JP2015210188A - Particle measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a particle measuring apparatus capable of precisely measuring grain size of fine particles.SOLUTION: A particle measuring apparatus 100 is an apparatus for measuring particles which includes: a light projection element 111; a light receiving element 112; and a particle detection sensor 110 that detects particles contained in the atmospheric air by receiving scattered light of light from the light projection element 111 which are scattered by the particles in a detection area DA with the light receiving element 112. The particle measuring apparatus 100 also includes: a storage section 140 that stores a correction coefficient corresponding to the sensitivity of the particle detection sensor 110; a IV conversion section 121 that generates a voltage signal by converting a current output from the light receiving element 112 into a voltage; an amplifier 122 that amplifies a voltage signal in a predetermined bandwidth; an AD conversion section 161 that samples and quantizes the voltage signal amplified by the amplifier 122; and a calculation unit 162 that calculates grain size of particles by using a time-series digital data which is a voltage signal sampled and quantized by the AD conversion section 161 and the correction coefficient.

Description

  The present invention includes a particle detecting sensor that includes a light projecting element and a light receiving element, and that detects particles contained in the atmosphere by receiving the scattered light of the light of the light projecting element due to the particles in the detection region by the light receiving element. It relates to a measuring device.

  The light scattering particle measuring device is a particle measuring device having a photoelectric particle detection sensor composed of a light projecting element and a light receiving element, and takes in a gas to be measured and irradiates the light of the light projecting element to the gas. The presence / absence and particle size of particles contained in the gas are detected by the scattered light. For example, particles such as dust, pollen, and smoke floating in the atmosphere can be detected.

  As this type of light scattering type particle detection sensor, a sensor provided with a light trap at a position facing a light projecting element or a light receiving element is known in order to reduce the generation of stray light (see, for example, Patent Document 1). .

Japanese Patent Laid-Open No. 11-248629

  However, such a particle detection sensor may have different characteristics for each individual. In such a case, even if the same gas is introduced, the detection results of the plurality of particle detection sensors may vary due to characteristic variations. That is, it is difficult to accurately measure the particle size of particles using such a particle detection sensor.

  This invention is made | formed in view of such a subject, and it aims at providing the particle | grain measuring apparatus which can measure the particle size of the particle | grains contained in gas accurately.

  To achieve the above object, a particle measuring apparatus according to an aspect of the present invention includes a light projecting element and a light receiving element, and receives light scattered by the light projecting element due to particles in a detection region by the light receiving element. A particle measuring device including a particle detection sensor that detects particles contained in the atmosphere by the storage unit storing a correction coefficient corresponding to the sensitivity of the particle detection sensor, and output from the light receiving element An IV converter that generates a voltage signal by converting the obtained current into a voltage, an amplifier that amplifies the voltage signal in a predetermined band, an AD converter that samples and quantizes the amplified voltage signal, An arithmetic unit that calculates the particle size of the particles using time-series digital data that is the voltage signal sampled and quantized by the AD converter and the correction coefficient.

  The correction coefficient may be a value calculated based on a current output from the light receiving element when standard particles having a predetermined particle diameter are introduced into the detection region.

  The calculation unit may correct a threshold for calculating the particle size of the particles by the correction coefficient, and calculate the particle size of the particles using the corrected threshold.

  The calculation unit may correct the digital data with the correction coefficient and calculate the particle size of the particles using the corrected digital data.

  According to the present invention, the particle size of particles contained in a gas can be accurately measured.

FIG. 1 is a block diagram illustrating an example of a configuration of a particle measuring apparatus according to an embodiment. FIG. 2A is a cross-sectional view for explaining the operation of the particle detection sensor when particles are not present in the atmosphere. FIG. 2B is a cross-sectional view for explaining the operation of the particle detection sensor when particles having a small particle diameter exist in the atmosphere. FIG. 2C is a cross-sectional view for explaining the operation of the particle detection sensor when particles having a large particle diameter exist in the atmosphere. FIG. 3 is a graph showing the light intensity detected by the light receiving element. FIG. 4 is a block diagram for explaining a correction coefficient initial setting process (write process) to the storage unit in the manufacturing process. FIG. 5 is a flowchart showing a correction coefficient initial setting process executed by the writing unit in the manufacturing process. FIG. 6 is a graph for explaining the correction coefficient calculated by the writing unit. FIG. 7 is a flowchart showing a particle size calculation process executed by the calculation unit.

  Below, the particle | grain measuring apparatus which concerns on embodiment of this invention is demonstrated in detail using drawing. Note that each of the embodiments described below shows a preferred specific example of the present invention. Therefore, the numerical values, shapes, materials, components, component arrangements, connection forms, and the like shown in the following embodiments are merely examples, and are not intended to limit the present invention. Therefore, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims showing the highest concept of the present invention are described as optional constituent elements.

  Each figure is a mimetic diagram and is not necessarily illustrated strictly. Moreover, in each figure, the same code | symbol is attached | subjected about the same structural member.

(Embodiment)
[1. Overall configuration of particle measuring apparatus]
First, the whole structure of the particle | grain measuring apparatus which concerns on embodiment of this invention is demonstrated. FIG. 1 is a block diagram showing an example of the configuration of the particle measuring apparatus according to the present embodiment.

  As shown in the figure, the particle measuring apparatus 100 includes a particle detection sensor 110, an analog signal processing unit 120, a sensor module 150 including a power supply unit 130, and a general-purpose MPU (Micro Processing Unit) 160, and is in the atmosphere. The particle size of the contained particles is measured.

