Patent Description:
Applicant has identified many technical challenges and difficulties associated with the operation of PID sensors utilizing FAIMS techniques. Through applied effort, ingenuity, and innovation, Applicant has solved problems related to the structure and operation of PID sensors by developing solutions embodied in the present disclosure, which are described in detail below.

<CIT> discloses that a system for detecting particles in a gas stream comprises a Faraday collector separating charged particles into positive and negative streams to be detected. The Faraday collector includes a plurality of interdigitated wires, with a first plurality of wires charged with a positive potential and a second plurality of wires charged with a negative potential to separate particles in the gas stream into the positive and negative streams.

<CIT> discloses an ion-mobility analyser comprising a plurality of axially segmented upper electrodes, a plurality of axially segmented lower electrodes, a first plurality of axially segmented intermediate electrodes and a second plurality of axially segmented intermediate electrodes which together define an ion pathway. An asymmetric voltage waveform is applied to the upper electrodes and a DC compensating voltage is applied to the lower electrodes in order to separate ions in a vertical radial direction according to their rate of change of ion mobility with electric field strength. At the same time, a DC axial voltage gradient is maintained along the axial length of the analyser in order to separate ions axially according to their ion mobility.

<CIT> discloses that an ion mobility spectrometer is described having an ion filter in the form of at least one ion channel having a plurality of electrodes. A time-varying electric potential applied to the conductive layers allows the filler to selectively admit ion species. The electric potential has a drive and a transverse component, and in preferred embodiments each of the electrodes is involved in generating a component of both the drive and transverse fields. The device may be used without a drift gas flow, Microfabrication techniques are described for producing microscale spectrometers, as are various uses of the spectrometer.

Various embodiments are directed to an example method as defined in claim <NUM>, apparatus as defined in claim <NUM>, and computer program product as defined in claim <NUM> for utilizing a PID sensor, leveraging differences in high-field and low-field ion mobility of target VOCs, to detect VOCs in a gas. The present invention is defined in the independent claims, to which reference should now be made. Advantageous features are set out in the sub claims.

The PID sensor for detecting VOCs in a gas comprises a processing device and a detecting region. The detecting region further comprises a first interdigital pole disposed within the detecting region and electrically connected to a separation voltage source, a second interdigital pole disposed within the detecting region and electrically connected to a switch, and an ionization device configured to interact with the gas within the detecting region creating a plurality of ionized gas molecules, wherein the switch alternates the connection of the second interdigital pole between a compensation voltage source and the processing device. Further, the processing device determines a VOC value representative of a number of volatile organic compounds in the gas based at least in part on a number of ionized gas molecules that contact the second interdigital pole while the second interdigital pole is electrically connected to the processing device.

In some embodiments, the PID VOC sensor may further comprise a housing comprising a base, wherein the processing device is attached to the housing at or near the base, and a housing wall protruding from the base forming an enclosed perimeter around an interior cavity and defining an opening opposite the base. In some embodiments, the switch may be positioned in the interior cavity and attached to the housing, and the ionization device may be disposed proximate the base and directed toward the opening. The PID VOC sensor may further comprise a cap detachably connected to the housing wall, substantially covering the opening and further comprising a vent, wherein the gas enters the housing through the vent, wherein the detecting region may be positioned inside the interior cavity of the housing between the vent in the cap of the housing and the ionization device. The PID VOC sensor may further comprise a first electrical connector disposed on the exterior of the housing and providing electrical connectivity from the separation voltage source to the interior cavity of the housing and a second electrical connector disposed on the exterior of the housing and providing electrical connectivity from the compensation voltage source to the interior cavity of the housing. In some embodiments, the first interdigital pole of the detecting region may be electrically connected to the first electrical connector, and the switch may be positioned inside the interior cavity of the housing and alternate an electrical connection from the second electrical connector and the processing device to the second interdigital pole of the detecting region.

In some embodiments, the first and second interdigital poles each comprise a plurality of comb-like conducting prongs, wherein the prongs of the first interdigital pole may be directed toward the prongs of the second interdigital pole, and wherein the second interdigital pole may offset from the first interdigital pole such that the prongs of the first interdigital pole occupy a space between the prongs of the second interdigital pole.

In some embodiments, the PID VOC sensor may operate in at least three time phases, an ionization phase wherein gas molecules of the gas are exposed to the ionization device, a separation phase wherein a separation voltage is applied to the first interdigital pole, and a detection phase wherein the switch is positioned to electrically connect the second interdigital pole to the processing device.

In some embodiments, the ionization phase and the separation phase may substantially overlap.

In some embodiments, the ionization device may be an ultraviolet lamp projecting into the detecting region, and gas molecules with an ionization potential lower than ionization energy of the UV light may be ionized.

In some embodiments, the ultraviolet lamp may be substantially on during the ionization phase and substantially off during the detection phase.

In some embodiments, the switch may be a single pole double throw switch having an input side with a single input connector and an output side having a first output connector and a second output connector, wherein the single input connector is electrically connected to the second interdigital pole, the first output connector is electrically connected to the compensation voltage source, and the second output connector is electrically connected to the processing device.

In some embodiments, the detection phase may be defined by the switch providing an electrical connection between the second interdigital pole and the processing device, a first constant DC voltage supplied to the first interdigital pole and a second constant DC voltage is supplied to the second interdigital pole, and the ionization device being disabled.

In some embodiments, the separation voltage source may provide an alternating current to the first interdigital pole during the separation phase and otherwise supply a constant direct current voltage to the first interdigital pole.

In some embodiments, the compensation voltage source may be a direct current voltage.

A method for detecting volatile organic compounds (VOCs) in a gas diffused into a detecting region of a VOC sensor is further provided. The method comprises executing an ionization phase comprising, exposing the gas to an ionization device creating a plurality of ionized gas molecules. The method further comprises executing a separation phase comprising, supplying a separation voltage to a first interdigital pole disposed within the detecting region and electrically connected to a separation voltage source, and supplying a compensation voltage to a second interdigital pole disposed within the detecting region and electrically connected to a compensation voltage source through a switch. The method further comprises disabling the ionization device upon completion of the ionization phase. The method further comprises executing a detection phase comprising, switching the switch to electrically connect the second interdigital pole to a processing device, supplying a first direct current voltage to the first interdigital pole and supplying a second direct current voltage to the second interdigital pole, and determining a VOC value representative of a number of volatile organic compounds in the gas based at least in part on a number of ionized gas molecules that contact the second interdigital pole while the second interdigital pole is electrically connected to the processing device.

In some embodiments, the first and second interdigital poles may each comprise a plurality of comb-like conducting prongs, wherein the prongs of the first interdigital pole are directed toward the prongs of the second interdigital pole, and wherein the second interdigital pole is offset from the first interdigital pole such that the prongs of the first interdigital pole occupy a space between the prongs of the second interdigital pole.

In some embodiments, the ionization device may be an ultraviolet (UV) lamp projecting into the detecting region, and gas molecules with an ionization potential lower than UV light may be ionized.

