sensor 208, a spacer 210, a filter cloth 212, and a filter 214. The components may be stacked on top of each other, such as Figure 2a As shown in , the gas discharge lamp 206 and the sensor 208 can be placed adjacent to each other.

[0021] As briefly mentioned above, the sensor may include two or more electrodes, such as, but not limited to, a bias electrode, a collector electrode, and a ground electrode. The electrodes 216, 218, 220 may be approximately circular and may be positioned in line with each other, such as Figure 2b In some embodiments, electrode 216 may be a bias electrode, electrode 218 may be a ground electrode, and electrode 220 may be a collector electrode. Figure 2a The PID and Figure 2b The details of the PID sensor in are prior art, but its components and layout can remain consistent with the PID and sensor described in this article. More specifically, as Figures 3 to 4 As shown in Figure 2b In the PID sensor 208 , the ground electrode 306 on the PID sensor 300 may be located between the bias electrode 302 and the collector electrode 304 .

[0022] like Figure 2a to 2b The prior art electrodes 216, 218 and 220 shown in FIG. Figure 5 The electrodes 502, 504 shown in the figure are approximately circular. Since the voltage difference between the bias electrode and the collector electrode can be tens or hundreds of volts, a third electrode, ie, a ground electrode, can be used to block surface conduction current that can be generated between the bias electrode and the collector electrode. Figure 5 Shown in the figure are the collector electrode 502 and the ground electrode 504. The collector electrode 502 and the ground electrode 504 may each include respective feed-through pins 506, 508 that are electrically connected. Materials commonly used in PIDs include gold plated features and tin-containing solder. The solder may be placed over the feed-through pins 506, 508 and may further cover portions of the internal traces 510, 512 so that the appearance of each electrode is that of an internal trace with solder on top.

[0023] Unfortunately, if the collector electrode and ground electrode are made of metals that are far apart in the potential series, it may cause the battery to become drained when bridged by a conductive medium. Because the materials used in PIDs include gold-plated features and tin-containing solders, these metals can generate an electrochemical voltage in the hundreds of millivolt range when bridged by a conductive medium. This voltage can appear between the ground electrode and the collector electrode, which can then be fed into a transimpedance amplifier. This stray voltage can drive the transimpedance amplifier in the positive or negative direction depending on which metal type is connected to the collector electrode and which type is connected to the ground electrode.

[0024] More specifically, and again with reference to Figure 5 In order to generate a voltage, if an electrolyte is present and there are two conductive materials with different electrical potentials (e.g., a first metal for the internal traces and a second metal for the solder), then moisture combined with surface contamination can produce a weak electrolyte that bridges the solder on one electrode to the internal traces on the second electrode, thus potentially producing a voltage that causes errors in the VOC measurement. However, if the electrolyte bridges two identical metals, no voltage will be generated because the two metals have the same electrical potential. Therefore, one solution to reduce errors in VOC measurements is to use only one metal type throughout the detector, or only metals that are galvanically close. Unfortunately, this may not always be achievable in actual designs.

[0025] Therefore, in the present disclosure, the geometry of the electrodes (i.e., conductors) has been designed to minimize the area in which metals with different electrochemical potentials can be bridged by the electrolyte. Figure 6As shown in , the area where solder is present on the electrodes 602, 604 (e.g., feedthrough pins 606, 608 and internal traces 610, 612) is surrounded by external traces 614, 616 made of a selected material (e.g., gold-plated copper). Thus, the electrode pattern confines the solder to the internal traces 610, 612 and feedthrough pins 606, 608. Thus, if or when electrolyte is generated between the electrodes 602, 604, it may first bridge the external traces 614, 616. As long as the surrounding external traces 614, 616 include the same material (or include materials that are galvanically close) for any set of electrodes 602, 604 on the sensor, any galvanic effects may be minimized even in the presence of a conductive electrolyte. Thus, if the solder is kept inside the internal traces 610, 612, the likelihood of mixed metals electrically bridging through the conductive electrolyte is reduced. Even if the electrolyte is always bridged to the inner traces 610, 612 and in contact with the solder, a voltage can be generated, but the voltage will be reduced due to the larger area of ​​the ring electrode relative to the solder area. This improved geometry and architecture eliminates the limitation of using only the same material or materials that are close in current to reduce errors in VOC measurements. In addition, it allows the PID sensor to have less variation in its measurement and also allows the production of a gain sensor with higher gain than previously possible. Finally, the improvement produces a sensor that is less sensitive to atmospheric changes and allows the use of PID in the environmental monitoring station market.

