JP4555664B2 - Particle counter - Google Patents

Description

The present invention relates to a particle counting apparatus for continuously detecting the concentration of particles floating in the air.

  Conventionally, the manufacture of precision machines and parts thereof is performed in a clean room. This clean room is provided with a light scattering type particle counter that continuously detects the number (concentration) of suspended particles in the air because the concentration of particles suspended in the internal air needs to be lower than the reference value. .

  The particle counting apparatus includes a particle counting sensor that detects particles contained in the aspirated (sampled) air, and a counting unit that counts the number of particles that have passed through the sensor based on an output pulse of the particle counting sensor. I have.

Among them, the particle counting sensor includes a flow path in which an intake port and an exhaust port communicate with each other, an air introduction unit that introduces air from the intake port into a measurement region of the flow channel and discharges the air from the exhaust port, Light emitting means for irradiating the measurement area with light, light receiving means for receiving scattered light from particles in the air irradiated by the light emitting means, and output for converting the output from the light receiving means into a digital pulse and outputting it Means.

  The diameter of the detected particle can be determined from the peak value of the digital pulse output from the output means. Therefore, a peak value (reference voltage value) corresponding to the particle diameter to be counted is set in advance, and the microcomputer constituting the counting means counts the number of pulses equal to or greater than the reference voltage value, thereby passing the particle diameter to be counted. The above particle number is judged and displayed on the display means.

  Prior art document information related to the particle counter of the present invention includes the following.

JP-A-11-237329

  However, since the conventional particle counting device counts one rectangular pulse as one particle, even when two or more particles simultaneously pass through the measurement region in the sensor, it counts as one particle. End up. Therefore, there is a problem that the detection result smaller than the number of actually sampled particles is displayed on the display means, and the accuracy is lowered.

Here, in order to solve this problem, there is a method of making the measurement region as small as possible. In this case, the air flow path must also be reduced. On the other hand, in the measurement at a low particle concentration such as in a clean room, since the number of floating particles is small, it is necessary to sample a large amount of air for accurate detection. However, when a large amount of air is sampled in a small flow path, the speed of particles passing through the measurement region is increased. Along with this, the output light pulse becomes a weak pulse at a high frequency, and in order to detect it, an expensive light receiving element and an expensive amplifier are required, and the entire device is very expensive. There's a problem.

  In addition, since this type of particle counter detects the number of particles per unit flow rate, it is necessary to accurately sample at a constant flow rate. As a result, it is necessary to use a pump with a stable flow rate, or to use a flow meter in combination so as to ensure a constant flow rate.

  An object of the present invention is to provide an inexpensive particle counter that can detect the number of suspended particles in the air with high accuracy.

In order to solve the above problems, the particle counting apparatus of the present invention guides the introduced air to the measurement region, irradiates the measurement region with light by the light emitting means, and receives the scattered light from the particles contained in the air. And a particle counting sensor for converting the output from the light receiving means into a digital pulse by the output means and outputting the digital pulse, and a counting means for counting the number of particles based on the output pulse from the particle counting sensor. and the particle counting apparatus, the output means of said particle counting sensor comprises a current-voltage conversion circuit for converting the pulse current output from said light receiving means to the pulse voltage, the counting target particles larger than the diameter of which is set in advance When a pulse voltage larger than the reference voltage value is input from the current-voltage conversion circuit due to the passage of particles , it becomes High, and a pulse voltage smaller than the reference voltage value is input. A comparison circuit that outputs a digital pulse that becomes low, and a rectangular wave that outputs a rectangular wave with a pulse width smaller than the pulse width between high and low of the digital pulse when particles with the smallest particle size to be counted pass. And a logical product circuit that outputs a logical product of the comparison circuit and the rectangular wave generation circuit, and the counting unit counts the number of pulses of the rectangular wave input from the logical product circuit of the output unit. The calculated pulse width is compared with the comparison pulse width when a particle having a diameter larger than the minimum counting target particle diameter passes. When the output pulse width is equal to or less than the comparison pulse width, one particle has passed. Counting is performed, and when the output pulse width is larger than the comparison pulse width, it is counted that two particles have passed.