  Hereinafter, each structure of the particle | grain measuring apparatus 100 is demonstrated concretely.

[1-1. Configuration of particle detection sensor]
The particle detection sensor 110 is a photoelectric sensor including a light projecting element 111 and a light receiving element 112, and the light receiving element 112 receives scattered light of light from the light projecting element 111 due to particles in the detection area DA. The particle | grains contained in are detected. The particle detection sensor 110 in the present embodiment further includes a reflector 114 having a reflecting surface and a heating unit 115 that heats the atmosphere.

  The light projecting element 111 is a light source (light emitting unit) that emits light of a predetermined wavelength, and is, for example, a solid light emitting element such as an LED or a semiconductor laser. As the light projecting element 111, a light emitting element that emits infrared light, blue light, green light, red light, or ultraviolet light can be used.

  In addition, it becomes easy to detect a particle | grain with a small particle size, so that the light emission wavelength of the light projection element 111 is short. The light emission control method of the light projecting element 111 is not particularly limited, and the light emitted from the light projecting element 111 can be continuous light or pulsed light by DC driving. Moreover, the magnitude | size of the output of the light projection element 111 may be changing temporally.

  The light receiving element 112 is a light receiving unit that receives light, and is an element (photodetector) that receives light and converts it into an electrical signal, such as a photodiode, a photo IC diode, a phototransistor, or a photomultiplier tube. Specifically, the light receiving element 112 generates a current signal as an electrical signal. That is, the light receiving element 112 outputs a current signal corresponding to the received light intensity.

  The light projecting element 111 and the light receiving element 112 are operated by the power supplied from the power supply unit 130.

  As shown in FIG. 1, the light projecting element 111 and the light receiving element 112 are arranged in a housing 113. The housing 113 is configured to hold the light projecting element 111 and the light receiving element 112. In the present embodiment, the light projecting element 111 and the light receiving element 112 are arranged in the housing 113 so that their optical axes intersect each other.

  The housing 113 is provided with a particle flow path that is a cylindrical space region through which air (gas) containing particles flows.

  The detection area DA is an aerosol detection area (aerosol measurement unit) that is an area for detecting particles (aerosol) contained in the gas to be measured. The detection area DA is projected with a space area where light from the light projecting element 111 is projected. This is a spatial region that overlaps the spatial region for guiding the scattered light generated when the light of the optical device 111 hits the particles to the light receiving device 112. The detection area DA is set so as to exist in the particle flow path, and the gas to be measured is guided to the detection area DA through the particle flow path.

  In the present embodiment, the flow direction of the particle flow path (the direction in which the gas to be measured flows) is the vertical direction on the paper surface of FIG. 1, but may be the vertical direction on the paper surface of FIG. That is, in the present embodiment, the flow channel axis of the particle flow channel is set to exist on a plane through which each optical axis of the light projecting element 111 and the light receiving element 112 passes, but is orthogonal to the plane. May be set.

  The reflector 114 (reflecting plate) is a reflecting member that reflects scattered light of the light projecting element 111 due to particles in the detection area DA and guides the scattered light to the light receiving element 112. In the present embodiment, the reflector 114 reflects the scattered light of the particles and collects it on the light receiving element 112. More specifically, the reflector 114 reflects the scattered light of the particles toward the light receiving element 112.

  As the reflector 114, the base member itself may be made of a reflective material such as metal so that the surface of the base member itself becomes a reflective surface, or a reflective film that becomes a reflective surface on the surface of a resin or metal base member May be formed.

As the reflection film, a metal reflection film such as aluminum, gold, silver or copper, a mirror reflection film, a dielectric multilayer film, or the like can be used. As the reflective film, a film having a low absorptance and a high reflectance is preferable. Moreover, you may use as a reflecting film what laminated | stacked the thin film thinner than the said aluminum film on the surface of the aluminum film formed by vapor deposition. As the thin film laminated on the aluminum film, for example, an MgF film, a SiO ₂ film, a SiO film, an AlN film, an alumina film, an enhanced reflection film, or the like is used. Thus, by laminating these thin films on the aluminum film, it is possible to suppress deterioration (corrosion and the like) of the aluminum film and improve optical characteristics by optical amplification.

  The heating unit 115 heats the atmosphere in order to introduce the atmosphere containing particles into the detection area DA, and functions as an airflow generation device that generates an airflow for promoting the flow of the gas flowing in the particle flow path. . Specifically, the heating unit 115 is a low-cost heater resistor or the like, and is disposed in the particle channel in the present embodiment. That is, the heating unit 115 heats the atmosphere in the particle channel.

  For example, when the heating unit 115 is a heater resistor, the heater resistor is heated when a voltage is applied to the heater resistor. As a result, the atmosphere around the heater resistor is heated to decrease the density, and moves upward in the direction opposite to gravity. That is, when the air in the particle flow path is heated by the heating unit 115, an upward air flow (upward air flow) can be generated.

  Thus, by heating the atmosphere in the particle flow path by the heating unit 115, the measurement target gas (atmosphere) can be easily drawn into the housing 113 (particle flow path). More particles can be taken into the particle detection sensor 110 than when not provided. Therefore, since the amount of particles per unit volume in the detection area DA included in the particle flow path can be increased, the sensitivity can be increased.

