A particle counter and its signal processing circuit

Abstract

This application discloses a particle counter and its signal processing circuit, relating to the field of particle counting. It is used to detect and count the scattered light from particles. To address the problem that current particle amplification methods cannot achieve good amplification for particles of different sizes, a signal processing circuit is provided. This circuit includes a multi-layered signal processing unit, each layer consisting of one or more signal amplification circuits connected in series. By setting the specific amplification factor of each signal amplification circuit, and through the multi-layered series structure, any number of signals with different amplification factors can be amplified in various combinations. This allows for specialized amplification and counting of particles with different size ranges, simultaneously accommodating particles of varying sizes. It ensures that large particles are amplified without distortion while maintaining the signal recognition rate for small particles, effectively improving the accuracy of the particle counter.

Description

Technical Field

[0001] This application relates to the field of particle counting, and in particular to a particle counter and a signal processing circuit for the particle counter. Background Technology

[0002] A particle counter monitors the scattered light from particles, converting the scattered light signal into photocurrent, which is then further converted into voltage pulse signals. These voltage pulse signals are then categorized by particle size. The signals are amplified, filtered, and denoised multiple times to obtain the particle signal, which is then identified and counted according to the defined particle size. A particle counter typically has multiple particle size standards; each standard's counter counts particles larger than its designated size.

[0003] The number of particles monitored in an environmental particle monitoring operation is in the tens of thousands. The particle size of each particle is continuously distributed within the particle size range. In contrast, in Mie scattering, the particle size and signal intensity increase cubically with increasing particle size. Particle counters used for clean space measurements typically measure particle sizes ranging from 0.1 μm to tens of micrometers. To identify small-diameter particles, high-magnification amplification is unavoidable. Existing technologies amplify the output signal of the I / V conversion circuit within the same amplifier circuit and then directly compare and count it with the corresponding comparator circuits for each particle size standard. Alternatively, the output signal of the I / V conversion circuit is amplified within the same amplifier circuit and then amplified again as needed. However, due to the differences in particle size among the particles to be detected, the resulting particle signals have magnitude differences. When small-particle and large-particle signals pass through the same operational amplifier circuit for signal amplification, the output particle signal is actually greater than the maximum operating voltage of the given operational amplifier circuit, resulting in distortion. While considering the identification of small-particle signals, this inevitably leads to distortion of the large-particle signal output or a significant increase in the maximum voltage of the operational amplifier circuit. However, significantly increasing the maximum operating voltage of the operational amplifier inevitably introduces circuit noise and increases the random noise of amplified stray light during particle detection. On the other hand, limiting the operating voltage while ensuring that the large-particle signal is amplified without distortion will greatly reduce the recognition rate of small-particle signals.

[0004] Therefore, it is evident that how to enable a particle counter to identify particles of various sizes while maintaining high accuracy is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this application is to provide a particle counter and a signal processing circuit for the particle counter, which enables the particle counter to identify particles of various sizes while maintaining the accuracy of the identification.

[0006] To solve the above-mentioned technical problems, this application provides a signal processing circuit for a particle counter, comprising:

[0007] The I / V conversion circuit is used to convert the current signal of the particles output by the photodetector in the particle counter into a voltage pulse signal; the signal processing unit is used to amplify and reduce the noise of the received voltage pulse signal; the comparison and counting unit is used to count the amplified and noise-reduced voltage pulse signal; wherein, the input terminal of the signal processing unit is connected to the I / V conversion circuit, and the output terminal is connected to each comparison and counting unit in a corresponding manner.

[0008] The signal processing unit includes N layers of processing circuits connected in series, where N≥2. Each layer of processing circuits includes one or more signal amplification circuits, and the amplification factor of each signal amplification circuit is different.