In this particle counter, the minimum particle diameter to be counted is preferably 0.3 microns, and the particle diameter to be counted as the comparison pulse width is preferably 1 micron .

A particle counter of the present invention, instead of counting the number of pulses outputted from the light receiving means via the output unit, a configuration capable of counting the number of 1 or more particles based on the width of the pulse output from the light receiving means Therefore, the counting omission is greatly eliminated and highly accurate counting can be performed. As a result, it is not necessary to reduce the measurement area, and accordingly, an expensive light receiving element and amplifier are not required. In addition, it is not necessary to use an expensive pump or a flow meter in combination to ensure stable air sampling. As a result, a highly accurate and inexpensive particle counter can be provided.

  In addition, since the particle counting sensor used in the apparatus outputs a pulse corresponding to the scattered light detected by the light receiving means by a plurality of rectangular waves, the width of the pulse output by the light receiving means can be detected easily and reliably. Can do.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  1 and 2 show a particle counter according to an embodiment of the present invention. This particle counting apparatus is housed in an exterior body 10 with a particle counting sensor (hereinafter abbreviated as “sensor”) 18 for sampling air and a control board 36 on which a microcomputer 37 serving as a counting means is mounted. Thus, the counted number of particles corresponding to the particle concentration can be displayed on the level display unit 12 as display means.

  The exterior body 10 includes a pair of front and rear cases having a rectangular shape. As shown in FIG. 2, the front case of the exterior body 10 is provided with L-shaped air holes 11 extending from the front to the side at the upper and lower ends of the left side. In addition, on the right side of the front case, a level display unit 12 is provided that displays the counted number of particles in 10 steps using LEDs (not shown). Below the level display unit 12, an alarm display unit 13 indicating an alarm operating state, a reset switch 14 for clearing the counted number of particles, and a set switch 15 for setting an allowable concentration are arranged. It is installed. In addition, the side surface of the front case is provided with a plurality of terminal connection portions 16 such as a connection portion for connecting to a centralized management device such as a well-known personal computer and a connection portion for connecting to a commercial power source. A vent hole 17 is provided. On the other hand, the rear case constituting the exterior body 10 is provided with a known attachment structure for attachment to a wall surface of a clean room or the like.

  As shown in FIG. 1, the sensor 18 includes a sensor main body 19 that introduces indoor air and detects suspended particles, and an output means that converts an analog pulse output from the light receiving means 28 into a digital pulse and outputs the digital pulse. Output circuit 30.

  As shown in FIG. 3, the sensor main body 19 is provided with a heater 25, which is an air introduction means, a light emitting means 26, and a light receiving means 28, inside a light-shielding housing 20.

  The housing 20 includes a flow path 21 in which a lower intake port 21a for taking in air and an upper exhaust port 21b for discharging air are in linear communication, and air introduced by a heater 25 described later. Is caused to flow from the bottom to the top of the housing 20. In the housing 20, a light emitting unit 22 and a light receiving unit 23 are provided symmetrically so as to be positioned at a substantially central portion of the flow path 21. In the present embodiment, the light emitting unit 22 and the light receiving unit 23 are provided at an angle of facing each other at about 60 degrees with respect to the air flow direction in the flow path 21. In other words, the light emitting unit 22 is provided so that the irradiation direction of the light emitting means 26 disposed therein intersects the air flow direction in the flow path 21 at an angle of about 60 degrees in the opposite direction. A light receiving unit 23 is provided so as to be symmetrical to the light emitting unit 22. A position where the centers of the flow path 21, the light emitting part 22, and the light receiving part 23 intersect is the center position of the measurement region R described later. In addition, the air flow guide for restricting the introduced air to the flow path 21 to be equal to or slightly smaller than the size of the measurement region R so as to be located upstream of the measurement region R in the air flow direction. A plate 24 is provided.