  Moreover, since the heating unit 115 generates an upward air flow, it is preferable to install the heating unit 115 in a lower part of the particle channel as shown in FIG. Even when the heating unit 115 is not operating, the atmosphere can pass through the particle flow path. That is, even when the heating unit 115 is not operating, it is possible to detect particles contained in the atmosphere.

[1-2. Operation of particle detection sensor]
Next, the operation of the particle detection sensor 110 in this embodiment will be described with reference to FIGS. 2A, 2B, 2C, and 3. FIG. 2A to 2C show the operation of the particle detection sensor 110 when there are no particles in the atmosphere, when particles with a small particle diameter exist in the atmosphere, and when particles with a large particle diameter exist in the atmosphere, respectively. It is sectional drawing for demonstrating. FIG. 3 is a graph showing the light intensity detected by the light receiving element 112 in the state shown in FIGS. 2A to 2C.

  When the heating unit 115 is operated to generate an air flow in the particle passage, the atmosphere is drawn into the particle detection sensor 110 from the atmosphere introduction hole, and the atmosphere is guided to the detection area DA via the particle passage.

  In this case, as shown in FIG. 2A, when there is no particle (aerosol) in the atmosphere introduced into the particle detection sensor 110, that is, when the particle does not flow into the detection area DA, the light is emitted from the light projecting element 111. Since the light passes straight through the detection area DA, light scattered by particles is not generated. Therefore, in this case, basically, there is no reaction of the light receiving element 112, so that it can be seen that there are no particles in the atmosphere introduced into the particle detection sensor 110.

  In this case, light traveling straight through the detection area DA may be reflected in the housing 113 and enter the light receiving element 112 as stray light. However, in this case, the light intensity detected by the light receiving element 112 is smaller than when the particles are present in the detection area DA. Therefore, it can be seen that there are no particles in the atmosphere introduced into the particle detection sensor 110.

  In addition, as shown in FIG. 2B, when there is a particle (aerosol) P1 having a small particle size in the atmosphere introduced into the particle detection sensor 110, that is, when a particle P1 having a small particle size flows into the detection area DA. The light of the light projecting element 111 strikes the particle P1 existing in the detection area DA and is scattered, and the scattered light is reflected directly or by the reflector 114 and enters the light receiving element 112.

  Specifically, in this case, scattered light having a light intensity as indicated by “particle size: small” in FIG. Here, as described above, the light receiving element 112 outputs a current signal corresponding to the received light intensity. Therefore, in this case, the current signal output from the light receiving element 112 is relatively small. Thereby, it can be seen that particles having a small particle diameter exist in the atmosphere introduced into the particle detection sensor 110.

  In addition, as shown in FIG. 2C, when particles (aerosol) P2 having a large particle size exist in the atmosphere introduced into the particle detection sensor 110, that is, when particles P2 having a large particle size flow into the detection area DA. The light of the light projecting element 111 strikes the particles P2 existing in the detection area DA and is scattered, and the scattered light is reflected directly or by the reflector 114 and enters the light receiving element 112.

  Specifically, in this case, scattered light having a light intensity as indicated by “particle size: large” in FIG. Therefore, in this case, the current signal output from the light receiving element 112 is relatively large. Thus, it can be seen that particles P2 having a large particle size exist in the atmosphere introduced into the particle detection sensor 110.

  In this way, the particle detection sensor 110 can detect whether or not particles are included in the atmosphere introduced into the particle detection sensor 110 (the presence or absence of particles). That is, particles in the atmosphere can be detected. Further, when particles are included in the atmosphere, a current signal corresponding to the particle size of the particles is output.

[1-3. Configuration of analog signal processor]
The analog signal processing unit 120 performs various signal processing on the current signal output from the particle detection sensor 110 to output an analog voltage signal based on the current signal. Here, various signal processing includes, for example, I / V conversion for converting current (I) into voltage (V), bandpass filter processing for passing a desired frequency band of an input signal, and input. Amplification processing for amplifying and outputting the received signal.

  The analog signal processing unit 120 is not limited to the processes exemplified here, and may perform other signal processing (for example, high-pass filter processing, low-pass filter processing, attenuation processing, and the like).

  As illustrated in FIG. 1, the analog signal processing unit 120 includes an IV conversion unit 121 and an amplification unit 122.

[1-3-1. IV conversion unit]
The IV converter 121 converts the current output from the light receiving element 112 into a voltage (IV conversion). That is, the IV conversion unit 121 converts the current signal output from the particle detection sensor 110 into a voltage signal. By converting the voltage signal in this way, the design of the amplifying unit 122 connected to the subsequent stage of the IV converting unit 121 is facilitated.

[1-3-2. Amplification unit]
The amplification unit 122 amplifies a predetermined band of the voltage signal converted by the IV conversion unit 121. Specifically, a frequency component in a predetermined band among frequency components included in the voltage signal is amplified with a higher amplification factor than frequency components in other bands. Here, the predetermined band is, for example, a band having a frequency f1 corresponding to the flow velocity v1 of the atmosphere flowing in the particle flow path of the particle detection sensor 110 as a center frequency and a bandwidth as fbw. Note that fbw may be a predetermined frequency, or may be a frequency that is appropriately set according to the noise floor of the voltage signal. In other words, the amplification unit 122 amplifies the voltage signal converted by the IV conversion unit 121 and converts it to a voltage signal including a pulse waveform corresponding to the particle.