[0009] The input terminal of the first-level processing circuit is connected to the I / V conversion circuit as the input terminal of the signal processing unit. Each signal amplification circuit of any processing circuit is connected to one of the signal amplification circuits of the processing circuit above it. The output terminal of any signal amplification circuit in any processing circuit that is not connected to the next processing circuit is connected to the comparison counting unit as the output terminal of the signal processing unit.

[0010] The comparison counting unit is connected to each output terminal of the signal processing unit in a one-to-one correspondence. It is used to compare the voltage pulse signal output by the signal processing unit with a preset comparison threshold and count the voltage pulse signal according to the comparison result. The comparison threshold is determined according to the corresponding preset particle size standard and the amplification factor of each signal amplification circuit corresponding to the output terminal to which the comparison counting unit is connected.

[0011] Preferably, the comparison counting unit is connected to the processor, which is used to analyze and process the counting results of the comparison counting unit.

[0012] Preferably, among the comparison thresholds corresponding to each comparison counting unit, at least two comparison thresholds are determined based on the same preset particle size standard, and respectively correspond to different signal amplification circuits in the first layer processing circuit, which are used to provide counting results for the processor to perform mutual checks and determine whether the signal processing unit is abnormal.

[0013] Preferably, each signal amplification circuit includes one or more of an inverting amplifier circuit, a non-inverting amplifier circuit, and a follower circuit.

[0014] Preferably, one or more coupling capacitors are provided between the I / V conversion circuit, the processing circuit, and the signal processing unit, which are connected in series.

[0015] Preferably, one or more grounded high-pass filter capacitors are provided between the I / V conversion circuit, the processing circuit, and the signal processing unit, which are connected in series.

[0016] Preferably, one or more voltage divider resistors are provided between the I / V conversion circuit, the processing circuit, and the signal processing unit, which are connected in series.

[0017] Preferably, it also includes an early warning unit connected to the processor. When the processor's mutual inspection result indicates that the signal processing unit is abnormal, the early warning unit is controlled by the processor to issue an alarm.

[0018] To address the aforementioned technical problems, this application also provides a particle counter, including the signal processing circuit of the aforementioned particle counter.

[0019] The signal processing circuit for the particle counter provided in this application includes a multi-layered signal processing unit. Each layer consists of one or more signal amplification circuits, and the layers are connected in series. Thus, by setting the specific amplification factor of each signal amplification circuit, any number of signals with different amplification factors can be amplified in various combinations through the multi-layered series structure. When the scattered light emitted by the particle counter is converted into a pulse signal by the I / V conversion circuit, it passes through the signal processing unit and, through different paths, obtains signals with different amplification factors. The signal then enters a comparison counting unit connected to the signal processing unit. The number of comparison counting units is the same as the number of output terminals of the signal processing unit, that is, the number of signal amplification paths. This means that the pulse signals amplified by different amplification factors are counted by different comparison counting units, and the preset comparison thresholds of the different comparison counting units are also different, achieving an adaptive particle counting effect for pulse signals amplified by different amplification factors. With the above structure, even if the number of particles detected in a single particle environment is in the tens of thousands, particles of different sizes can be amplified at different magnifications and counted accordingly. This takes into account particles of different sizes, ensuring that large particles are amplified without distortion and that the recognition rate of small particle signals is guaranteed, which is beneficial to improving the accuracy of the particle counter.

[0020] Furthermore, the particle counter provided in this application has the same beneficial effects as the signal processing circuit of the aforementioned particle counter. Attached Figure Description

[0021] To more clearly illustrate the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1This application provides a schematic diagram of the signal processing circuit of a particle counter.

[0023] Figure 2 This is a structural diagram of a signal processing circuit example for a particle counter provided in this application. Detailed Implementation

[0024] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this application.

[0025] The core of this application is to provide a particle counter and a signal processing circuit for the particle counter, which enables the particle counter to identify particles of various sizes while ensuring the accuracy of the identification.

