Patent Description:
Identification and detection of materials may be beneficial in a variety of settings. The disclosure provides for a vapor and particulate sensor system that may be utilized to detect airborne chemical compositions for various applications. The disclosure of <CIT> provides for a detector including a plurality of nanofiber chemical sensors, each having an electrical characteristic. A processing and alarm circuit is in electrical communication with the plurality of nanofiber chemical sensors. The electrical characteristics of the plurality of nanofiber chemical sensors change in the presence of a first airborne material. The electrical characteristics of at least one of the plurality of nanofiber chemical sensors changes in the presence of a second airborne material. The changes in the electrical characteristics of the at least one of the plurality of nanofiber chemical sensors in the presence of the first airborne material are different from the changes in the electrical characteristics of at least one of the plurality of nanofiber chemical sensors in the presence of the second airborne material. The disclosure of <CIT> provides for a smoke detector of an obscuration-type that has an effective light propagation path of substantially greater length than the light propagation paths of conventional obscuration-type smoke detectors to provide increased smoke detection sensitivity without increased background noise or numbers of false alarm incidents. The smoke detector has a light source that emits a light beam that propagates into a detection chamber composed of first and second optical components having respective first and second opposed light reflecting surfaces. The light reflecting surfaces reflect the light beam across the detection chamber multiple times before the reflected light beam is incident on a light detector. The multiple reflections of the light beam increase its effective path length of propagation within the detection chamber to provide the increased smoke detection sensitivity. The disclosure of <CIT> provides for a gas analysis system and method of identifying analytes in a gas sample. The system uses multiple gas analysis technologies and uses the combined qualitative and quantitative data obtained from the multiple gas analysis technologies to analyze a gas sample.

According to one aspect of the present disclosure, a detection system is disclosed. The system comprises at least one sensor configured to measure a presence of airborne particles and at least one amplifier circuit in communication with the at least one sensor. The amplifier circuit is configured to monitor a charge generated by the at least one sensor over a time interval. The system further comprises a controller configured to monitor the charge accumulated in the at least one amplifier circuit from the at least one sensor at the time interval. In response to the charge of the at least one amplifier circuit, the controller detects the presence of the airborne particles.

According to another aspect of the disclosure, a method for detecting a presence of airborne particles is disclosed. The method comprises supplying a plurality of bias voltages to a plurality of chemical sensors. The method further comprises receiving and accumulating current from each of the chemical sensors with a corresponding amplifier circuit and monitoring charges accumulated in the amplifier circuits from each of the chemical sensors over a plurality of corresponding accumulation periods. The method further comprises determining the resistance of each of the chemical sensors based on the charge of the amplifier circuits and voltage values of the plurality of bias voltages. The presence of the airborne particles is determined based on the resistances or conductance values determined for the chemical sensors.

According to yet another aspect of the disclosure, a chemical detection system comprising a plurality of chemical sensors configured to vary in resistance in response to a presence of airborne particles and a bias circuit configured to supply bias voltages to each of the chemical sensors. The system further comprises a plurality of amplifier circuits in communication with the chemical sensors and a controller. The controller is configured to control the bias circuit to supply the plurality of bias voltages to each of the plurality of chemical sensors and monitor charges accumulated in the amplifier circuits from the chemical sensors over the corresponding integration period in response to the bias voltages. The controller is further configured to determine the resistance of the chemical sensors based on the charges accumulated in the amplifier circuits and voltage values of the plurality of bias voltages and detect a chemical composition of the airborne particles based on the determined resistances of the chemical sensors.

These and other aspects, objects, and features of the present disclosure will be understood and appreciated by those skilled in the art upon studying the following specification, claims, and appended drawings. It will also be understood that features of each example disclosed herein may be used in conjunction with, or as a replacement for, features of the other examples.

The following is a description of the figures and the accompanying drawings. The figures are not necessarily to scale, and certain features and certain views of the figures may be shown exaggerated in scale or in schematic in the interest of clarity.