  For example, as illustrated in FIG. 1, the amplifying unit 122 includes a band-pass filter 122 a that passes a frequency component in a predetermined band among frequency components included in the voltage signal output from the IV conversion unit 121, and a band-pass filter. And an amplifier 122b that amplifies a signal composed of frequency components that have passed through 122a. Note that the connection order of the bandpass filter 122a and the amplifier 122b is not limited to this, and the amplifier 122b may be provided upstream of the bandpass filter 122a.

  With such a configuration, the analog signal processing unit 120 outputs a voltage signal based on the current signal output from the particle detection sensor 110.

[1-4. Power supply part]
The power supply unit 130 supplies power to the components (particle detection sensor 110 and analog signal processing unit 120) other than the power supply unit 130 among the configurations included in the sensor module 150. The power supply unit 130 is configured by, for example, a regulator that converts a voltage supplied from the outside of the sensor module 150 into a desired voltage.

[1-5. Storage unit]
The storage unit 140 is, for example, a memory that stores a correction coefficient corresponding to the sensitivity of the particle detection sensor 110. Specifically, a correction coefficient corresponding to the sensitivity of the particle detection sensor 110 mounted on the sensor module 150 on which the storage unit 140 is mounted is stored.

  Here, the correction coefficient is, for example, a value calculated based on the current output from the light receiving element 112 when standard particles having a predetermined particle diameter are introduced into the detection area DA. This correction coefficient is generated by being written in the manufacturing process of the particle measuring apparatus 100. In other words, the correction coefficient is initially set in the manufacturing process of the particle measuring apparatus 100. The correction coefficient initial setting process in the manufacturing process will be described later.

[2. General-purpose MPU configuration]
The general-purpose MPU 160 uses the analog voltage signal output from the analog signal processing unit 120 to calculate the particle size of particles contained in the atmosphere flowing in the particle flow path of the particle detection sensor 110. This general-purpose MPU 160 is realized by, for example, a system LSI that is an integrated circuit, and may be individually made into one chip for each configuration described below, or may be made into one chip so as to include some or all of them. .

  The general-purpose MPU 160 is not limited to the system LSI, and may be realized by a dedicated circuit or a general-purpose processor. An FPGA (Field Programmable Gate Array) that can be programmed after manufacturing the LSI or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used.

  As shown in FIG. 1, such a general-purpose MPU 160 includes an AD conversion unit 161, and is included in the air flowing in the particle flow path of the particle detection sensor 110 using the digital data generated by the AD conversion unit 161. Various analyzes can be performed on the particles to be collected. The various analyzes include, for example, calculation of the particle diameter of the particle or identification of the particle.

  In the present embodiment, the general-purpose MPU 160 further includes a calculation unit 162 as shown in FIG. Hereinafter, each configuration of the general-purpose MPU 160 will be described.

[2-1. AD converter]
The AD conversion unit 161 samples (samples) and quantizes the voltage signal amplified by the amplification unit 122. In other words, the AD converter 161 generates time-series digital data corresponding to the voltage signal by performing AD (Analog to Digital) conversion on the analog voltage signal output from the analog signal processor 120. That is, the AD conversion unit 161 generates time-series digital data based on the current signal output from the particle detection sensor 110.

  Specifically, the AD conversion unit 161 is an AD conversion module incorporated in advance in the general-purpose MPU 160, and converts a voltage signal input to an analog input terminal of the general-purpose MPU 160 into digital data. For example, the AD conversion unit 161 samples a voltage signal in a range of 0.0 to 5.0 V input to a terminal set for analog input in the general-purpose MPU 160 at a predetermined sampling period, and the sampled voltage signal Is converted into a 10-bit digital value to generate digital data.

  The range of the voltage input to the analog input terminal of the general-purpose MPU 160 is not limited to the above example. For example, the maximum value of the input voltage is a voltage specified from the outside of the general-purpose MPU 160 (eg, 3.3 V). It may be. Further, the number of bits of digital data generated by the AD conversion unit 161 is not limited to the above example, and may be, for example, 8 bits or 12 bits.

[2-2. Calculation unit]
The calculation unit 162 calculates the particle size of particles contained in the gas flowing in the particle flow path of the particle detection sensor 110 using the digital data generated by the AD conversion unit 161.

  Here, the calculating part 162 demonstrates the outline | summary of the calculation process of the particle size of the particle | grains by the calculating part 162. FIG.

  As described above, the current signal output from the particle detection sensor 110 is a signal corresponding to the particle size of particles contained in the gas flowing in the particle flow path of the particle detection sensor 110. Therefore, the digital data input from the AD conversion unit 161 to the calculation unit 162 also has a size corresponding to the particle size of the particles. Specifically, since the current signal increases as the particle size of the particle increases, the digital data also increases as the particle size of the particle increases.

  However, the particle detection sensor 110 may have different characteristics for each individual. In such a case, even if the same gas is introduced into the particle flow path of each particle detection sensor 110, the current signal output from each particle detection sensor 110 may vary due to characteristic variations. There is. Such a variation in the current signal corresponds to a variation in sensitivity of the plurality of particle detection sensors 110.

  Therefore, in the present embodiment, in the particle size calculation process by the calculation unit 162, the particle size of the particle is calculated using the digital data generated by the AD conversion unit 161 and the correction coefficient stored in the storage unit 140. (Calculate).

  Thereby, the particle | grain measuring apparatus 100 which concerns on this Embodiment can reduce the influence by the sensitivity of the particle | grain detection sensor 110, and can calculate a particle size. That is, the particle size of particles contained in the atmosphere can be calculated with high accuracy.