  The heater 25 includes a resistance element disposed between the airflow guide plate 24 and the air inlet 21 a in the housing 20. The heater 25 generates heat when energized, so that the vicinity of the intake port 21a in the housing 20 has a negative pressure, thereby sucking indoor air from the intake port 21a and exhausting it from the exhaust port 21b by a chimney effect. It is configured.

  The light emitting means 26 is composed of a semiconductor laser, and is disposed at a closed end of the light emitting portion 22 of the housing 20, and irradiates a central position where the flow path 21, the light emitting portion 22, and the light receiving portion 23 intersect, thereby The particles contained in the gas flowing in the passage 21 are irradiated. A first condenser lens 27 for condensing the emitted light is disposed in front of the light emitting means 26 in the irradiation direction. The first condenser lens 27 outputs the light from the light emitting means 26 as parallel light.

  The light receiving means 28 is composed of a photodiode, and is disposed at a closed end of the light receiving portion 23 of the housing 20, and measures (detects) scattered light from suspended particles due to irradiation of the light emitting means 26, and the received scattered light. The pulse current corresponding to is output. Specifically, the light receiving means 28 is arranged in the direction of the scattering angle of about 60 degrees with respect to the incident optical axis due to the configuration of the housing 20. In other words, the housing 20 is formed so that the light receiving means 28 is arranged in the direction of the scattering angle of about 60 degrees with respect to the incident optical axis. In front of the light receiving direction of the light receiving means 28, a second condensing lens 29 for condensing scattered light from the loose particles is disposed.

  An area where the parallel light output from the light emitting means 27 via the first condenser lens 27 intersects with a range where the light receiving means 28 can collect light via the second condenser lens 29 is in the air. It becomes the measurement area | region R of the suspended particle contained in.

As shown in FIG. 1, the output circuit 30 converts the analog pulse current output from the light receiving means 28 into a digital pulse and outputs the digital pulse. The output circuit 30 includes a current-voltage conversion circuit 31, an amplifier circuit 32, a voltage The comparison circuit 33, a rectangular wave generation circuit 34, and an AND circuit 35 are included.

The current-voltage conversion circuit 31 converts the pulse current output from the light receiving means 28 into a pulse voltage and outputs the pulse voltage.

  The amplifier circuit 32 amplifies and outputs a weak pulse voltage input from the current-voltage conversion circuit 31.

  The voltage comparison circuit 33 outputs a digital pulse voltage when particles larger than a preset particle size to be counted pass. Specifically, in the voltage comparison circuit 33, the peak value (reference voltage value) of the light pulse that reflects the scattering intensity of the suspended particles of the size to be detected is determined in advance by experiments. Then, this reference voltage value is set in the voltage comparison circuit 33, and only when a pulse voltage larger than the reference voltage value is input, High is output, and when a pulse voltage smaller than the reference voltage value is input. , Low is output. As a result, the voltage comparison circuit 33 outputs a digital pulse only when floating particles having a particle size larger than the counting target particle diameter pass through the measurement region R. The reference voltage value is set so that the particle to be counted by the sensor 18 of the present embodiment has a diameter of 0.3 microns or more.

  The rectangular wave generating circuit 34 outputs a rectangular wave of 1 KHz having a pulse width smaller than the pulse width when particles having the smallest particle size to be counted pass at regular intervals.

The AND circuit 35, and outputs a digital pulse input from the voltage comparator circuit 33, the logical product of the digital pulse input from the rectangular wave generating circuit 34.