It is to be understood that the specific devices and processes illustrated in the attached drawings and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. As used herein, the term "and/or," when used in a list of two or more items, means that any of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed.

In this document, relational terms, such as first and second, top and bottom, and the like, are used solely to distinguish one entity or action from another entity or action, without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises. a" does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

Referring now to <FIG>, the disclosure provides for a detection system <NUM> configured to detect a variety of airborne chemical compounds or other measurable conditions. In various implementations, the system <NUM> may comprise a controller <NUM> configured to monitor and control a chemical detection device <NUM>. The chemical detection device <NUM> is designed to identify a type and/or concentration of various chemicals based on signals communicated from at least one sensor <NUM> or a plurality of sensors <NUM> in an array <NUM>. In various implementations, the at least one sensor <NUM> may be incorporated in a modular housing <NUM> forming the detection device <NUM>. Accordingly, the disclosure provides for a chemical detection system <NUM> that may be flexibly applied in a variety of environments to detect one or more chemicals as provided by the following description.

Depending on the application of the system <NUM>, each of the sensors 14a, 14b, 14c, etc. may be configured to detect specific chemicals or compounds that may be present in the environment local to the array <NUM>. Similarly, signals from two or more of the sensors <NUM> in combination may be interpreted by the system <NUM> to identify the presence of a chemical or combination of chemicals. Such a detection may be inferred by the controller <NUM> based on an identifying signature or a combination of signals from the sensors <NUM> that are detected in response to and are representative of the presence of one or more chemicals or compounds. In this way, the system <NUM> may be scaled or tailored to suit a desired application based on the characteristics of each of the sensors <NUM>. Accordingly, the system <NUM> may be configured to detect the presence of a variety of chemicals proximate to the array <NUM>.

The signals output from the sensors <NUM> may comprise subtle changes in current. Such small changes, when considered in combination with signal noise and fluctuations that may occur over time, may result in the signals having transient variations that may cause issues identifying the status of the sensors <NUM>. Accordingly, to accurately identify the presence of the chemicals, the system <NUM> may comprise a monitor circuit <NUM> configured to detect and communicate information that may be analyzed by the controller <NUM> to determine the resistance of each of the sensors 14a, 14b, 14c, etc. and to infer the chemicals present based on the resistance.

To effectively measure changes in the chemical composition of the environment proximate to the array <NUM>, the monitor circuit <NUM> may be highly sensitive while also being capable of filtering noise related to transient variations output from each of the sensors 14a, 14b, 14c, etc. Accordingly, the monitor circuit <NUM> may comprise an amplifier circuit <NUM> configured to filter and track the changes in the current output from each of the sensors 14a, 14b, 14c, etc. over an integration period. The integration period may correspond to a monitoring interval over which the current output from each of the sensors 14a, 14b, 14c, etc. is accumulated. In response to a duration of the integration period for each of the sensors 14a, 14b, 14c, etc. expiring, the controller <NUM> may be configured to activate a readout circuit <NUM> (e.g. an analog-to-digital converter [ADC]) to read or convert the charges accumulated on the amplifier circuit <NUM> to digital values. Such values may then be reported by the controller <NUM> and/or stored, such that variations in the resistance of each of the sensors 14a, 14b, 14b, etc. of the array <NUM> may be calculated. Further detailed discussion of the sensor array <NUM> and the monitor circuit is provided in reference to <FIG>.

In some implementations as exemplified in <FIG>, the readout circuit <NUM> may be implemented with a zero-crossing detector 24a and a capture timer 24b. The "zero" point may have a magnitude greater than zero in a unipolar power supply implementation. As shown, the integration block is modified, such that the controller <NUM> can select either the unknown current or a reference current of opposite polarity to the unknown. In operation, the unknown is integrated for a known time period. The reference is then integrated until the output of the integrator reaches the zero level. The capture timer 24b measures this re-zero time. This re-zero time is directly proportional to the unknown current. This measurement method may be referred to as dual-slope A/D conversion and is capable of very high resolution. The capture timer 24b may be implemented in a microprocessor peripheral or other digital hardware. Dual-slope A/D conversion is less complex and low cost than many other A/D conversion methods, but also tends to have a slow conversion rate. For some applications, this combination of high, resolution, low-cost, and slow conversion may be beneficial.