In some embodiments, the switch may be a single pole double throw switch having an input side with a single input connector and an output side having a first output connector and a second output connector, and the single input connector is electrically connected to the second interdigital pole, the first output connector is electrically connected to the compensation voltage source, and the second output connector is electrically connected to the processing device.

In some embodiments, the separation voltage source may provide an alternating current to the first interdigital pole during the separation phase and the separation voltage source may otherwise supply a constant direct current voltage to the first interdigital pole.

In some embodiments, the detection phase may further comprise altering the second direct current voltage that is supplied to the second interdigital pole.

A computer program product for detecting volatile organic compounds (VOCs) in a gas diffused into a detecting region of a VOC sensor is also provided. The computer program comprises at least one non-transitory computer-readable storage medium having computer-readable program code portions stored therein, the computer-readable program code portions comprising an executable portion configured to execute an ionization phase comprising enabling an ionization device and creating a plurality of ionized gas molecules. The executable portion is further configured to execute a separation phase comprising causing a separation voltage to be supplied to a first interdigital pole disposed within the detecting region and electrically connected to a separation voltage source, and causing a compensation voltage to be supplied to a second interdigital pole disposed within the detecting region and electrically connected to a compensation voltage source through a switch. The executable portion is further configured to disable the ionization device upon completion of the ionization phase. In addition, the executable portion is further configured to execute a detection phase comprising toggling the switch to electrically connect the second interdigital pole to a processing device, and causing a first direct current voltage to be supplied to the first interdigital pole and cause a second direct current voltage to be supplied to the second interdigital pole. The executable portion further configured to determine a VOC value representative of a number of volatile organic compounds in the gas based at least in part on a number of ionized gas molecules that contact the second interdigital pole while the second interdigital pole is electrically connected to the processing device.

Reference will now be made to the accompanying drawings. The components illustrated in the figures may or may not be present in certain embodiments described herein. Some embodiments may include fewer (or more) components than those shown in the figures in accordance with an example embodiment of the present disclosure.

Example embodiments will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the inventions of the disclosure are shown. Indeed, embodiments of the disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements.

Various example embodiments address technical problems associated with detecting volatile organic compounds (VOCs) in a gas. As understood by those of skill in the field to which the present disclosure pertains, there are numerous example scenarios in which a user may need to a detect the presence and/or concentration of VOCs in a gas (e.g., air).

Volatile organic compounds are substances associated with a low boiling point at room temperature resulting in molecules that are susceptible to ready release into the surrounding air. VOCs released into the air can be dangerous to human health or to the environment. For example, substances such as solvents and paint thinners, as well as vapors associated with fuel and oil may release VOCs into the surrounding environment creating smog and generating ozone. VOCs inhaled by humans and animals can have adverse health effects such as causing irritation, allergies, damage to organs and the nervous system, and even cancer. In addition, a detectable amount of VOCs may be released from drugs, explosives, and chemical weapons, indicating the presence of these objects in a particular environment.

Photoionization detector (PID) sensors may detect the presence of VOCs through a technique known as ion mobility spectrometry (IMS). IMS exploits the differing mobility of ionized molecules in a gas, including VOCs, to separate a targeted VOC from other ionized and non-ionized molecules. Once separated, a device utilizing IMS techniques may measure the presence of ionized modules based on the voltage produced on an electrical conductor. High-field asymmetric-waveform ion-mobility spectrometry, or FAIMS, is another technique that takes advantage of the differing ion mobilities to separate ionized gas molecules. Specifically, FAIMS leverages the property present in many ionized molecules that the mobility of the ionized molecule is different in the presence of a high electric field versus a low electric field. PID detectors utilizing FAIMS techniques may pass the gas potentially containing VOCs through a varying electric field. Ionized molecules that are not targeted will drift toward one or the other of the electrodes where they will be neutralized upon contact. While targeted molecules will move through the separation region without impacting either electrode. Molecules that pass through the separation region without being neutralized will pass into the detecting region where the number of remaining molecules will be detected in the detecting region based on the electrical voltage produced by their presence. Detecting the presence of VOCs in gasses can be an important tool in identifying air-born molecules that are harmful to humans and/or the environment, or even indicate the presence of dangerous and/or illegal items.

However, many traditional VOC detectors can be too large or cumbersome for intended mobile uses. Many VOC detectors require a carrier gas to drive the potential VOC containing gas through a separating region. This type of setup generally requires a flow meter and pump which may add to the overall size and complexity of the device. In addition, VOC detectors utilizing FAIMS techniques require multiple sets of electrodes to separate the ionized molecules and separately detect the separated target molecules, further adding to the size and complexity of the device. Further, traditional VOC detectors must expose the gas to an ionization source in a separate region, resulting in loss of ions even before entering the separating region. Finally, VOC detectors generally require an ionization source which is constantly enabled, decreasing the project life of the device.

The various example embodiments described herein utilize various techniques to improve the detection of VOCs in a gas using FAIMS techniques. For example, in some embodiments, a PID VOC sensor in accordance with the present disclosure may utilize a single set of electrodes to perform separation and detection. In addition, ionization, separation, and detection may all occur in the same physical region. Confining these phases of VOC detection to the same region may be made possible, in some embodiments, by attaching at least one of the electrodes to a switch, which alternates power between a compensation voltage source and a processing device. This allows the electrode to fulfill the role of separating the ionized molecules according to mobility when connected to the compensation voltage source and detecting/counting the target molecules when switched to the processing device. By confining each of these steps to the same physical region, the overall architecture of the PID VOC sensor may be simplified and the overall size reduced. Further, ionizing the gas molecules in the same physical location as the separating and detecting region reduces the number of ions lost, improving the overall accuracy of the sensor.

In addition, in some embodiments disclosed herein, switching at least one electrode between a compensation voltage source and a processing device allows the PID VOC sensor described herein to switch on and off the ionization source. In embodiments wherein the ionization source is a UV lamp, or similar device, switching off the ionization source during the detection phase prolongs the life of the device.

As a result of the herein described example embodiments and in some examples, the effectiveness of a PID VOC sensor in detecting target VOC materials may be greatly improved. In addition, the size and overall complexity of the architecture may be reduced, facilitating use of the PID VOC sensor in diverse mobile and fixed embodiments.

<FIG> illustrates an example prior art process for VOC detection using a PID sensor utilizing FAIMS techniques. As shown in <FIG>, the example prior art PID VOC sensor utilizes a process that includes a separation region <NUM> followed by a detection region <NUM>. The separation region <NUM> includes two electrodes (e.g., first electrode <NUM> and second electrode <NUM>), substantially parallel to each other and generating an electric field between them according to a waveform similar to separation radio frequency (RF) waveform <NUM>. In addition, an ionization source <NUM> interacts with the gas molecules prior to entering the separation region <NUM>, ionizing gas molecules with an ionization potential less than the energy emitted by the ionization source <NUM>. After exposure to the ionization source <NUM>, the ionized gas flows through the separation region <NUM>, from the ionization source <NUM> toward the detection region <NUM>, between the first electrode <NUM> and the second electrode <NUM>. The detection region <NUM> includes a second set of one or more electrodes (e.g., detecting electrode <NUM>) which determine the presence of ionized molecules (e.g., detected ion <NUM>) based on the electric voltage generated by the presence of the ionized particles. Ionized particles (e.g., separated ion <NUM> and separated ion <NUM>) which drift toward the electrodes in the separation region <NUM> and contact one of the electrodes (e.g., first electrode <NUM> and second electrode <NUM>) are neutralized and not detected.