  The microcomputer 37 is operated by a voltage supplied from a power supply circuit (not shown). In the present embodiment, the microcomputer 37 functions as a counting unit, and turns on a predetermined LED of the level display unit 12 based on the counted number of particles. Display stage. Further, when the reset switch 14 as an input means is operated, the number of particles counted so far is cleared. Further, when the set switch 15 is operated, the permissible concentration corresponding to the number of suspended particles, which is the indoor contamination status, is changed, and the setting status is displayed (lit or flashed) on the level display unit 12. The display on the level display unit 12 is turned off when the setting is completed. Furthermore, the microcomputer 37 is connected to an external output means 38 connected to the terminal connection unit 16.

  Specifically, the microcomputer 37 serving as the counting unit is based on the pulse width input from the light receiving unit 28 via the output circuit 30 and is one or more than the particle size to be counted that has passed through the measurement region R of the sensor 18. The number of particles is counted. In other words, the present embodiment is configured such that counting can be performed even when two or more particles pass through the measurement region R simultaneously by counting based on the input pulse width.

  Next, the output of the pulse corresponding to the scattered light detected by the light receiving means 28 by the output circuit 30 will be specifically described.

First, FIG. 4A shows an analog pulse current output from the light receiving means 28 when one particle having a minimum counting target particle diameter of 0.3 microns passes through the measurement region R, and shows the current voltage. It is an analog pulse voltage after being converted by the conversion circuit 31. This pulse voltage is amplified by the amplifier circuit 32, and then converted into a digital pulse waveform consisting of a rectangular wave of only High or Low by the voltage comparison circuit 33, as shown in FIG. At the same time, as shown in FIG. 4C, a rectangular wave is output from the rectangular wave generating circuit 34 every predetermined time. Then, as shown in FIG. 4D, the logical product circuit 35 outputs a plurality of rectangular waves according to the waveform width of the digital pulse.

FIG. 4E shows an analog pulse current output from the light receiving means 28 when two particles having a minimum counting target particle diameter of 0.3 microns pass through the measurement region R. It is an analog pulse voltage after being converted by the conversion circuit 31. This pulse voltage is amplified in the same manner as described above, and then converted into a digital pulse waveform consisting of a rectangular wave by the voltage comparison circuit 33 as shown in FIG. At the same time, as shown in FIG. 4G, a rectangular wave is output from the rectangular wave generating circuit 34 every predetermined time. Then, as shown in FIG. 4H, the AND circuit 35 outputs a plurality of rectangular waves according to the waveform width of the digital pulse. Here, the pulse in this case has almost no difference in the wave height as shown in FIGS. 4A and 4E, as compared with the case where one particle having the same diameter passes, but FIG. As shown in B) and (F), there is a large difference between the widths W1 and W2.

FIG. 5A shows an analog pulse current output from the light receiving means 28 when one particle having a particle diameter of 0.5 μm, which is the particle size to be counted, passes through the measurement region R. 3 is an analog pulse voltage after conversion by 31. This pulse voltage is amplified in the same manner as described above, and then converted into a digital pulse waveform consisting of a rectangular wave by the voltage comparison circuit 33 as shown in FIG. At the same time, as shown in FIG. 5C, a rectangular wave is output from the rectangular wave generating circuit 34 every predetermined time. Then, as shown in FIG. 5D, the logical product circuit 35 outputs a plurality of rectangular waves according to the waveform width of the digital pulse. Here, the pulse in this case has a large difference in the wave height and a slight difference in the widths W1 and W3 as compared with the case where one 0.3 micron particle passes. The pulse width W3 is smaller than the pulse width W2 when two 0.3 micron particles pass.