In addition to the sensitive nature of the signals output from the sensors <NUM>, the operation of each of the sensors 14a, 14b, 14b, etc. may be dependent on the input signal supplied to the sensors <NUM>. Accordingly, the system <NUM> may further comprise a sensor bias circuit <NUM>. The sensor bias circuit <NUM> may comprise one or more circuits configured to supply a voltage to each of the sensors 14a, 14b, 14c, etc. in response to a control signal from the controller <NUM>. For example, the sensor bias circuit <NUM> may comprise a plurality of converters (e.g., digital-to-analog converters [DAC]) configured to generate input signals supplied to each of the sensors 14a, 14b, 14c, etc. In this configuration, the controller <NUM> may be configured to supply independent control signals to each of the sensors 14a, 14b, 14c, etc. The independent control signals may differ in timing, voltage, frequency, and other characteristics that may support the operation of each of the sensors 14a, 14b, 14b, etc. of the array <NUM> to accurately respond to the presence of chemicals proximate to the array <NUM>.

Though discussed in reference to specific sensors (e.g. nanofiber chemical sensors), the chemical detection device <NUM> may comprise a variety of sensory devices. For example, the chemical detection device <NUM> may be implemented by a variety of devices including, but not limited to, electrochemical sensors, amperometric gas sensors, carbon monoxide sensors, catalytic bead sensors, thermal conductivity sensors, metal oxide sensors (MOS), infrared (IR) sensors, photoionization detectors (PID), etc. Such sensors may vary in application and, therefore, may be implemented in various combinations to achieve the identification and detection of various chemicals and contaminants that may be present proximate to the detection device <NUM>.

As discussed herein, the controller <NUM> may comprise one or more processors or microcontrollers, a field-programmable gate array (FPGA), application-specific integrated circuit (ASIC), or other processing devices depending on the application. For example, if the sensors <NUM> of the device <NUM> are not very numerous, a simple processing unit may be sufficient to enable basic detection via the associated sensors <NUM>. However, if the sensors <NUM> are more numerous and the corresponding control structure requires more concurrent or programmable operations, the FPGA may be better suited to provide for the operation of the controller <NUM> as discussed herein. As discussed in reference to <FIG> and <FIG>, the detection device <NUM> may be configured for more than one sensor, which may suggest the necessity for a complicated control structure. As discussed herein, such a control structure may include an independent supply of bias voltage via the sensor bias circuit <NUM> as well as independent readout timing control and readout of the charges associated with each of the sensors 14a, <NUM>, 14c, etc. In some implementations, the sensor bias circuit <NUM> may also include bias resistors, such that a negative or positive signal may be supplied to each of the sensors <NUM>.

In some embodiments, the controller <NUM> may further be in communication with one or more communication circuits <NUM> configured to communicate with one or more external devices, computers, and/or user interfaces. In some embodiments, the communication circuit <NUM> may correspond to a wired connection (e.g., Universal Serial Bus (USB), Thunderbolt, External Serial Advanced Technology Attachment (eSATA), etc. Additionally, the controller may comprise a wireless network interface. As discussed herein, wireless communication protocols may operate in accordance with communication standards including, but not limited to, ground air cellular towers, global system for mobile communications (GSM), code division multiple access (CDMA), Long Term Evolution (LTE or <NUM> LTE), etc.; satellite-based communications; and/or variations thereof. Accordingly, the controller <NUM> of the system <NUM> may be configured to send alerts or signals to various devices configured to communicate via one or more wired or wireless communication protocols.