  Specifically, in the present embodiment, calculation unit 162 corrects the threshold value for calculating the particle size of the particle using a correction coefficient, and calculates the particle size of the particle using the corrected threshold value. The details of the particle size calculation process performed by the calculation unit 162 will be described later.

[3. Highly accurate measurement of particle size]
Hereinafter, the fact that the particle measuring apparatus 100 according to the present embodiment can measure the particle diameter of particles contained in the air with high accuracy will be described in detail with reference to the correction coefficient initial setting process and the particle diameter calculation process.

[3-1. Correction coefficient initialization process]
First, correction coefficient initial setting processing for the storage unit 140 will be described with reference to FIGS. As described above, this correction coefficient is written in the manufacturing process of the particle measuring apparatus 100, for example.

  FIG. 4 is a block diagram for explaining correction coefficient initial setting processing (writing processing) to the storage unit 140 in the manufacturing process of the particle measuring apparatus 100 according to the present embodiment.

  As shown in the figure, in the manufacturing process, the correction coefficient is written into the storage unit 140 by the writing unit 500 connected to the sensor module 150 on which the storage unit 140 is mounted.

  The writing unit 500 calculates a correction coefficient corresponding to the sensitivity of the particle detection sensor 110 based on the current output from the light receiving element 112 when standard particles having a predetermined particle diameter are introduced into the detection area DA. Correct the value. Further, the writing unit 500 writes the calculated correction coefficient in the storage unit 140.

  Hereinafter, the correction coefficient initial setting processing by the writing unit 500 will be described with reference to FIGS. 5 and 6. FIG. 5 is a flowchart showing correction coefficient initial setting processing executed by the writing unit 500 in the manufacturing process. FIG. 6 is a graph for explaining the correction coefficient calculated by the writing unit 500.

  First, the writing unit 500 introduces standard particles having a predetermined particle size into the particle flow path of the particle detection sensor 110 of the particle detection sensor 110 (S11). That is, the standard particles are introduced into the detection area DA. The introduction of the standard particles may not be performed by the writing unit 500, and may be realized by arranging the particle detection sensor 110 in a chamber filled with a gas containing standard particles.

  Next, the writing unit 500 acquires a peak value based on the current output from the particle detection sensor 110 in a state where the standard particles are introduced (S12). Specifically, the writing unit 500 acquires the peak value of the voltage output from the sensor module 150.

  For example, when the voltage signal output from the sensor module 150 is indicated by the first acquisition waveform in FIG. 6, the writing unit 500 acquires the peak value P1 of the first acquisition waveform. Similarly, when the voltage waveform is as shown by the second acquired waveform in FIG. 6, the peak value P2 of the second acquired waveform is acquired.

  Next, the writing unit 500 calculates a correction coefficient based on the acquired peak value (S13), and writes the calculated correction coefficient in the storage unit 140 (S14).

  Here, in the correction coefficient calculation process (S13), the writing unit 500 specifically calculates the correction coefficient fk using the acquired peak value and a predetermined ideal peak value PI.

  For example, the writing unit 500 calculates a value obtained by dividing the ideal peak value PI by the peak value of the voltage signal output from the sensor module 150 as the correction coefficient fk.

  That is, when the voltage signal output from the sensor module 150 is the first acquisition waveform in FIG. 6, that is, when the peak value acquired in the peak value acquisition process (S12 described above) is P1, the writing unit 500 performs PI. / P1 is calculated as the correction coefficient fk. Thereby, when the voltage signal output from the sensor module 150 is relatively small, a value larger than 1 is calculated as the correction coefficient fk.

  Similarly, for example, in the case where the voltage signal output from the sensor module 150 is the second acquired waveform in FIG. 6, the writing unit 500 has a peak value acquired in the peak value acquisition process (S12 above) of P2. In this case, PI / P2 is calculated as the correction coefficient fk. Thereby, when the voltage signal output from the sensor module 150 is relatively large, a value smaller than 1 is calculated as the correction coefficient fk.

  Here, as described above, the voltage signal output from the sensor module 150 corresponds to the current output from the particle detection sensor 110, and the current corresponds to the sensitivity of the particle detection sensor 110. Therefore, the ideal peak value PI and the actual peak value correspond to the reference sensitivity that is a reference for the sensitivity of the particle detection sensor 110 and the actual sensitivity of the particle detection sensor 110.

  Therefore, when the voltage signal output from the sensor module 150 is relatively small, that is, when the sensitivity is low, the writing unit 500 calculates a value larger than 1 as the correction coefficient fk. On the other hand, when the voltage signal output from the sensor module 150 is relatively large, that is, when the sensitivity is high, a value smaller than 1 is calculated as the correction coefficient fk. By calculating the correction coefficient fk according to the sensitivity of the particle detection sensor 110 as described above, it is possible to calculate the particle size while reducing the influence of the sensitivity of the particle detection sensor 110 in the particle size calculation processing described later. .

  Thus, the writing unit 500 writes the correction coefficient fk corresponding to the sensitivity of the particle detection sensor 110 with respect to the reference sensitivity in the storage unit 140.

  Here, the “ideal peak value” is, for example, a peak value of an ideal waveform output from the sensor module 150 including the particle detection sensor 110 when standard particles are introduced into the detection area DA of the particle detection sensor 110. It is. For example, when the ideal waveform is a waveform as shown in FIG. 6, the ideal peak value is PI.