FIG. 5 (E) shows an analog pulse current output from the light receiving means 28 when one particle of 1 micron, which is approximately the largest particle diameter to be counted as a suspended particle, passes through the measurement region R, It is an analog pulse voltage after being converted by the current-voltage conversion circuit 31. This pulse voltage is amplified in the same manner as described above, and then converted into a digital pulse waveform composed of a rectangular wave by the voltage comparison circuit 33 as shown in FIG. At the same time, as shown in FIG. 5G, a rectangular wave is output from the rectangular wave generating circuit 34 every predetermined time. Then, as shown in FIG. 5 (H), the logical product circuit 35 outputs a plurality of rectangular waves according to the waveform width of the digital pulse. Here, the pulse in this case has a large difference in the wave height compared with the case where one particle of 0.3 microns and 0.5 microns passes, and there is a slight difference in the widths W1, W3, and W4. Occurs. The pulse width W4 is smaller than the pulse width W2 when two 0.3 micron particles pass.

  That is, the size (diameter) of the particles that have passed through the measurement region R can be determined from the peak value of the pulse output from the light receiving means 28. Therefore, the particle size of the target to be detected can be changed by changing the setting of the reference voltage value in the voltage comparison circuit 33.

Further, the number of particles that have simultaneously passed through the measurement region R can be determined from the pulse width output from the light receiving means 28. That is, the pulse width W2 when two particles having a particle diameter of 0.3 μm that is the counting target particle diameter pass is larger than the pulse width W4 when one particle having a particle diameter of 1 μm that is the counting target particle diameter is passed. Therefore, when a pulse width larger than the pulse width W4 (comparison pulse width) when the 1 micron particle has passed is detected, it is counted that two particles to be counted have passed. In the present embodiment, the output circuit 30 is provided with a rectangular wave generation circuit 34 that outputs a reference rectangular wave and outputs a logical product of the rectangular wave and the detection pulse. By counting the number of pulses of the rectangular wave, the corresponding pulse width can be calculated. A data table indicating the relationship between the number of pulses corresponding to the pulse width and the number of particles corresponding to the number of pulses is stored in advance in a RAM which is a storage unit built in the microcomputer 37.

  Next, the counting control by the particle counter will be specifically described.

  First, when electric power is input by connecting to a commercial power source, the heater 25, the light emitting means 26, and the light receiving means 28 start operation. Further, when the measurement is started after setting the allowable concentration for judging the contamination state by operating the set switch 15, the microcomputer 37 starts counting. This setting operation may be performed by the centralized management apparatus when the particle counting apparatus is connected to the centralized management apparatus via the terminal connection unit 16.

  When the temperature of the heater 25 rises, an ascending airflow is generated due to the chimney effect of the housing 20 of the sensor 18, and indoor air is sucked from the lower intake port 21a. The sucked air is squeezed to pass through the measurement region R by the airflow guide plate 24, passes through the measurement region R, and is exhausted into the room through the exhaust port 21b.

  In the measurement region R, the light emitting means 26 irradiates suspended particles in the air, whereby scattered light is emitted from the suspended particles. When the light receiving means 28 receives the scattered light, the light receiving means 28 outputs an analog pulse current corresponding to the amount of light received. The analog pulse current output from the light receiving means 28 is output as a digital pulse by the output circuit 30 as described above.

  The microcomputer 37 mounted on the control board 36 calculates the corresponding pulse width by counting the number of pulses input from the output circuit 30, and reads the number of particles corresponding to the pulse width from the data table. And displayed on the level display unit 12. When the counted number of particles reaches a set upper limit value, an alarm is output by audio output means mounted on a substrate such as a piezoelectric buzzer.

  As described above, since the sensor 18 applied to the particle counter of the present embodiment outputs the scattered light detected by the light receiving means 28 by a plurality of rectangular waves, the width of the pulse output by the light receiving means 28 can be easily and reliably. Can be detected.

  The particle counter does not count the number of pulses output from the light receiving means 28, but simultaneously counts one or more particles based on the width of the pulses output from the light receiving means 28 via the output circuit 30. Since the configuration is such that counting omissions can be greatly eliminated, highly accurate counting can be performed.

  In addition, the present inventors conducted three types of experiments in order to confirm the accuracy of the configuration and the counting method.