As shown in <FIG>, the example prior art process for VOC detection using a PID sensor utilizing FAIMS techniques includes a separation region <NUM> physically distinct from the detection region <NUM>. In order to separate target ions (e.g., detected ion <NUM>) the ionized gas most flow through the separation region <NUM> at a regulated rate. This regulated flow of gas often requires additional equipment, such as a flow meter and/or pump. As such, gas particles are exposed to the ionization source <NUM> previous to entering the separation region <NUM>. Exposure to the ionization source <NUM> previous to entering the separation region <NUM>, and subsequent travel through the separation region <NUM> may result in ion loss due to diffusion, adversely affecting the detection of VOCs. In addition, physically separate separation regions <NUM> and detection regions <NUM> require an additional electrode, or electrodes. A first set of electrodes (e.g., first electrode <NUM> and second electrode <NUM>), as shown in <FIG>, are required to oscillate the electric field according to separation RF waveform <NUM> or a similar waveform, while a second set of electrodes (e.g., detecting electrode <NUM>) are required to accurately determine the presence of VOCs due to the electric voltage generated by the presence of ionized molecules (e.g., detected ion <NUM>).

Referring now to <FIG>, an example interdigital pole conducting component <NUM> is provided. The depicted example interdigital pole conducting component <NUM> of <FIG>, shows a first interdigital pole <NUM> comprising a first conducting pad <NUM> and a first plurality of conducting prongs <NUM> projecting out from the first conducting pad <NUM> in parallel, comb-like prongs. Additionally, a second interdigital pole <NUM> is further provided comprising a second conducting pad <NUM> and a second plurality of conducting prongs <NUM> projecting out from the second conducting pad <NUM> also in parallel, comb-like prongs. The first interdigital pole <NUM> is positioned such that the first plurality of conducting prongs <NUM> are extending from the first conducting pad <NUM>, towards the second interdigital pole <NUM> while the second plurality of conducting prongs <NUM> are extending from the second conducting pad <NUM> toward the first interdigital pole <NUM>. The second interdigital pole <NUM> is positioned such that the second plurality of conducting prongs <NUM> are offset from the first plurality of conducting prongs <NUM> and substantially parallel to the first plurality of conducting prongs <NUM>. Further, the first interdigital pole <NUM> and the second interdigital pole <NUM> are positioned such that the furthest extent of the first plurality of conducting prongs <NUM> extend past the furthest extent of the second plurality of conducting prongs <NUM>, forming narrow gaps (e.g., electric field region <NUM>) between the first set of conducting prongs <NUM> and the second set of conducting prongs <NUM>. In operation, an electric charge may be applied to the first conducting pad <NUM> of the first interdigital pole <NUM> and the second conducting pad <NUM> of the second interdigital pole <NUM> generating an electric field in the plurality of electric field regions <NUM>.

As depicted in <FIG>, the example interdigital pole conducting component <NUM> includes a plurality of interdigital poles (e.g., first interdigital pole <NUM> and second interdigital pole <NUM>). An interdigital pole may be any conducting or semi-conducting material, or a combination of conducting, semi-conducting, and insulating materials, such that when an electric charge is applied to a conducting pad (e.g., first conducting pad <NUM> and second conducting pad <NUM>), the electric charge is transmitted on or along each of the plurality of conducting prongs (e.g., first plurality of conducting prongs <NUM> and second plurality of conducting prongs <NUM>).

A PID sensor implementing FAIMS techniques separates ions based on the ion mobility in differing electric fields. An ions mobility (K) is the average velocity with which a given ion drifts when influenced by an electric field. Ions generated from different compounds may each have a different mobility when exposed to an electric field, meaning different ions will travel farther when exposed to the same electric field for the same amount of time. In addition, an ion may have a different mobility based on the intensity of an electric field (e.g., Kh for a high electric field Eh, and Kl for a low electric field El such that Kh ≠ Kl). For example, an ion may travel a farther distance when influenced by a high electric field then when influenced by a low electric field, even when the duration of exposure to each electric field (e.g., th for the high electric field and tl for the low electric field) is adjusted such that the product of the magnitude of the electric field and the duration of that electric field are equal (e.g., Ehth = Eltl).

Common FAIMS implementations will apply an asymmetric waveform (e.g., separation RF waveform <NUM>), or separation voltage, to a first electrode, for example, first interdigital pole <NUM>. A separation voltage, may be composed of a repeating pattern, including a high voltage component lasting for a short period of time and a lower voltage component of opposing polarity lasting for a longer period of time. Thus, when the separation voltage is applied to a first electrode, for example, first interdigital pole <NUM>, VOCs will drift either toward or away from the interdigital pole based on the ratio of the mobility of the ion in the presence of a high electric field to the mobility of the ion in the presence of a low electric field (Kh / Kl). However, PID sensors utilizing FAIMS techniques may also apply a compensation voltage, or direct current (DC) voltage, to a second electrode, for example, interdigital pole <NUM>. A compensation voltage is calculated to correct the drift of targeted ions. The compensation voltage allows the targeted ions to oscillate back and forth in the space between the two electrodes without contacting either one, while the non-targeted ions drift toward one or the other electrode. The compensation voltage may be updated or changed throughout the separation process, or in subsequent separation processes to target VOCs with different mobility properties.

Thus, by applying a separation voltage to the first interdigital pole <NUM> and a compensation voltage to the second interdigital pole <NUM>, an oscillating electric field is generated in the electric field region <NUM>. This oscillating electric field, in the space between the first interdigital pole <NUM> and the second interdigital pole <NUM>, causes the targeted ions to remain in the space between the interdigital poles, while the non-targeted ions drift toward and contact one of the interdigital poles. By applying this technique, the targeted ions alone remain in the electric field region <NUM>.

Referring now to <FIG>, an example interdigital pole component <NUM> is depicted. As depicted in <FIG>, the example interdigital pole component <NUM> includes an interdigital pole conducting component <NUM>.

The interdigital pole conducting component <NUM> is placed within an interdigital pole holder <NUM>. The interdigital pole holder <NUM> includes an opening (e.g., interdigital poles cutout <NUM>) substantially similar to the shape of the interdigital pole conducting component <NUM>, receiving the interdigital pole conducting component <NUM> in a position which allows the interdigital poles to receive ion exposure from an ionization source <NUM> and receive the input gas from an exterior environment.