  The ideal peak value is not limited to the value determined by the ideal waveform, and may be determined by the design value of the sensor module 150 including the particle detection sensor 110, for example. Further, for example, when standard particles are introduced into the detection area DA of each particle detection sensor 110 of the plurality of sensor modules 150, the average value or median value of the peak values of the voltage signals output from the plurality of sensor modules 150 Etc.

  Through the initial setting process as described above, the correction coefficient fk corresponding to the sensitivity of the particle detection sensor 110 with respect to the reference sensitivity is written in the storage unit 140.

  Therefore, in the particle size calculation process by the calculation unit 162, the particle size of the particle is calculated using the correction coefficient fk calculated in this way, thereby reducing the influence of the sensitivity of the particle detection sensor 110, thereby reducing the particle size. Can be calculated. That is, the particle size of particles contained in the atmosphere can be calculated with high accuracy.

[3-2. Particle size calculation process]
Next, particle size calculation processing (calculation processing) by the calculation unit 162 will be described with reference to FIG. As described above, the calculation unit 162 of the particle measurement device 100 calculates the particle size of the particles using the correction coefficient written in the storage unit 140 in the manufacturing process of the particle measurement device 100. FIG. 7 is a flowchart showing a particle size calculation process executed by the calculation unit 162.

  First, the calculation unit 162 reads the correction coefficient fk from the storage unit 140 (S21).

  Thereafter, the calculation unit 162 corrects the threshold value for calculating the particle diameter of the particles by the correction coefficient fk (S22), and calculates (calculates) the particle diameter using the corrected threshold value (S23).

  For example, when the particle size is calculated using the 10-step threshold values Vth1 to Vth10, the calculation unit 162 has a range in which the peak value of the digital data generated by the AD conversion unit 161 is divided by the 10-step threshold values Vth1 to Vth10. The particle size is calculated by determining where it is located.

  Here, the digital data generated by the AD conversion unit 161 is a value depending on the sensitivity of the particle detection sensor 110. That is, even when particles having the same particle diameter are introduced, if the sensitivity of the particle detection sensor 110 is high, the value of the digital data becomes a relatively large value, whereas the sensitivity of the particle detection sensor 110 is low. The value of digital data is a relatively small value.

  Therefore, when the particle size of the particles is calculated using the same threshold values Vth1 to Vth10 regardless of the sensitivity of the particle detection sensor 110, the following problem may occur.

  Specifically, when the sensitivity of the particle detection sensor 110 is low, the particle size calculated by the calculation unit 162 may be calculated smaller than the actual particle size. On the other hand, when the sensitivity of the particle detection sensor 110 is high, the particle size calculated by the calculation unit 162 may be calculated larger than the actual particle size.

  As described above, when the calculation unit 162 calculates the particle size without correcting the threshold values Vth1 to Vth10, it may be difficult to calculate the particle size with high accuracy.

  On the other hand, in the present embodiment, the arithmetic unit 162 corrects the threshold values Vth1 to Vth10 using the correction coefficient fk stored in the storage unit 140 in the correction process (S22). Thereafter, in the particle size calculation process (S23), the particle size of the particles is calculated using the corrected threshold values Vth1 'to Vth10'. For example, the calculation unit 162 calculates the particle size using the values obtained by multiplying the correction coefficients fk stored in the storage unit 140 by the threshold values Vth1 to Vth10 before correction as the threshold values Vth1 'to Vth10' after correction.

  Thereby, the calculating part 162 can reduce the influence by the sensitivity of the particle | grain detection sensor 110, and can calculate a particle size. That is, the particle size of the particles can be calculated with high accuracy. That is, by the particle diameter calculation process as described above, the particle measuring apparatus 100 according to the present embodiment can accurately calculate the particle diameter of particles contained in the gas flowing in the particle flow path of the particle detection sensor 110. .

  Furthermore, the calculation unit 162 can calculate the particle diameter of the particles with high accuracy by a simple process that only corrects the threshold values Vth1 to Vth10. Therefore, the particle size of the particles can be calculated with high accuracy without using a high-performance device as the general-purpose MPU 160.

[4. Summary]
As described above, the particle measuring apparatus 100 according to the present embodiment converts the current output from the storage unit 140 storing the correction coefficient fk according to the sensitivity of the particle detection sensor 110 and the light receiving element 112 into a voltage. An IV converter 121 for generating a voltage signal, an amplifier 122 for amplifying the voltage signal, an AD converter 161 for sampling and quantizing the amplified voltage signal, and sampling and quantization by the AD converter 161 A calculation unit 162 that calculates the particle size of the particles using the time-series digital data that is the voltage signal and the correction coefficient fk.

  Thereby, the calculating part 162 can reduce the influence by the sensitivity of the particle | grain detection sensor 110, and can calculate a particle size. Therefore, the particle measuring apparatus 100 according to the present embodiment can calculate the particle diameter of the particles contained in the gas flowing in the particle flow path of the particle detection sensor 110 with high accuracy.

  In the present embodiment, the correction coefficient fk is a value calculated based on the current output from the light receiving element 112 when standard particles having a predetermined particle diameter are introduced into the detection region.

  In the present embodiment, the calculation unit 162 corrects the threshold value for calculating the particle size of the particle using the correction coefficient fk, and calculates the particle size of the particle using the corrected threshold value.

  As described above, in the present embodiment, the particle diameter of the particles contained in the gas flowing in the particle flow path of the particle detection sensor 110 can be accurately calculated by a simple process that only corrects the threshold value.

  In addition, the calculation unit 162 may always perform the above-described particle size calculation process (S23), that is, calculation (peak search) for detecting the peak value of the digital data, or when a predetermined condition is satisfied. May only go to.