[0026] As mentioned above, the PID sensor may include at least two electrodes 602, 604, each having a feedthrough pin 606, 608, an inner trace 610, 612 surrounding each feedthrough pin, an outer trace 614, 616 surrounding each inner trace, a channel 618, 620 between each inner trace and each outer trace, and a bridge 622, 624 connecting each outer trace to each inner trace. The outer traces 614, 616 on both electrodes may include the same material. The channels 618, 620 may include a different material than the outer traces 614, 616 and the inner traces 610, 612.

[0027] More specifically, the at least two electrodes may be a collector electrode 602 and a ground electrode 604 positioned adjacent to each other, such as Figure 6 The electrodes 602, 604 may be approximately circular, and the feedthrough pins 606, 608 for each electrode may be approximately centered, as shown in FIG. Figure 6. The feed-through pins may include materials such as bronze, brass, copper, beryllium copper, stainless steel, etc., which may be plated with nickel, gold, silver, platinum, tin-lead, and tin-silver. The feed-through pins 606, 608 may be surrounded by internal traces 610, 612. The internal traces 610, 612 on each electrode 602, 604 may be circular and may include materials such as gold plating (e.g., gold-plated copper, silver-plated copper, tin-silver-plated copper, and tin-lead-plated copper). Each feed-through pin 606, 608 may be soldered in place in the center portion of the internal traces 610, 612. The solder may surround the feed-through pins 606, 608 and cover at least a portion of the corresponding internal traces 610, 612.

[0028] Surrounding each inner trace 610, 612 of the electrodes 602, 604 may be a channel 618, 620. This channel 618, 620 may be circular or annular and may include a hydrophobic material such as, but not limited to, polytetrafluoroethylene (i.e., Teflon). In some cases, the channel 618, 620 may include the same material as the sensor plate 626, to which the sensor material is all connected. Thus, in manufacturing, the channel may simply be a gap between the inner traces 610, 612 and the outer traces 614, 616. In other cases, the channel may be additional material placed onto the sensor plate 626 and between the inner traces 610, 612 and the outer traces 614, 616.

[0029] Surrounding each channel 618, 620 of the electrodes 602, 604 may be an outer trace 614, 616. The outer traces 614, 616 may be circular or annular and may include the same material as the inner traces 610, 612, such as gold-plated material (e.g., gold-plated copper (e.g., gold-plated copper, silver-plated copper, tin-silver-plated copper, and tin-lead-plated copper). The thickness of the outer traces may be similar to the thickness of the exposed portions of the inner traces 610, 612, such as Figure 6 Alternatively, the outer traces may be thinner or thicker than the inner traces 610, 612. Like the inner traces 612, 612, the feedthrough pins 606, 608 may be centered on the outer traces 614, 616. Thus, in one embodiment, the inner traces 610, 612, the channels 618, 620, and the outer traces 622, 624 may be a series of loops centered on each other, such as Figure 6 , and the feedthrough pins 606, 608 can be centered within this series of rings. Alternatively, the inner traces, channels, and outer traces can be solid circular pieces centered and stacked on top of each other, with the feedthrough pins penetrating all layers.

[0030] In general, the larger the space between all electrodes, the better, however, practical design constraints will limit what can be achieved. The relative size of the outer traces and the inner traces and the channel therebetween can affect the effectiveness of the current blocking pattern. Since the solder on the outer ring will connect the mixed metals and will reduce the effectiveness of the current blocking pattern, the channel can be wide enough to easily solder the feed-through pins without obtaining solder on the outer ring. The bridge from the inner trace to the outer trace (which will be explained in more detail below) should be as narrow as permitted by the manufacturing process that produces the pattern. The radius of the inner trace only needs to be large enough to allow good solder attachment to the feed-through pins.