  In the first experiment, a device of the present invention that counts based on pulse width with 0 to 5000 range of 0.3 micron polystyrene latex particles contained in 283 mL of air, and based on the number of pulses. Sensor output (count value) was obtained with a conventional device for counting.

  As a result, in the apparatus of the present invention, as shown in FIG. 6A, the count value increased in proportion to the increase in concentration corresponding to the content, and a linear detection result was shown. On the other hand, in the conventional apparatus, as shown in FIG. 6B, the count value gradually decreased as the concentration increased, indicating a curvilinear detection result. That is, in the conventional apparatus, as the particle concentration increases, the number of particles that simultaneously pass through the measurement region R increases, so that the number of particles that have actually passed through the measurement region R is counted less. In the configuration of the present invention, it can be proved that even if two or more measurement regions R are simultaneously passed, they are hardly affected.

  In the second experiment, the sensor of the present invention and the conventional device were used in a state where the concentration was further increased by containing 0.3 micron polystyrene latex particles in the range of 0 to 20000 in 283 mL of air. Output (count value) was obtained.

  As a result, in the apparatus of the present invention, as shown in FIG. 7A, the counting leakage gradually occurs as the particle concentration increases, but the relationship that the count value increases as the concentration increases is maintained. Yes. On the other hand, in the conventional apparatus, as shown in FIG. 7B, when the particle concentration exceeds 8000 particles, the increase in the count value decreases, and when it exceeds 15,000 particles, the count value decreases. . In other words, even in a high concentration state where the count value decreases in the conventional device, it can be demonstrated that the device of the present invention is less affected by the concentration.

  In the third experiment, in order to determine the influence of the flow rate of the air passing through the flow path 21, 283 mL of air containing 0.3 micron polystyrene latex particles ranging from 0 to 20000 was used. The sensor output (count value) was obtained by supplying air at seven flow rates to the inventive device and the conventional device.

  As a result, in the apparatus of the present invention, as shown in FIG. 8A, even when the air flow rate was changed, the count value at each flow rate was concentrated with almost no change. On the other hand, in the conventional apparatus, the count value also changes according to the change in the flow rate. That is, it can be demonstrated that the apparatus of the present invention is less susceptible to the sampling air flow rate than the conventional apparatus.

  As can be understood from the experimental results, the particle counting device of the present invention can eliminate counting omissions and perform highly accurate counting. Moreover, it is not affected by the air introduction means for sampling the indoor air. As a result, it is not necessary to reduce the measurement region R, and accordingly, an expensive light receiving element or amplifier is not necessary. In other words, according to the configuration of the present invention, it is possible to enlarge the measurement region R compared to the conventional case. In addition, there is no need to use an expensive pump or a flow meter in combination to ensure stable air introduction (sampling). As a result, a highly accurate and inexpensive particle counter can be provided. In other words, in the particle counter of the present embodiment, since it is not affected by the means for introducing air, the air introducing means mounted on the sensor 18 is conventionally used because of its low stability related to introduction. The heating method using the inexpensive heater 25 that has been avoided can be employed.

  In addition, the particle | grain counter of this invention, especially the sensor 18 are not limited to the structure of the said embodiment, A various change is possible.

For example, in the embodiment, the scattering angle of the light receiving unit 23 is set to 60 degrees, but may be between 0 degree and 90 degrees. Further, although the semiconductor laser is used as the light emitting means 26 disposed in the light emitting unit 22, it is not always necessary to use a semiconductor laser, and an LED, a tungsten lamp, or the like may be used. Furthermore, although a photodiode is used as the light receiving means 28 disposed in the light receiving unit 23, it is not necessarily a photodiode, and a phototransistor, a photo IC, or the like may be used. Furthermore, as a method of measuring the waveform width, a logical product with a rectangular wave of 1 KHz is taken, but it is not necessarily 1 KHz, it may be a frequency higher than the frequency of the optical pulse, and preferably 10 times or more. preferable. And if it is the method of measuring a waveform width, it is not necessarily required to take a logical product with a rectangular wave, and the waveform width may be measured directly.