  For example, the calculation unit 162 may perform a peak search when the digital data generated by the AD conversion unit 161 is larger than the lowest threshold value (for example, Vth1 ′) among the corrected threshold values Vth1 ′ to Vth10 ′. . In other words, the arithmetic unit 162 may start the peak search when the digital data exceeds the corrected minimum threshold value Vth1 '.

  As described above, the calculation unit 162 can reduce the calculation amount (processing amount) by performing the peak search only when a predetermined condition is satisfied, as compared with the case of performing the constant peak search. That is, the particle size of the particles can be calculated without using a high-performance device as the general-purpose MPU 160.

  Here, the corrected minimum threshold value Vth1 'may be a value larger than a digital value corresponding to the noise floor of the voltage signal input to the AD conversion unit 161.

  Thereby, the various misdetections which arise when the calculating part 162 calculates the peak of a noise can be reduced. Note that various misdetections include, for example, misdetection of the particle diameter of particles and misdetection of the number of particles.

  Note that the timing for starting the peak search is not limited to the timing when the digital data generated by the AD converter 161 exceeds the minimum threshold value Vth1 ′ after correction, but is the timing when the digital data generated by the AD converter 161 exceeds the minimum threshold value Vth1 before correction. May be.

(Modification)
Next, a modified example of the above embodiment will be described focusing on differences from the above embodiment.

  In the embodiment described above, the calculation unit 162 corrects the threshold value for calculating the particle diameter of the particle using the correction coefficient, and calculates the particle diameter of the particle using the corrected threshold value. On the other hand, in the present modification, the calculation unit 162 corrects the digital data generated by the AD conversion unit 161 with the correction coefficient, and calculates the particle size of the particles using the corrected digital data.

  Hereinafter, the particle size calculation process (calculation process) by the calculation unit 162 in this modification will be described. The calculation process is almost the same as the particle diameter calculation process in the above-described embodiment described with reference to FIG. 7, but the processes in the correction process (S22) and the particle diameter calculation process (S23) are different.

  Specifically, the calculation unit 162 in the present modification corrects the digital data generated by the AD conversion unit 161 in the correction process (S22).

  Here, as described above, the digital data generated by the AD conversion unit 161 is a value depending on the sensitivity of the particle detection sensor 110. That is, even when particles having the same particle diameter are introduced, if the sensitivity of the particle detection sensor 110 is high, the value of the digital data becomes a relatively large value, whereas the sensitivity of the particle detection sensor 110 is low. The value of digital data is a relatively small value.

  Specifically, as described above, when the sensitivity of the particle detection sensor 110 is low, the particle size calculated by the calculation unit 162 may be calculated smaller than the actual particle size. On the other hand, when the sensitivity of the particle detection sensor 110 is high, the particle size calculated by the calculation unit 162 may be calculated larger than the actual particle size.

  Therefore, when the calculation unit 162 in this modification calculates the particle size without correcting the digital data, it may be difficult to calculate the particle size with high accuracy.

  On the other hand, in the present modification, the calculation unit 162 corrects the digital data and calculates the particle size of the particles using the corrected digital data. For example, the calculation unit 162 calculates the particle size using data obtained by multiplying the correction coefficient fk stored in the storage unit 140 by digital data before correction as digital data after correction.

  That is, the calculation unit 162 in the present modification corrects the digital data to be larger when the sensitivity of the particle detection sensor 110 mounted on the particle measuring device 100 is low. On the other hand, when the sensitivity of the particle detection sensor 110 mounted on the particle measuring apparatus 100 is high, the digital data is corrected to be small.

  Thereby, the calculating part 162 in this modification produces the same effect as the said embodiment. That is, the particle size can be calculated while reducing the influence of the sensitivity of the particle detection sensor 110. That is, the particle size of the particles can be calculated with high accuracy.

  Here, as a configuration for accurately calculating the particle size of the particle by reducing the influence of the sensitivity of the particle detection sensor 110, a configuration in which the amplification factor of the amplification unit 122 is changed according to the sensitivity of the particle detection sensor 110 is considered. It is done. As such a configuration, for example, a configuration in which the circuit constant of the amplifier 122b is designed to be adjustable with a variable resistor or the like, and the circuit constant is adjusted according to the sensitivity of the particle detection sensor 110 is conceivable.

  However, when the circuit constant of an analog circuit such as the amplifier 122b is adjusted, the temperature coefficient of the circuit constant may be different before and after the adjustment. That is, depending on the sensitivity of the particle detection sensor 110, the temperature dependence of the circuit constant of the analog circuit may be different.

  On the other hand, in this modification, digital data is corrected according to the sensitivity of the particle detection sensor 110. Therefore, the temperature dependence of the circuit constant of the analog circuit can be made substantially the same regardless of the sensitivity of the particle detection sensor 110.

  Furthermore, when adjusting the circuit constants of an analog circuit such as the amplifier 122b, the long-term reliability of the particle measuring device may be lowered. This is because the analog circuit has a large long-term performance drift due to vibration or moisture absorption of circuit elements constituting the analog circuit.

  On the other hand, in this modification, digital data is corrected according to the sensitivity of the particle detection sensor 110. Therefore, long-term performance drift of the analog circuit can be suppressed, and long-term reliability can be ensured.

  In addition, the calculation unit 162 may always perform the above-described particle size calculation process (S23), that is, calculation (peak search) for detecting the peak value of the digital data, or when a predetermined condition is satisfied. May only go to.