[0031] The bridge 622, 624 may connect the inner trace 610, 612 to the outer trace 614, 616 on the electrode 602, 604. The bridge 622, 624 may be a straight section of material connected to the inner trace 610, 612 on a first end and to the outer trace 614, 616 on a second end. The bridge may have the same width as the inner trace 610, 612, the same width as the outer trace 614, 616, or a different width than the inner trace or the outer trace. In some embodiments, the bridge 622, 624 includes the same material as the inner trace 610, 612 and the outer trace 614, 616 (e.g., gold-plated copper, silver-plated copper, tin-silver-plated copper, and tin-lead-plated copper). In addition, the inner trace 610, 612, the outer trace 614, 616, and the bridge 622, 624 may all be on the same horizontal plane so that they all lie relatively flat on the sensor board 626. The orientation of the bridges 622 , 624 on the collector electrode 602 and the ground electrode 604 , respectively, may be symmetrical, mirrored, or any other configuration.

[0032] More specifically, in some embodiments, each electrode 602, 604 may have at least a first side and a second side. The bridge 622 on the collector electrode 602 may be on the first side of the collector electrode, the ground electrode 604 may be closest to the second side of the collector electrode, and the second side of the collector electrode may be opposite to the first side of the collector electrode. In addition, the bridge 624 on the ground electrode 604 may be on the first side of the ground electrode, the collector electrode 602 may be closest to the second side of the ground electrode, and the second side of the ground electrode may be opposite to the first side of the ground electrode. Figure 6604, where the first side of the collector electrode 602 is the left side and the first side of the ground electrode 604 is the right side (i.e., the bridges are on opposite sides). However, the electrodes are not limited to this left-right configuration, and in some cases, the bridges may additionally be mirrored on opposite ends (e.g., top and bottom, right and left, or opposite corners), or the bridges may all be on the same side such that the bridges are symmetrical about their respective electrodes (e.g., both bridges are on the top, left, right, or bottom). In other embodiments, the bridges may be randomly placed such that they do not have an obvious symmetry or mirrored configuration relative to each other.

[0033] However, in the prior art, the inner traces have connection lines 514, 516, in the present disclosure, the connection lines 628, 630 are actually paired with the outer traces 614, 616 for each electrode 602, 604. In some cases, the connection lines can be a continuation of the corresponding bridge, such as Figure 4 In other cases, the connecting wires may be separated from the bridges on the electrodes, such as Figure 4 For example, one or more of the connecting lines 628, 630 may be positioned at 90 degrees to the bridges 622, 624, as shown in FIG. Figure 6 As shown in .

[0034] In use, a photoionization detector with improved geometry and architecture for sensor electrodes can be used by activating a gas discharge lamp and reading the output of an amplifier. The gas discharge lamp may have a UV light source and may ionize molecules of interest to produce ionized molecules and electrons. The ionized molecules may be collected by a bias electrode 302 on the sensor 300, and the electrons may be collected by a collector electrode 304 on the sensor, which may be further connected to an amplifier. A ground electrode 306 on the sensor may be located between the bias electrode 302 and the collector electrode 304. The collector electrode 304 and the ground electrode 306 may each include a feedthrough pin 308, 310, an inner trace 312, 314 surrounding the feedthrough pin, an outer trace 320, 322 surrounding the inner trace, a channel 316, 318 between the inner trace and the outer trace, and a bridge 324, 326 connecting the outer trace to the inner trace. In some embodiments, the outer traces 320, 322 on the two electrodes may include the same material. Additionally, the channels 316 , 318 may include a different material than the outer traces 320 , 322 and the inner traces 312 , 314 .

[0035] The various embodiments described above are provided by way of illustration only and should not be construed as limiting the claims appended hereto. Those skilled in the art will readily appreciate that various modifications and changes may be made without departing from the true spirit and scope of the appended claims and the exemplary embodiments and applications shown and described herein.