Referring now to <FIG> and <FIG>, an example of the detection device <NUM> is shown in communication with at least one of the nanofiber chemical sensors <NUM>. The nanofiber chemical sensor <NUM> may be configured to sense various chemicals and compounds that may be present in the ambient air proximate to the housing <NUM>. In some embodiments, the at least one nanofiber chemical sensor <NUM> may comprise a plurality of nanofiber chemical sensors 14a-14p. Though identified in this particular example to include sixteen sensors <NUM>, the number of sensors <NUM> may vary and be adjusted to suit a desired application. In operation, each of the one or more nanofiber chemical sensors <NUM> may be in communication with the controller <NUM>, which may be configured to monitor changes in electrical characteristics for each of the nanofiber sensors <NUM> in the presence of the various airborne materials. Based on the combination of signals received from chemical sensors <NUM>, the controller <NUM> may be configured to identify the presence of one or more contaminants proximate to the detection device <NUM>.

The nanofibers used in the sensors <NUM> may be synthesized with specific functional groups that can interact with airborne materials/vapors/particles. The nanofibers are deposited on an interdigitated electrode to form an electrode-nanofiber array. Interaction of the nanofibers with airborne materials changes the measured electrical characteristics of the nanofiber chemical sensor. An increase or decrease in the measured current or effective resistance of each of the nanofiber chemical sensors occurs as a result of these airborne material interactions.

Nanofibers of each of the sensors <NUM> with different functional groups have a different response to the same airborne material. By using the plurality of nanofiber chemical sensors <NUM> in the array <NUM>, an identifying response signature can be established by the controller <NUM> for each of a plurality of airborne materials. Accordingly, based on the electrical signals communicated from the array <NUM>, the controller <NUM> may be configured to detect a variety of conditions that may exist proximate to the sensor array <NUM>. The nanofibers of the sensors <NUM> may have a proportionately large three-dimensional surface area that is resistant to particulate fouling. In various embodiments, the controller <NUM> may be configured to identify a variety of contaminants. In response to the particular contaminant or family of contaminants identified by the detection device <NUM>, the system <NUM> may be configured to respond by outputting information that may assist in the detection or correction of a condition related to the detection.

In various embodiments, the detection device <NUM> may be configured to identify a variety of chemicals present in a detection zone or region. Chemicals and compounds that may be detected by the system <NUM> may be trained or programmed based on electrical signatures received by the controller <NUM> in response to the presence of the chemicals. Examples of chemicals that may be identified and/or detected may include, but are not limited to, Benzaldehyde, Hexane, Acetone, Ethanol, Diesel Fuel, Nitrobenzene, and Formaldehyde. Some examples of explosives and chemical agents that may be detected may include Nitromethane, DNT (Dinitrotoluene), TNT (Trinitrotoluene), ANFO (Ammonium Nitrate Fuel Oil), Ammonium Nitrate, PETN (may detect taggant), RDX (may detect taggant), TATP (Triacetone Triperoxide), H2O2 (Hydrogen Peroxide), TEP (Triethylphosphate), DMMP (Dimethyl methylphosphonate), <NUM>-Chloroethyl ethyl sulfide, Triphosgene, and Methyl Salicylate. Some examples of toxic chemicals that may be detected by the detection device <NUM> include, but are not limited to, Chlorine Gas, Ammonia, Hydrogen Peroxide, Sulfur Dioxide, Hydrochloric Acid, TEP (Triethyl Phosphate), Phosphine, Hydrogen Cyanide, Arsine, and Formaldehyde. In some examples, the detection device may also be configured to detect one or more chemicals commonly found in consumer foods and/or goods including, but not limited to, Trichloroanisole, Melamine, Trimethylamine, Limonene, Pinene, Linalyl acetate, Menthol, Menthone, and Linalool. The device <NUM> may additionally be configured to detect various amines including, but not limited to, N-Methylphenethylam-lamine, Phenethylamine, Methylamine, Aniline, Triethylamine, and Diethylamine. Accordingly, based on the detection of each of the chemicals detected by the controller <NUM>, a signal or information may be communicated via the communication circuit <NUM> to indicate the chemical presence.