  For example, when the digital data after correction is larger than the lowest threshold value (for example, Vth1) among a plurality of threshold values (for example, threshold values Vth1 to Vth10 in 10 steps) for calculating the particle diameter, A peak search may be performed. In other words, the arithmetic unit 162 may start the peak search when the digital data exceeds the minimum threshold value.

  As described above, the calculation unit 162 can reduce the calculation amount (processing amount) by performing the peak search only when a predetermined condition is satisfied, as compared with the case of performing the constant peak search. That is, the particle size of the particles can be calculated without using a high-performance device as the general-purpose MPU 160.

  Here, the lowest threshold value Vth1 may be a value larger than a value obtained by correcting the digital value corresponding to the noise floor of the voltage signal input to the AD converter 161 with the correction coefficient fk.

  Thereby, the various misdetections which arise when the calculating part 162 calculates the peak of a noise can be reduced. Note that various misdetections include, for example, misdetection of the particle diameter of particles and misdetection of the number of particles.

  Note that the timing for starting the peak search is not limited to the timing when the corrected digital data exceeds the minimum threshold value Vth1, but may be the timing when the digital data before correction exceeds the minimum threshold value Vth1.

(Other variations)
As mentioned above, although the particle | grain measuring apparatus was demonstrated based on embodiment and modification about this invention, this invention is not limited to said embodiment and modification.

  In the above description, the medium containing particles is the atmosphere (air), but may be a medium other than the atmosphere (liquid such as water).

  The configuration of the particle detection sensor 110 is not limited to the configuration described above, and includes at least a light projecting element 111 and a light receiving element 112, and receives light scattered from the light projecting element by particles in the detection area DA. The particles contained in the atmosphere may be detected by receiving the light. Even with such a configuration, the particle measuring apparatus including the particle detection sensor can accurately measure the particle size of particles contained in the gas.

  The configuration of the amplifying unit is not limited to the configuration described above, and at least the voltage signal output from the IV conversion unit 121 may be amplified in a predetermined band. That is, the amplification unit may not include the band pass filter 122a, and may include a high pass filter, a low pass filter, or the like. Further, the amplifier 122b may be a single stage or a plurality of stages.

  In the above description, each component in the general-purpose MPU may be configured by dedicated hardware or may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or a processor reading and executing a software program recorded on a recording medium such as a hard disk or a semiconductor memory.

  The calculation unit is not limited to the above description, and may calculate (calculate) the particle size of the particles using at least digital data and a correction coefficient. For example, the calculation unit obtains the peak value of the digital data, corrects the peak value using the obtained peak value and the correction coefficient fk stored in the storage unit 140, and uses the corrected peak value to determine the particle size of the particles. The diameter may be calculated.

  The correction coefficient is not limited to the one generated by writing in the manufacturing process as described above, and may be generated every time a predetermined time elapses after the particle detection sensor 110 is activated, for example. . As described above, by using the correction coefficient generated after the activation of the particle detection sensor 110, the particle measurement apparatus 100 can suppress deterioration in accuracy of particle size calculation due to deterioration of components constituting the particle detection sensor 110 or the like. .

  In the above description, the correction coefficient stored in the storage unit 140 is based on a value calculated based on the current output from the light receiving element 112 when standard particles are introduced into the detection area DA. Not limited to this. The correction coefficient only needs to correspond to at least the sensitivity of the particle detection sensor 110 mounted on the sensor module on which the storage unit 140 is mounted. For example, the particle detection sensor 110 with respect to the average sensitivity of a plurality of particle detection sensors. May correspond to the sensitivity.

  In addition, any combination of the components and functions in the embodiment and the modification can be arbitrarily combined without departing from the gist of the present invention, and the form obtained by making various modifications conceived by those skilled in the art with respect to the embodiment and the modification. The embodiment realized by the above is also included in the present invention.

  For example, various devices (a smoke detector, an air cleaner, a ventilation fan, or the like) including the particle measuring device according to the above-described embodiment and modification are also included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 100 Particle measuring device 110 Particle | grain detection sensor 111 Light projection element 112 Light receiving element 121 IV conversion part 122 Amplification part 140 Storage part 161 AD conversion part 162 Operation part

Claims (4)

A particle measuring device including a particle detecting sensor, which includes a light projecting element and a light receiving element, and detects particles contained in the atmosphere by receiving the scattered light of the light from the light projecting element due to particles in a detection region by the light receiving element. Because
A storage unit storing a correction coefficient according to the sensitivity of the particle detection sensor;
An IV converter that generates a voltage signal by converting the current output from the light receiving element into a voltage;
An amplifier for amplifying the voltage signal in a predetermined band;
An AD converter for sampling and quantizing the amplified voltage signal;
A particle measuring apparatus comprising: an arithmetic unit that calculates the particle size of the particles using time-series digital data that is the voltage signal sampled and quantized by the AD converter and the correction coefficient. The particle measurement apparatus according to claim 1, wherein the correction coefficient is a value calculated based on a current output from the light receiving element when standard particles having a predetermined particle diameter are introduced into the detection region. The particle measurement according to claim 1, wherein the calculation unit corrects a threshold value for calculating the particle diameter of the particle by the correction coefficient, and calculates the particle diameter of the particle using the corrected threshold value. apparatus. The particle measuring apparatus according to claim 1, wherein the calculation unit corrects the digital data with the correction coefficient, and calculates the particle size of the particles using the corrected digital data.

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