Claims

1. A photoionization detector, comprising: A sensor comprising at least a collector electrode and a ground electrode, wherein both the collector electrode and the ground electrode comprise Feedthrough pin, The internal trace surrounding the feedthrough pin, an outer trace surrounding the inner trace, wherein the outer trace on each electrode comprises the same material, a channel between the inner trace and the outer trace, wherein the channel comprises a different material than the outer trace and the inner trace, and a bridge connecting the outer trace to the inner trace; a gas discharge lamp that ionizes molecules of interest to produce ionized molecules and electrons, wherein the ionized molecules can be collected by the bias electrode and the electrons can be collected by the collector electrode; as well as amplifier, which is connected to the collector electrode.

2. The photoionization detector of claim 1, wherein the channel comprises a hydrophobic material. The photoionization detector according to claim 2 , wherein the hydrophobic material is polytetrafluoroethylene.

4. The photoionization detector of claim 1, wherein the internal traces comprise a gold plated material.

5. The photoionization detector of claim 1, wherein the feedthrough pins are soldered in place.

6. The photoionization detector of claim 5, wherein solder surrounds the feedthrough pin and covers at least a portion of the internal trace.

7. The photoionization detector of claim 1, wherein the inner trace, the outer trace, and the bridge comprise the same material.

8. The photoionization detector of claim 7, wherein the inner trace, the outer trace, and the bridge comprise gold-plated copper.

9. The photoionization detector of claim 1, wherein the outer trace is annular.

10. The photoionization detector of claim 9, wherein the feedthrough pin is centered within the external trace.

11. The photoionization detector according to claim 1, wherein the bridge on the collector electrode is on a first side of the collector electrode, The ground electrode is closest to the second side of the collector electrode, and The second side of the collector electrode is opposite to the first side of the collector electrode.

12. The photoionization detector according to claim 11, wherein the bridge on the ground electrode is on a first side of the ground electrode, The collector electrode is closest to the second side of the ground electrode, and The second side of the ground electrode is opposite to the first side of the ground electrode.

13. The photoionization detector of claim 1, wherein the ground electrode is located between the bias electrode and the collector electrode.

14. A photoionization detector sensor, the photoionization detector sensor comprising: At least two electrodes, including a collector electrode and a ground electrode, wherein each electrode comprises Feedthrough pin, The internal trace surrounding the feedthrough pin, an outer trace ring surrounding the inner trace, wherein the outer trace ring on each electrode comprises the same material, a channel between the inner trace and the outer trace loop, wherein the channel comprises a different material than the outer trace loop and the inner trace, and a bridge connecting the outer trace loop to the inner trace; wherein the inner trace, the outer trace, and the bridge comprise the same material, wherein the feedthrough pin is centered within the external trace, and Wherein the bridge on the collector electrode is on an opposite side compared to the bridge on the ground electrode.

15. The photoionization detector sensor of claim 14, further comprising a bias electrode.

16. The photoionization detector sensor of claim 15 in combination with: a gas discharge lamp that ionizes molecules of interest to produce ionized molecules and electrons, wherein the ionized molecules can be collected by the bias electrode and the electrons can be collected by the collector electrode; and amplifier, which is connected to the collector electrode.

17. A method of using a photoionization detector, the method comprising: Activate the gas discharge lamp, which The gas discharge lamp ionizes the molecules of interest to produce ionized molecules and electrons, The ionized molecules can be collected by biased electrodes on the sensor. The electrons can be collected by a collector electrode on the sensor, wherein the collector electrode is connected to an amplifier; and Reading the output of the amplifier, The ground electrode and the collector electrode on the sensor each include Feedthrough pin, The internal trace surrounding the feedthrough pin, an outer trace surrounding the inner trace, wherein the outer trace on the electrode comprises the same material, a channel between the inner trace and the outer trace, wherein the channel comprises a different material than the outer trace and the inner trace, and a bridge connecting the outer trace to the inner trace, and The channel is configured to minimize current flow.

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