As further depicted in <FIG>, the interdigital pole holder <NUM> and the interdigital pole conducting component <NUM> are disposed between the interdigital pole top cover <NUM> and the interdigital pole bottom cover <NUM> such that the interdigital pole conducting component <NUM> is forced into the interdigital poles cutout <NUM> in the interdigital pole holder <NUM>. The interdigital pole top cover <NUM> further includes an opening (e.g., top cover opening <NUM>) which allows gas to flow in and enter the electric field region <NUM> of the interdigital pole conducting component <NUM>.

The interdigital pole bottom cover <NUM> further includes an interdigital poles exposure window <NUM>, allowing an ion source such as a ultraviolet (UV) lamp to ionize the incoming gas. In addition, the interdigital pole bottom cover <NUM> includes electrical connecter openings <NUM>. The electrical connector openings allow electrical conductors, such as pogo pins, to pass through the interdigital pole bottom cover <NUM> and contact each of the interdigital poles at first conducting pad <NUM> and second conducting pad <NUM>.

Each of the interdigital pole bottom cover <NUM>, interdigital pole holder <NUM>, and interdigital pole top cover <NUM> further include screw holes <NUM> through which screws (e.g., screws <NUM>) pass. In operation, the screws <NUM> align the openings in the surrounding covers with the interdigital pole conducting component <NUM>. Further, the screws <NUM> compress the interdigital pole conducting component <NUM> between the interdigital pole bottom cover <NUM> and interdigital pole top cover <NUM> holding the interdigital pole conducting component <NUM> in the interdigital poles cutout <NUM>.

As further depicted in <FIG>, the example interdigital pole component <NUM> includes an interdigital pole housing <NUM> comprising an interdigital pole housing opening <NUM>. The interdigital pole housing <NUM> further includes screw receivers <NUM> allowing the screws <NUM> to attach to the interdigital pole housing <NUM>. Once attached, the screws <NUM> work to fasten the interdigital pole bottom cover <NUM>, the interdigital pole holder <NUM> with the interdigital pole conducting component <NUM> disposed therein, and the interdigital pole top cover <NUM> against the interdigital pole housing <NUM> and within the cavity created by the interdigital pole housing <NUM>. The interdigital pole housing opening <NUM> allows gas to disperse into the interdigital pole component <NUM> and into the electric field region <NUM> of the interdigital pole conducting component <NUM>.

Referring now to <FIG>, a cross-section of an example PID VOC sensor <NUM> is provided. As shown in <FIG>, the example PID VOC sensor <NUM> includes a PID detecting region <NUM> wherein a first interdigital pole <NUM> and a second interdigital pole <NUM> are disposed. Further contained in the PID detecting region <NUM> is a plurality of ionized molecules <NUM> and a plurality of non-ionized molecules <NUM>. From one side of the PID VOC sensor <NUM>, input gas <NUM> is diffused into the PID detecting region <NUM>. From the opposite side of the PID VOC sensor <NUM>, an ionization source <NUM> is disposed and directed to the PID detecting region <NUM> to ionize molecules from the input gas <NUM>. In addition, a separation voltage source <NUM> is electrically connected to the first interdigital pole <NUM>. A switch <NUM> is electrically connected to the second interdigital pole <NUM>, providing selectable electrical connectivity to a compensation voltage source <NUM> and a processing device <NUM>.

As depicted in <FIG>, the example PID VOC sensor <NUM> includes a PID detecting region <NUM>. As described herein, the PID detecting region <NUM> is utilized to ionize, separate, and detect targeted VOC molecules. The PID detecting region <NUM> depicted in <FIG> includes an opening allowing input gas <NUM> to diffuse into the PID detecting region <NUM>. The input gas <NUM> may be any gas, vapor, or other similar matter in which the detection of VOCs is desired. The input gas <NUM> may be received from the surrounding environment, from a person's or animal's breath, from hazardous areas, from a contained gas source, from fumes emanating from a fuel, solvent, or other object, the environment in an industrial or chemical plant, and/or from other similar sources of gas which may contain VOCs. In order for detection to occur, the gas must diffuse into the PID detecting region <NUM> for ionization, separation, and detection.

As further depicted in <FIG>, the example PID VOC sensor <NUM> includes an ionization source <NUM> which is directed at the PID detecting region <NUM> and interacts with molecules of the input gas <NUM>. An ionization source <NUM>, may be any component, device, or substance configured to break the chemical bonds of VOCs such that ionized molecules result. The ionization phase of the detection process is characterized by the enabling of the ionization source <NUM> and the interaction of the emitted ionization source <NUM> photons with the input gas <NUM> molecules. A VOC molecule will be ionized only if the ionization potential of the particular VOC molecule is less that the energy emitted by the ionization source <NUM>. In some embodiments, a UV lamp may be used as an ionization source <NUM>. A UV lamp may emit photons of different energy based on the gas within the photon lamp. For example, an ionization lamp may contain Krypton, Xenon, Argon, etc. Each of these sources, when heated up, may output photons of different energy, thus ionizing a different range of potentially detectable VOCs. The ionization source <NUM> may be disabled during the detection phase, allowing the target ions to move toward the second interdigital pole <NUM> for counting without further ionization of molecules. By disabling the ionization source <NUM> during the detection phase, the life of the ionization source <NUM> may be prolonged.

As the input gas <NUM> enters the PID detecting region <NUM> and interacts with the photons emitted from the ionization source <NUM>, a plurality of ionized molecules <NUM> are generated. Once molecules are ionized, the ionized molecules <NUM> carry an electric charge. As such, the molecules may become responsive to an electric field. In addition, ionized molecules may be de-ionized when they contact an electric source, such as an electrode. Further, ionized molecules may be detected when contacting an electric probe connected to a processing device.

As further depicted in <FIG>, the example PID VOC sensor <NUM> includes a separation voltage source <NUM> electrically connected to the first interdigital pole <NUM>. As described in relation to <FIG>, the applied separation voltage may be an asymmetric waveform comprising a repeating pattern, including a high voltage component lasting for a short period of time and a lower voltage component of opposing polarity lasting for a longer period of time. The separation voltage has the effect of separating ionized molecules based on the ratio of the molecule's mobility in a high electric field (Vh) to the molecule's mobility in a low electric field (Vl). Unequal mobilities will cause the ionized molecules to drift toward one interdigital pole or the other.

As further depicted in <FIG>, the example PID VOC sensor <NUM> includes a switch <NUM>. A switch <NUM> may be any mechanical, electromechanical, analog, or electrical device that allows an electrical connection between the second interdigital pole <NUM> and alternatively between the compensation voltage source <NUM> and the processing device <NUM>. The switch <NUM>, in some embodiments, may comprise a single pole double throw switch wherein the single input (e.g., single input connector) is electrically connected to the second interdigital pole <NUM> and one output (e.g., first output connector) is electrically connected to the compensation voltage source <NUM> while the other output (e.g., second output connector) is electrically connected to the processing device <NUM>. The switch <NUM> may be controlled through electrical communication by the processing device <NUM> or another similar device capable of electrical communication. In some embodiments, the switch <NUM> may be switched by receipt of a change in electrical signal (e.g., a change in voltage level) or by an electrical pulse. In some embodiments, the switch <NUM> state may be switched in coordination with the enabling/disabling of the ionization source <NUM>, as further described in relation to <FIG>.