Referring now to <FIG>, the chemical sensors 14a-14p of the detection device <NUM> may be arranged in any manner and may be disposed in an inner chamber <NUM> of the housing <NUM> having a plurality of air vents <NUM>. The air vents <NUM> may provide for ambient and/or forced air to flow into the inner chamber <NUM>. In this configuration, updated air samples flow past the chemical sensors 14a-14p providing consistently updated monitoring of the chemical particulates present in the air. In various implementations, the air vents <NUM> may be large enough and/or numerous enough to allow the ambient air to flow into the inner chamber <NUM> without restriction. The controller <NUM> may be in communication with various systems and/or controllers that may be associated with additional devices and/or interfaces via the communication circuit <NUM>. In various implementations, the communication circuit <NUM> may correspond to a wired and/or wireless connection. Accordingly, the system <NUM> may be configured to communicate one or more warnings, instructions, and/or additional information to a user, device, or remote server in response to the detection of one or more chemicals via the detection device <NUM>.

Common chemicals and corresponding odors that may be detected by the device <NUM> may vary widely. For example, the device <NUM> may be configured to identify a variety of odors including, but not limited to, perfumes, feces, fish, skunk, pet odor, decaying biological material, methane, hydrogen sulfide, body odor (body-related bacterial odor), smoke, alcohol, bodily fluids, vomit, etc. Some of these odors may relate to comfort issues while others could present health issues or security concerns to those exposed. Accordingly, the system <NUM> may additionally communicate a concentration of the chemicals detected by the device <NUM> via the communication circuit <NUM> of the controller <NUM>.

Additionally, the detection device <NUM> may be configured to detect and identify a variety of chemicals that may generally be considered dangerous, which may or may not cause a significant odor. Examples of such chemicals or sources of such chemicals may be allergens including, but not limited to, peanuts, soy, perfumes, smog, etc. Additional examples of chemicals or sources of such chemicals may include, but are not limited to, explosives, gun powder, accelerants, carbon dioxide, carbon monoxide, volatile organic compounds (VOCs), drugs (e.g. methamphetamine, alcohol), smog, smoke, exhaust, etc. In response to the detection of such chemicals, the system <NUM> may respond in different ways, particularly in comparison to the detection of chemicals that may not be dangerous to users or individuals in the area of the detection device <NUM>.

Referring now to <FIG>, a diagram of the sensor array <NUM> is shown in conductive communication with the sensor bias circuit <NUM>. As previously described, the sensor bias circuit <NUM> may be configured to supply an analog voltage to each of the sensors 14a, 14b, 14c, etc. in response to a control signal from the controller <NUM>. For example, the sensor bias circuit <NUM> may comprise a plurality of digital-to-analog converters (DACs) configured to generate voltages ranging from approximately ±15V in response to digital input signals supplied by the controller <NUM>. In this configuration, the controller <NUM> may be configured to supply independent control signals to control the bias voltage delivered to each of the sensors 14a, 14b, 14c, etc. Additionally, the controller10 may supply each of the sensors 14a, 14b, 14c, etc. with the bias voltage or control signal at different times and frequencies depending on the desired operation of each of the sensors 14a, 14b, 14c, etc. for an application and other characteristics that may support the operation of each of the sensors 14a, 14b, 14b, etc. of the array <NUM> to accurately detect the chemicals proximate to the array <NUM>.