In the above-described embodiment, particles having a particle diameter of 0.3 microns or more are counted by one set of voltage comparison circuit 33, rectangular wave generation circuit 34, and logical product circuit 35. However, a plurality of sets of voltage comparison circuits are used. 33, the rectangular wave generation circuit 34 and the AND circuit 35 are connected in parallel downstream of the amplifier circuit 32, and the reference voltage value in each voltage comparison circuit 33 is changed to thereby change the number of particles having different particle sizes to be counted. You may comprise so that it can detect simultaneously.

It is a block diagram which shows the structure of the particle | grain counter which concerns on embodiment of this invention. The particle counter is shown, (A) is a perspective view, (B) is a cross-sectional view of (A). It is sectional drawing which shows the particle | grain count sensor mounted in an apparatus. (A)-(D) is a drawing showing a pulse when one particle of 0.3 microns passes, (E)-(H) is a pulse when two particles of 0.3 microns pass. It is drawing which shows. (A) to (D) are drawings showing a pulse when one particle of 0.5 microns passes, and (E) to (H) show a pulse when one particle of 1 micron passes. It is a drawing. (A) is a graph which shows the 1st experimental result by the apparatus of this invention, (B) is a graph which shows the 1st experimental result by the conventional apparatus. (A) is a graph which shows the 2nd experimental result by the apparatus of this invention, (B) is a graph which shows the 2nd experimental result by the conventional apparatus. (A) is a graph which shows the 3rd experimental result by the apparatus of this invention, (B) is a graph which shows the 3rd experimental result by the conventional apparatus.

Explanation of symbols

18 ... sensor 21 ... flow path 21a ... intake port 21b ... exhaust port 25 ... heater (air introduction means)
26 ... Light emitting means 28 ... Light receiving means 30 ... Output circuit (output means)
DESCRIPTION OF SYMBOLS 31 ... Current-voltage conversion circuit 32 ... Amplifier circuit 33 ... Voltage comparison circuit 34 ... Rectangular wave generation circuit 35 ... Logical product circuit 37 ... Microcomputer (counting means)
R ... Measurement area

Claims (2)

The introduced air is guided to the measurement region, the light is irradiated to the measurement region by the light emitting means, the scattered light from the particles contained in the air is received by the light receiving means, and the output from the light receiving means is digitally output by the output means. A particle counting sensor that converts and outputs pulses, and
Particle counting apparatus provided with a counting means for counting the number of particles based on the output pulse from the particle count sensor,
The output means of the particle counting sensor is:
A current-voltage conversion circuit that converts the pulse current output from the light receiving means into a pulse voltage and outputs the pulse voltage;
When a pulse voltage larger than a reference voltage value is input from the current-voltage conversion circuit due to the passage of particles larger than a preset particle size to be counted, it becomes High, and when a pulse voltage smaller than the reference voltage value is input, it becomes Low. a comparator circuit for outputting a digital pulse comprising,
A rectangular wave generating circuit that outputs a rectangular wave having a pulse width smaller than the pulse width between high and low of a digital pulse when particles with the smallest particle size to be counted pass;
A logical product circuit that outputs a logical product of the comparison circuit and the rectangular wave generation circuit;
The counting means includes a pulse width calculated by counting the number of rectangular wave pulses input from the AND circuit of the output means , and a comparison pulse width when a particle having a diameter larger than the minimum counting target particle diameter passes. When the output pulse width is equal to or smaller than the comparison pulse width, it is counted that one particle has passed, and when the output pulse width is larger than the comparison pulse width, it is counted that two particles have passed. A particle counter characterized by being configured as described above. 2. The particle counter according to claim 1, wherein the minimum particle diameter to be counted is 0.3 microns, and the particle diameter to be counted as a comparison pulse width is 1 micron.

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