As further depicted in <FIG>, the example PID VOC sensor <NUM> further includes a compensation voltage source <NUM> electrically connected to an output of the switch <NUM>. The switch <NUM> may be configured to connect the compensation voltage source <NUM> to the second interdigital pole <NUM> during the ionization and compensation phases. In an instance in which the switch <NUM> is configured such that an electrical connection is made between the compensation voltage source <NUM> and the second interdigital pole <NUM>, a compensation voltage may be provided to the second interdigital pole <NUM>. A compensation voltage may be any voltage applied to the second interdigital pole <NUM> to compensate for the drift of a target ion toward either interdigital pole (e.g., first interdigital pole <NUM> and second interdigital pole <NUM>). A compensation voltage may depend on a number of factors, including the mobility of the VOC ion of interest, the separation voltage, the pulse width of the compensation voltage waveform, the space between the electrodes, and other similar factors.

As one example, in general, a benzene VOC may require a lower compensation voltage, for example, between +<NUM> volts and +<NUM> volts. Thus, if a benzene ion when subjected to the separation voltage drifts toward the second interdigital pole <NUM>, the applied compensation voltage produced by the compensation voltage source <NUM> may force the benzene ion away from the second interdigital pole such that the net drift of the benzene ion is nullified and the target benzene ion remains in the electric field region <NUM> while the separation voltage oscillates the electric field in the electric field region <NUM>. Other targeted VOC ions may require a different compensation voltage. For example, an acetone ion may require a higher compensation voltage, for example, between +<NUM> and +<NUM> volts, to keep the targeted acetone ions in the electric field region <NUM>. In some embodiments, the compensation voltage source <NUM> may update or change the compensation voltage to detect other VOCs of interest during operation. In some embodiments, the compensation voltage source <NUM> may coordinate these updates with the enabling/disabling of the ionization source <NUM> and/or the switching of the switch <NUM>.

As further depicted in <FIG>, the example PID VOC sensor <NUM> further includes a processing device <NUM> electrically connected to an output of the switch <NUM>. The processing device <NUM> may be any device capable of detecting a change in voltage based on the presence of ions on the connected electrode (e.g., second interdigital pole <NUM>). In some embodiments, the processing device <NUM> may be a high speed signal processing circuit. The processing device <NUM> may be substantially connected during the detection phase of the VOC detection process. In addition to connecting the processing device <NUM> to the second interdigital pole <NUM>, the detection phase is defined by a constant voltage set on the first interdigital pole <NUM> (e.g., first constant DC voltage) and the second interdigital pole <NUM> (e.g., second constant DC voltage). In some embodiments, the constant voltage applied to the interdigital poles may be between <NUM> volts and <NUM> volts. Applying a constant voltage to the poles forces the ionized molecules to drift toward the second interdigital pole <NUM> for detection. The processing device <NUM> may determine a VOC value which, in some embodiments, may represent the presence of the targeted VOC. In some embodiments, the VOC value may represent the concentrations of a target VOC based on the change in voltage detected on the second interdigital pole <NUM>. In some embodiments, the detected signal will peak within a short time interval, for example <NUM> milliseconds to <NUM> milliseconds after the constant current on the interdigital poles has been applied.

In some embodiments, the processing device may configure the components of the PID VOC sensor <NUM>. For example, the processing device <NUM> may control the voltage output of the separation voltage source <NUM>, the enabling/disabling of the ionization source <NUM>, the switching of the switch <NUM>, the adjustment of the DC compensation voltage from the compensation voltage source <NUM>, and/or other similar configurable elements. In some embodiments, these configuration commands may be issued through wireless and/or wired communication between the components.

Referring now to <FIG>, a close-up view of the PID detecting region <NUM> is provided. The PID detecting region <NUM> may operate in three separate phases. First, the PID detecting region <NUM> operates in an ionization phase. During the ionization phase, the ionization source <NUM> is enabled. The ionization region <NUM> represents an area in which molecules present in the input gas <NUM> may interact with the ionization source and become ionized. The PID detecting region <NUM> may also operate in a separation phase. The separation phrase, in some embodiments, substantially overlaps with the ionization phase. The separation phase is characterized by the first interdigital pole <NUM> connected to a separation voltage source <NUM> and the second interdigital pole <NUM> connected via the switch <NUM> to the compensation voltage source <NUM>. During the separation phrase, non-targeted ions (e.g., ions <NUM>, <NUM>) drift toward one of the two interdigital poles based on the ratio of the mobility of the ion in the presence of a high electric field to the mobility of the ion in the presence of a low electric field (Kh/ Kl). However, the compensation voltage source <NUM> is configured to compensate the drift of targeted ions (e.g., ion <NUM>) during the separation phase, such that the targeted ions remain in the electric field region <NUM> during the separation phase. In general, the ionization source <NUM> is disabled sometime before the start of the detection phase. The detection phase is characterized by the switch <NUM>, electrically connecting the second interdigital pole to the processing device <NUM>, as well as the application of a constant DC voltage to the first interdigital pole <NUM> and the second interdigital pole <NUM>, forcing the targeted ions toward the second interdigital pole <NUM>. The processing device <NUM> may then determine a VOC value representing the presence and concentration of the targeted VOC based on the change in voltage on the second interdigital pole <NUM> due to contact with the now drifting targeted ions (e.g., ion <NUM>).

<FIG> illustrates an example processing device <NUM> in accordance with at least some example embodiments of the present disclosure. The processing device <NUM> includes processor <NUM>, input/output circuitry <NUM>, data storage media <NUM>, communications circuitry <NUM>, and ion detection circuitry <NUM>. In some embodiments, the processing device <NUM> is configured, using one or more of the sets of circuitry <NUM>, <NUM>, <NUM>, <NUM>, and/or <NUM>, to execute and perform the operations described herein.

Although components are described with respect to functional limitations, it should be understood that the particular implementations necessarily include the use of particular computing hardware. It should also be understood that in some embodiments certain of the components described herein include similar or common hardware. For example, two sets of circuitry may both leverage use of the same processor(s), network interface(s), storage medium(s), and/or the like, to perform their associated functions, such that duplicate hardware is not required for each set of circuitry. The user of the term "circuitry" as used herein with respect to components of the apparatuses described herein should therefore be understood to include particular hardware configured to perform the functions associated with the particular circuitry as described herein.

Particularly, the term "circuitry" should be understood broadly to include hardware and, in some embodiments, software for configuring the hardware. For example, in some embodiments, "circuitry" includes processing circuitry, storage media, network interfaces, input/output devices, and/or the like. Alternatively or additionally, in some embodiments, other elements of the processing device <NUM> provide or supplement the functionality of other particular sets of circuitry. For example, the processor <NUM> in some embodiments provides processing functionality to any of the sets of circuitry, the data storage media <NUM> provides storage functionality to any of the sets of circuitry, the communications circuitry <NUM> provides network interface functionality to any of the sets of circuitry, and/or the like.