As depicted, the sensors <NUM> of the sensor array <NUM> may correspond to chemiresistors, which are shown modeled as variable resistors. The sensors <NUM> may be formed of nanofibers disposed between interdigitated fingers of electrode pairs. The nanofibers may form a porous structure across the electrode pairs configured to capture targeted molecules in the air proximate to the detection device <NUM>. When the nanofibers come in contact with target analytes or chemicals, a change in the electrochemical characteristics of the nanofibers may occur. The change in electrochemical characteristics may result in increases or decreases in the signal output to the amplifier circuit <NUM>. An input side of the electrode pair may be connected to the sensor bias circuit <NUM>, and an output side of the electrode pair may be connected to the amplifier circuit <NUM> (e.g., 22a, 22b, etc.). As shown, the amplifier circuits <NUM> connected to the sensors <NUM> may form an amplifier array <NUM>.

In operation, the controller <NUM> may be configured to control an exposure of each of the sensors 14a, 14b, etc. to a light source (not shown). The light source may induce photocurrent across the nanostructure, which may reduce the resistance of the nanofiber structure between the electrode pair as well as increase the reactive nature of the nanofibers to chemicals coming in contact with the nanofibers. In this configuration, the current passing through each of the sensors 14a, 14b, etc. may vary independently in response to the exposure of different chemical structures that contact or are captured in the porous structures of the different sensors <NUM> of the sensor array <NUM>. The small changes in current may be accumulated over exposure times by a capacitor <NUM> of each of the amplifier circuits 22a, 22b, etc. Once the exposure time has elapsed, the controller <NUM> may control a first switch 56a. The first switch 56a may be configured to cause the accumulated charge to be held in the capacitor <NUM>, such that the corresponding charge may be read out by the readout circuit <NUM> (e.g. an analog-to-digital converter [ADC]) and communicated to the controller <NUM> from an op-amp <NUM> of the amplifier circuit <NUM>.

Once the charge is read out from the amplifier circuit <NUM>, the controller <NUM> may be configured to control a second switch 56b to reset or discharge the capacitor <NUM>, such that the accumulation of the current may again be measured over an integration period. In this way, the accumulated charges of each of the sensors <NUM> of the array <NUM> may be monitored and processed by the controller <NUM> and/or additional computers or controllers to determine variations in resistance in the resistance of the sensors <NUM>. Based on the variations in the resistances of the sensors <NUM> and the corresponding changes in the charges accumulated in the capacitors, the controller <NUM> may determine or infer the chemical compositions or types of materials to which the detection device <NUM> is exposed. As discussed herein, the controller <NUM> may be configured to independently adjust the duration and timing (e.g. frequency) of the integration period of each of the sensors <NUM>. Additionally, the controller <NUM> may adjust the integration periods of the amplifier circuits <NUM> over time in order to ensure that the accumulated charges are sufficient to measure and limited to avoid saturation of the capacity of the capacitor <NUM>. In this way, the controller <NUM> may monitor and compute the changes in the resistance of each of the sensors <NUM>.

As depicted in <FIG>, the amplifier circuits <NUM> each comprise the op-amp <NUM> conductively connected to the bias output at an inverting input. The first switch 56a (e.g. a hold switch) may be disposed between the bias output and the inverting input allowing the controller <NUM> to selectively disconnect the bias output from the amplifier circuit <NUM>. The non-inverting input of the op-amp <NUM> may be connected to the ground, and the output may be in connection with the readout circuit <NUM>. The second switch 56b (e.g. a reset switch) and the capacitor <NUM> may be connected in parallel from the inverting input to the output of the op-amp <NUM>. In this configuration, each of the amplifier circuits 22a, 22b, etc. may be configured to integrate a charge supplied by each of the sensors 14a, 14b, etc. and supply a charge value to the readout circuit <NUM>. The charge value is representative of a resistance of each of the sensors 14a, 14b, etc. and may be calculated based on the known voltage supplied to the sensors <NUM> over the integration period or a time interval, which is also controlled by and known by the controller <NUM>. In this way, the resistance of each of the sensors 14a, 14b, etc. at a sample time may be identified by the controller <NUM> to infer or calculate a concentration of a chemical compound proximate to the detection device <NUM> while filtering transient spikes and noise that may otherwise cause significant error.

The chemical composition of the airborne material detected by the sensors 14a, 14b, etc. may be distinguished from a plurality of chemical compositions based on a combination of the resistances identified for the sensors 14a, 14b, etc. Such combinations of resistances may correspond to representative resistance characteristics or resistance signatures that are compared by the controller <NUM> to a table or library of resistance characteristics for various chemical compositions. In this way, the controller may compare the detected resistances to the resistance characteristics to identify the specific chemical composition and distinguish the composition from various chemical compositions that may be identified by the system <NUM>. In other words, the system <NUM> may monitor and compare the resistances of the sensors 14a, 14b, etc. and compare the resistances to corresponding combinations of resistance values of the sensors 14a, 14b, etc. that correlate to the presence of specific chemical compositions or families of chemicals. Accordingly, by monitoring the resistances of the sensors 14a, 14b, etc., the system <NUM> may determine or detect the presence of various chemical compositions based on the resistances of the sensors 14a, 14b, etc. as indicated by the characteristic response of the sensors 14a, 14b, etc. to the chemical composition.

Referring now to <FIG>, the readout circuit <NUM> may be implemented with a zero-crossing detector 24a (e.g. comparator) and a capture timer 24b. As shown, the integration block is modified such that the controller <NUM> can select either the unknown current or a reference current of opposite polarity to the unknown via a three-way switch, which may be referred to as an integration switch 56c. The integration switch 56c is in connection with the inverting input of the op-amp <NUM>. In operation, the unknown current is integrated for a known time period. The reference is then integrated until the output of the integrator reaches the zero level. The capture timer 24b measures this re-zero time. This re-zero time is directly proportional to the unknown current.

Referring now to <FIG>, a circuit diagram of an amplifier circuit <NUM> as discussed herein is shown. The amplifier circuit <NUM> may be similar to the amplifier circuit <NUM> and accordingly, the description of the amplifier circuit <NUM> may focus on the aspects that may differ, and like reference numerals may be used to refer to like parts. The amplifier circuit <NUM> may comprise the op-amp <NUM> conductively connecting the bias output to an inverting input of the op-amp <NUM>. The non-inverting input of the op-amp <NUM> may be connected to a ground. The second switch 56b (e.g. a reset switch) and the capacitor <NUM> may be connected in parallel from the inverting input to the output of the op-amp <NUM>. The first switch 56a may be connected in series between the output of the op-amp <NUM> and the parallel connection of the capacitor <NUM> with the second switch 56b.

Additionally, a third switch 56c may be configured to selectively connect the capacitor <NUM> to a reference voltage Vref. The third switch 56c may also be controlled by the controller <NUM> and may be connected in series between an input of the reference voltage Vref and the parallel connection of the capacitor <NUM> with the second switch 56b. Finally, the amplifier circuit <NUM> may further comprise a charging switch 56d connected from the inverting input of the op-amp <NUM> to the ground. The operation of the charging switch 56d may also be controlled by the controller <NUM> and provide for the control of the charging of the capacitor <NUM>. Accordingly, the disclosure may implement the amplifier circuit <NUM> to monitor a charge generated by the at least one sensor over a time interval as provided by the disclosure.