In some embodiments, the processor <NUM> (and/or co-processor or any other processing circuitry assisting or otherwise associated with the processor) is/are in communication with the data storage media <NUM> via a bus for passing information among components of the processing device <NUM>. In some embodiments, for example, the data storage media <NUM> is non-transitory and may include, for example, one or more volatile and/or non-volatile memories. In other words, for example, the data storage media <NUM> in some embodiments includes or embodies an electronic storage device (e.g., a computer readable storage medium). In some embodiments, the data storage media <NUM> is configured to store information, data, content, applications, instructions, or the like, for enabling the processing device <NUM> to carry out various functions in accordance with example embodiments of the present disclosure.

The processor <NUM> may be embodied in a number of different ways. For example, in some example embodiments, the processor <NUM> includes one or more processing devices configured to perform independently. Additionally or alternatively, in some embodiments, the processor <NUM> includes one or more processor(s) configured in tandem via a bus to enable independent execution of instructions, pipelining, and/or multithreading. The use of the terms "processor" and "processing circuitry" should be understood to include a single core processor, a multi-core processor, multiple processors internal to the processing device <NUM>, and/or one or more remote or "cloud" processor(s) external to the processing device <NUM>.

In an example embodiment, the processor <NUM> is configured to execute instructions stored in the data storage media <NUM> or otherwise accessible to the processor. Alternatively or additionally, the processor <NUM> in some embodiments is configured to execute hard-coded functionality. As such, whether configured by hardware or software methods, or by a combination thereof, the processor <NUM> represents an entity (e.g., physically embodied in circuitry) capable of performing operations according to an embodiment of the present disclosure while configured accordingly. Alternatively or additionally, as another example in some example embodiments, when the processor <NUM> is embodied as an executor of software instructions, the instructions specifically configure the processor <NUM> to perform the algorithms embodied in the specific operations described herein when such instructions are executed.

As one particular example embodiment, the processor <NUM> is configured to perform various operations associated with the detection of VOCs in a gas. In some embodiments, the processor <NUM> includes hardware, software, firmware, and/or a combination thereof, that executes an ionization phase comprising exposing the gas to an ionization device (e.g., ionization source <NUM>) creating a plurality of ionized gas molecules. Additionally or alternatively, in some embodiments, the processor <NUM> includes hardware, software, firmware, and/or a combination thereof, that executes a separation phase comprising supplying a separation voltage to a first interdigital pole <NUM> disposed within the detecting region (e.g., PID detecting region <NUM>) and electrically connected to a separation voltage source <NUM> and supplying a compensation voltage to a second interdigital pole <NUM> disposed within the detecting region and electrically connected to a compensation voltage source <NUM> through a switch <NUM>. Additionally or alternatively, in some embodiments, the processor <NUM> includes hardware, software, firmware, and/or a combination thereof, that disables the ionization device upon completion of the ionization phase. Additionally or alternatively, in some embodiments, the processor <NUM> includes hardware, software, firmware, and/or a combination thereof, that executes a detection phase comprising: switching the switch <NUM> to electrically connect the second interdigital pole <NUM> to a processing device <NUM>; supplying a first direct current voltage to the first interdigital pole <NUM> and supplying a second direct current voltage to the second interdigital pole <NUM>; and determining a VOC value representative of a number of volatile organic compounds in the gas based at least in part on a number of ionized gas molecules that contact the second interdigital pole <NUM> while the second interdigital pole <NUM> is electrically connected to the processing device <NUM>.

In some embodiments, the processing device <NUM> includes input/output circuitry <NUM> that provides output to the user and, in some embodiments, to receive an indication of a user input. In some embodiments, the input/output circuitry <NUM> is in communication with the processor <NUM> to provide such functionality. The input/output circuitry <NUM> may comprise one or more user interface(s) (e.g., user interface) and in some embodiments includes a display that comprises the interface(s) rendered as a web user interface, an application user interface, a user device, a backend system, or the like. The processor <NUM> and/or input/output circuitry <NUM> comprising the processor may be configured to control one or more functions of one or more user interface elements through computer program instructions (e.g., software and/or firmware) stored on a memory accessible to the processor (e.g., data storage media <NUM>, and/or the like). In some embodiments, the input/output circuitry <NUM> includes or utilizes a user-facing application to provide input/output functionality to a client device and/or other display associated with a user.

In some embodiments, the processing device <NUM> includes communications circuitry <NUM>. The communications circuitry <NUM> includes any means such as a device or circuitry embodied in either hardware or a combination of hardware and software that is configured to receive and/or transmit data from/to a network and/or any other device, circuitry, or module in communication with the processing device <NUM>. In this regard, the communications circuitry <NUM> includes, for example in some embodiments, a network interface for enabling communications with a wired or wireless communications network. Additionally or alternatively in some embodiments, the communications circuitry <NUM> includes one or more network interface card(s), antenna(s), bus(es), switch(es), router(s), modem(s), and supporting hardware, firmware, and/or software, or any other device suitable for enabling communications via one or more communications network(s). Additionally or alternatively, the communications circuitry <NUM> includes circuitry for interacting with the antenna(s) and/or other hardware or software to cause transmission of signals via the antenna(s) or to handle receipt of signals received via the antenna(s). In some embodiments, the communications circuitry <NUM> enables transmission to and/or receipt of data from a client device in communication with the processing device <NUM>.

The ion detection circuitry <NUM> includes hardware, software, firmware, and/or a combination thereof, that supports various functionality associated with detecting volatile organic compounds (VOCs) in an input gas <NUM> diffused into a detecting region (e.g., PID detecting region <NUM>). For example, in some embodiments, the ion detection circuitry <NUM> includes hardware, software, firmware, and/or a combination thereof to execute an ionization phase comprising exposing the gas to an ionization source <NUM> creating a plurality of ionized gas molecules. Additionally or alternatively, in some embodiments, the ion detection circuitry <NUM> includes hardware, software, firmware, and/or a combination thereof, that executes a separation phase comprising supplying a separation voltage to a first interdigital pole <NUM> disposed within the detecting region and electrically connected to a separation voltage source <NUM>, and supplying a compensation voltage to a second interdigital pole <NUM> disposed within the detecting region and electrically connected to a compensation voltage source <NUM> through a switch <NUM>. Additionally or alternatively, in some embodiments, the ion detection circuitry <NUM> includes hardware, software, firmware, and/or a combination thereof, that disables the ionization source <NUM> upon completion of the ionization phase. Additionally, or alternatively the ion detection circuitry <NUM> includes hardware, software, firmware, and/or a combination thereof, that executes a detection phase comprising switching the switch <NUM> to electrically connect the second interdigital pole <NUM> to a processing device <NUM>, supplying a first direct current voltage to the first interdigital pole <NUM> and supplying a second direct current voltage to the second interdigital pole <NUM>, and determining a VOC value representative of the number of volatile organic compounds in the input gas <NUM> based at least in part on the number of ionized gas molecules that contact the second interdigital pole <NUM> while the second interdigital pole <NUM> is electrically connected to the processing device <NUM>. In some embodiments, the ion detection circuitry <NUM> includes a separate processor, specially configured field programmable gate array (FPGA), or a specially programmed application specific integrated circuit (ASIC).

Additionally or alternatively, in some embodiments, one or more of the sets of circuitry <NUM>-<NUM> are combinable. Additionally or alternatively, in some embodiments, one or more of the sets of circuitry perform some or all of the functionality described associated with another component. For example, in some embodiments, one or more sets of circuitry <NUM>-<NUM> are combined into a single module embodied in hardware, software, firmware, and/or a combination thereof. Similarly, in some embodiments, one or more of the sets of circuitry, for example ion detection circuitry <NUM>, is/are combined such that the processor <NUM> performs one or more of the operations described above with respect to each of these circuitry individually.

Referring now to <FIG>, an example PID VOC sensor housing <NUM> is provided. As shown in <FIG>, the example PID VOC sensor housing <NUM> includes a housing base <NUM> comprising a plurality of electrical connectors <NUM>. In some embodiments, the processing device <NUM> may be attached to the housing base <NUM>. In some embodiments, the processing device may be shaped to fit the cross-sectional shape of the PID VOC sensor housing <NUM> and/or the housing base <NUM> may comprise the processing device <NUM>. In some embodiments, the plurality of electrical connectors <NUM> (e.g., first electrical connector and second electrical connector) electrically connect to one or more pogo pin connectors <NUM>, extending beyond the side of the housing base <NUM> opposite the plurality of electrical connectors <NUM>, passing through the electrical connector opening <NUM> (as seen in <FIG>) in the interdigital pole bottom cover <NUM> (as seen in <FIG>), and contacting the first conducting pad <NUM> and the second conducting pad <NUM> of the interdigital pole component <NUM>.

The example PID VOC sensor housing <NUM>, as shown in <FIG>, further includes a housing wall <NUM>. The housing wall <NUM> extends from the base and forms an enclosed perimeter, defining an interior cavity <NUM>.

The example PID VOC sensor housing <NUM> further includes an ionization source contact coil <NUM> positioned between the ionization source <NUM> and an electrical conductor (not shown) on the housing base <NUM> int the interior cavity <NUM> of the PID VOC sensor housing <NUM>. The ionization source contact coil <NUM> provides electrical connectivity to the ionization source <NUM> and compressive force against the ionization source <NUM>, securing the ionization source <NUM> in a position against the interdigital pole component <NUM>. The position of the ionization source <NUM> enables the ionization source <NUM> to interact with the input gas <NUM> in the interdigital pole component <NUM> through the interdigital poles exposure window <NUM> (as seen in <FIG>).

As further illustrated in <FIG>, the interdigital pole component <NUM> is also disposed in the interior cavity <NUM> of the PID VOC sensor housing <NUM> against the ionization source <NUM> and secured into place by the housing cap <NUM>. In some embodiments, the housing cap <NUM> may be attached to the housing wall <NUM>, substantially sealing the interior cavity <NUM>. The housing cap <NUM> further comprises a cap vent <NUM> allowing input gas <NUM> to enter into the PID VOC sensor device and into the PID detecting region <NUM> (as seen in <FIG>) of the interdigital pole component <NUM>.

Referring now to <FIG>, an example PID VOC sensor signal sequence <NUM> is shown. Starting from the bottom, a compensation voltage switch output signal <NUM> is shown. As shown in <FIG>, when the compensation voltage switch output signal <NUM> is high, the PID VOC sensor <NUM> switch <NUM> switches the output to electrically connect the second interdigital pole <NUM> to the compensation voltage source <NUM>. While connected to the compensation voltage source <NUM>, the PID VOC sensor <NUM> is operating in the ionization and/or separation phase, in which non-targeted ionized ions drift toward one of the interdigital poles, while the targeted ions remain in the electric field region <NUM>. As further shown in <FIG>, when the compensation voltage switch output signal <NUM> is low, the PID VOC sensor <NUM> switch <NUM> switches the output to electrically connect the second interdigital pole <NUM> to the processing device <NUM>. While connected to the processing device <NUM>, the PID VOC sensor <NUM> is operating in the detection phase, in which a constant DC voltage is applied to both interdigital poles and the targeted ions drift to contact the second interdigital pole <NUM>. Once in contact with the second interdigital pole <NUM>, the processing device may determine a VOC value by converting the change in voltage to count and/or concentration of the targeted VOCs.

A compensation voltage source signal <NUM> is further illustrated in <FIG>. In some embodiments, a compensation voltage source <NUM> may apply a compensation voltage to the second interdigital pole <NUM> during the separation phase. The compensation voltage may be a DC voltage configured based on the mobility of the VOC ion of interest in the applied electric field. The compensation voltage may compensate for the drift of a target ion toward either interdigital pole (e.g., first interdigital pole <NUM> and second interdigital pole <NUM>). By applying a compensation voltage, the targeted ions will remain in the electric field region <NUM> during the separation phase, while other ionized molecules will drift toward one of the interdigital poles. As shown in the example compensation voltage source signal <NUM> of <FIG>, the compensation voltage may be adjusted between detection cycles. For example, a compensation voltage may be selected to target a first VOC. The selected compensation voltage is applied to the second interdigital pole <NUM> during the ionization and separation phases, separating the ionized molecules of the first VOC from other ionized molecules. The ionized molecules of the first VOC are then detected during the detection phase. The compensation voltage may then be adjusted to target a second VOC. The PID VOC sensor <NUM> will then cycle through the ionization, separation, and detection phases with the new compensation voltage, detecting the presence and concentration of the second VOC. This process can continue based on the number and type of VOCs detected.

A separation voltage signal <NUM> is further illustrated in <FIG>. As shown in <FIG>, during the separation phase of VOC detection, the applied separation voltage is an asymmetric waveform comprising a repeating pattern (e.g., <NUM>), including a high voltage component (e.g., <NUM>) lasting for a short period of time and a lower voltage component (e.g., <NUM>) of opposing polarity lasting for a longer period of time. The separation voltage has the effect of separating ionized molecules based on the molecule's mobility, causing the ionized molecules to drift toward one interdigital pole or the other. Adjustments may be made to the separation voltage and the compensation voltage to target a specific VOC based on the mobility of the ionized molecules of the VOC. As further illustrated in <FIG>, during the detection phase, a direct current voltage (e.g., <NUM>) is applied to the first interdigital pole <NUM>. Applying a constant voltage may cause the targeted ions remaining in the electric field region <NUM> to drift toward the second interdigital pole <NUM> for detection by the processing device <NUM>.