Referring now to <FIG>, a schematic diagram of a light detection system <NUM> is shown demonstrating a photosensor <NUM> (e.g. a photodiode) configured to monitor a light transmitted from an emitter <NUM> (e.g. a light-emitting diode [LED], halogen bulb, xenon bulb, etc.). Though discussed in reference to the emitter <NUM>, the photosensor <NUM> may similarly be applied to monitor an environmental light source or daylight condition. In operation, a controller <NUM> may be configured to activate the emitter <NUM> and monitor the light received by the photosensor <NUM>. Similar to the sensors <NUM> of the detection device <NUM>, the photosensor <NUM> may vary in output current in response to a local environment. The photosensor <NUM> may react by varying in photocurrent output to the amplifier circuit <NUM>, <NUM> based on changes in light impinging upon the photosensor <NUM>. In this way, the controller <NUM> may detect fluctuations in the light received by the photosensor <NUM> from the emitter <NUM>. In some implementations, the controller <NUM> may infer or determine the presence of a particle in an open region <NUM> between the emitter <NUM> and the photosensor <NUM> and make inferences as to the quality, condition, and/or transmittance or transparency of air in the open region <NUM>. Similarly, the controller <NUM> may be configured to determine a brightness or relative luminance of a local environment in instances where the emitter <NUM> is not controlled by the controller <NUM> and instead corresponds to an environmental light source or external light source (e.g. the sun, streetlights, etc.). Accordingly, the disclosure provides for a flexible solution that may be implemented in a variety of beneficial implementations.

As discussed herein the light detection system may correspond to a smoke or particulate sensor as discussed in <CIT>, entitled "COMPACT PARTICLE SENSOR," <CIT>, entitled "SMOKE DETECTOR," <CIT>, entitled "SMOKE DETECTOR," and <CIT>, entitled "SMOKE DETECTOR,".

It will be understood by one having ordinary skill in the art that construction of the described device and other components may not be limited to any specific material. Other exemplary embodiments of the device disclosed herein may be formed from a wide variety of materials unless described otherwise herein.

Such joining may be permanent or may be removable or releasable unless otherwise stated.

It is also important to note that the construction and arrangement of the elements of the device as shown in the exemplary embodiments is illustrative only. Although only a few embodiments of the present innovations have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes, and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited. For example, elements shown as integrally formed may be constructed of multiple parts or elements shown as multiple parts may be integrally formed, the operation of the interfaces may be reversed or otherwise varied, the length or width of the structures and/or members or connector or other elements of the system may be varied, the nature or number of adjustment positions provided between the elements may be varied. It should be noted that the elements and/or assemblies of the system may be constructed from any of a wide variety of materials that provide sufficient strength or durability, in any of a wide variety of colors, textures, and combinations. Accordingly, all such modifications are intended to be included within the scope of the present innovations.

It will be understood that any described processes or steps within described processes may be combined with other disclosed processes or steps to form structures within the scope of the present device. The exemplary structures and processes disclosed herein are for illustrative purposes and are not to be construed as limiting.

It is also to be understood that variations and modifications can be made on the aforementioned structure without departing from the concepts of the present invention, and further it is to be understood that such concepts are intended to be covered by the following claims unless these claims by their language expressly state otherwise.

Claim 1:
A detection system (<NUM>) comprising:
at least one sensor (<NUM>) configured to measure a presence of airborne particles,
wherein the at least one sensor (<NUM>) comprises a nanofiber chemical sensor (<NUM>) for sensing a chemical composition of the airborne particles, and
wherein the nanofiber chemical sensor (<NUM>) comprises a variable resistance that varies in response to a concentration of the chemical composition of the airborne particles;
at least one amplifier circuit (<NUM>) in communication with the at least one sensor (<NUM>),
wherein the amplifier circuit (<NUM>) is configured to monitor a charge generated by the at least one sensor (<NUM>) over a time interval; and
a controller (<NUM>) configured to:
monitor the charge accumulated in the at least one amplifier circuit (<NUM>) from the at least one sensor (<NUM>) at the time interval; and
in response to the charge of the at least one amplifier circuit (<NUM>), detect the presence of the airborne particles,
wherein the controller (<NUM>) is further configured to:
detect the concentration of the chemical composition in response to identifying changes in the variable resistance, wherein the changes in the variable resistance are determined based on the charge of the at least one amplifier circuit (<NUM>) and a voltage potential of a bias voltage supplied to the at least one nanofiber chemical sensor (<NUM>).