An ionization source input voltage signal <NUM> is further illustrated in <FIG>. The ionization source input voltage signal <NUM> illustrates an example voltage provided to the ionization source <NUM> during the operation of the PID VOC sensor <NUM>. As shown in <FIG>, when the ionization source input voltage signal <NUM> is high, the ionization source <NUM> is enabled. Alternatively, when the ionization source input voltage signal <NUM> is low, the ionization source is disabled. The ionization phase occurs while the ionization source <NUM> is enabled. During this phase, the ionization source <NUM> (e.g., UV lamp) interacts with the ions in the PID detecting region <NUM>. This interaction ionizes VOC molecules contained in the input gas <NUM>. In the example ionization source input voltage signal <NUM> shown in <FIG>, the ionization source <NUM> is turned off before the separation phase concludes. Shutting the ionization source <NUM> off before the conclusion of the separation phase allows the ionized molecules to finish drifting during the last cycle of the separation phase. Shutting the ionization source <NUM> off before the conclusion of the separation phase also ensures molecules are no longer being ionized during the detection phase. Enabling and disabling the ionization source <NUM> during the detection of VOCs, allows the ionization, separation, and detection phases to occur within the same physical space (e.g., PID detecting region <NUM>. Further, enabling and disabling the ionization source <NUM> may prolong the life of the ionization source <NUM>, particularly, in an instance in which the ionization source <NUM> is a UV lamp.

Referring now to <FIG>, an example method for detecting VOCs in a gas (e.g., input gas <NUM>) diffused into a detecting region (e.g., PID detecting region <NUM>) of a VOC sensor (e.g., PID VOC sensor <NUM>) is illustrated. The example method <NUM> starts at block <NUM> when a processing device (e.g., processing device <NUM>) executes an ionization phase comprising exposing the gas to an ionization source <NUM> creating a plurality of ionized gas molecules. During the ionization phase, the ionization source <NUM> is enabled. In some embodiments, the processing device may enable the ionization source <NUM>. The processing device may control the power output to the ionization source <NUM> through wired and/or wireless communication to a control device, for example, a switch. The processing device may signal a control device to enable power by sending a pulse or by changing an input voltage, for example, from a '<NUM>' to a '<NUM>. ' Further, a processing device may communicate with the control device through a synchronous protocol, such as I2C.

At block <NUM>, the processing device executes a separation phase comprising supplying a separation voltage to a first interdigital pole (e.g., first interdigital pole <NUM>) disposed within the detecting region (e.g., PID detecting region <NUM>) and electrically connected to a separation voltage source (e.g., separation voltage source <NUM>) and supplying a compensation voltage to a second interdigital pole (e.g., second interdigital pole <NUM>) disposed within the detecting region and electrically connected to a compensation voltage source (e.g., compensation voltage source <NUM>) through a switch (e.g., switch <NUM>). As previously described, the separation phase is characterized by a first set of interdigital poles connected to a separation voltage source delivering an asymmetric waveform comprising a repeating pattern (e.g., <NUM>), including a high voltage component (e.g., <NUM>) lasting for a short period of time and a lower voltage component (e.g., <NUM>) of opposing polarity lasting for a longer period of time, in an effort to separate targeted ions from other ionized compounds. The processing device may configure the output of the separation voltage source directly such that the voltage is provided as described above. In some embodiments, the separation voltage source may be attached to a switching mechanism such that the processing device enables the oscillating asymmetric waveform during the separation phase and enables a separate DC voltage source during the detection phase.

At block <NUM>, the processing device disables the ionization device (e.g., ionization source <NUM>) upon completion of the ionization phase. The processing device through communication mechanisms described with reference to block <NUM> may disable the ionization source previous to the conclusion of the separation phase, allowing the separation phase to conclude and ensuring molecules are no longer being ionized during the detection phase.

At block <NUM>, the processing device executes a detection phase comprising switching the switch to electrically connect the second interdigital pole <NUM> to the processing device, supplying a first direct current voltage to the first interdigital pole <NUM> and supplying a second direct current voltage to the second interdigital pole <NUM>, and determining a VOC value representative of a number of volatile organic compounds in the gas based at least in part on a number of ionized gas molecules that contact the second interdigital pole <NUM> while the second interdigital pole <NUM> is electrically connected to the processing device. The detection phase is characterized by applying a DC voltage to both the interdigital poles and electrically connecting the processing device to at least one of the interdigital poles. The processing device may configure the switch (e.g., switch <NUM>) to electrically connect at least one of the interdigital poles to the processing device. The processing device may further provide a constant DC voltage to the set of interdigital poles connected to the separation voltage source. In some embodiments, the processing device may directly configure the separation voltage source to output a constant DC voltage. In some embodiments, the processing device may configure a switch to switch between the separation voltage source and a constant DC voltage source once the separation phase has completed. Similarly, the processing device may enable a constant DC voltage on the interdigital poles connected to the processing device through a switching mechanism, or by providing the DC voltage source directly.

The processing device may further determine a VOC value based on the number of detected VOCs. In some embodiments, the VOC value may represent the presence of VOCs. For example, if the increase in voltage due to the presence of detected ions is greater than a threshold, the VOC value indicates that the VOC is present in the gas, otherwise, the VOC value indicates that no VOCs are present. In some embodiments, the VOC value may represent the total number of VOCs detected in the given time range based on the detected increase in voltage due to the detected ionized VOCs. In some embodiments, the VOC value may represent the number of detected VOCs over a range of compensate voltages. For example, the PID VOC sensor <NUM> may cycle through a range of compensate voltages, recording the increase in voltage due to the detected ions at each incremental compensate voltage. A VOC value may be a curve and/or graph representing the change in VOCs based on the compensate voltage.

Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of teachings presented in the foregoing descriptions and the associated drawings. Although the figures only show certain components of the apparatus and systems described herein, it is understood that various other components may be used in conjunction with the system. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, the steps in the method described above may not necessarily occur in the order depicted in the accompanying diagrams, and in some cases one or more of the steps depicted may occur substantially simultaneously, or additional steps may be involved. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claim 1:
An apparatus for detecting volatile organic compounds, VOCs, in a gas, the apparatus comprising:
a processing device (<NUM>);
a compensation voltage source (<NUM>);
a separation voltage source (<NUM>); and
a detecting region (<NUM>) comprising:
a first interdigital pole (<NUM>) disposed within the detecting region and electrically connected to the separation voltage source (<NUM>);
a second interdigital pole (<NUM>) disposed within the detecting region and electrically connected to a switch (<NUM>); and
an ionization device configured to interact with a gas within the detecting region creating a plurality of ionized gas molecules;
wherein the switch (<NUM>) is configured to alternate the connection of the second interdigital pole (<NUM>) between the compensation voltage source (<NUM>) and the processing device (<NUM>); and
wherein the processing device (<NUM>) is configured to determine a VOC value representative of a number of volatile organic compounds in the gas based at least in part on a number of ionized gas molecules that contact the second interdigital pole (<NUM>) while the second interdigital pole (<NUM>) is electrically connected to the processing device (<NUM>).