[0026] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] When a particle counter performs a single particle count, the number of particles counted is usually in the tens of thousands, and the particle size is not uniform. The particle size of each particle is continuously distributed within the particle size range. In Mie scattering, the particle size and signal intensity increase with the particle size by a cubic order. The particle size standard for particle counters used for clean space measurements is usually from 0.1 μm to tens of micrometers.

[0028] Large-diameter particles are relatively easy to identify, and the counting accuracy is relatively guaranteed. However, small-diameter particles require high magnification to be effectively identified; otherwise, the counting accuracy of the particle counter will be greatly affected.

[0029] Currently, a signal amplification circuit is typically used to amplify small particles. However, this method also amplifies large particles by the same factor, potentially causing large particles to exceed the maximum operating voltage of the operational amplifier circuit, thus resulting in distortion. Furthermore, the particle size of small particles can vary by orders of magnitude. What is a suitable amplification factor for some small particles may be too small for others to be accurately identified by a particle counter.

[0030] In summary, to solve the above problems, such as Figure 1 As shown, this application provides a signal processing circuit for a particle counter, comprising:

[0031] I / V conversion circuit 101 is used to convert the current signal of the particles output by photodetector 102 in particle counter into voltage pulse signal; signal processing unit 103 is used to amplify and reduce noise of the received voltage pulse signal; comparison counting unit 104 is used to count the amplified and noise-reduced voltage pulse signal; wherein, the input terminal of signal processing unit 103 is connected to I / V conversion circuit 101, and the output terminal is connected to each comparison counting unit 104 in a corresponding manner;

[0032] The signal processing unit 103 includes N layers of processing circuits connected in series, where N≥2. Each layer of processing circuit includes one or more signal amplification circuits, and the amplification factor of each signal amplification circuit is different.

[0033] The input terminal of the first-level processing circuit is connected to the I / V conversion circuit 101 as the input terminal of the signal processing unit 103. Each signal amplification circuit of any layer processing circuit is connected to one of the signal amplification circuits of the layer above it. The output terminal of any signal amplification circuit in any layer processing circuit that is not connected to the next layer processing circuit is connected to the comparison counting unit 104 as the output terminal of the signal processing unit 103.

[0034] The comparison counting unit 104 is connected to each output terminal of the signal processing unit 103 in a one-to-one correspondence. It is used to compare the voltage pulse signal output by the signal processing unit 103 with a preset comparison threshold and count the voltage pulse signal according to the comparison result. The comparison threshold is determined according to the corresponding preset particle size standard and the amplification factor of each signal amplification circuit corresponding to the output terminal to which the comparison counting unit is connected.

[0035] The path from a signal amplifier circuit in the first-level processing circuit to an output terminal to output the amplified and noise-reduced voltage pulse signal is the amplification path corresponding to that output terminal.

[0036] Multiple comparison counting units 104 are connected to the output of the signal processing unit 103. Each comparison counting unit 104 has a corresponding comparison threshold for counting the voltage pulse signal of a particle that meets a preset particle size standard. Since the voltage pulse signals formed by particles of various sizes are processed by the signal processing unit 103 before entering the comparison counting units, the comparison threshold is determined based on the corresponding preset particle size standard and the amplification factor of the signal amplification circuit in the signal processing unit that forms the signal path to which the comparison counting unit is connected. The comparison thresholds of each comparison counting unit 104 are not identical. While the comparison thresholds in each comparison counting unit are similar, considering the noise impact caused by the complexity of the circuit in practical applications, the comparison thresholds of the units used for comparison in each unit are set to be similar or the same, without any order-of-magnitude difference. The counting principle of the comparison counting unit is that each unit counts the voltage pulse signal received at its corresponding output terminal when the signal exceeds its corresponding comparison threshold. Therefore, the comparison threshold can be determined by combining a preset particle size standard and the amplification factor of the signal amplification circuit in the signal processing unit connected to the comparison counting unit, which forms the signal path. This allows the comparison counting unit to count particles larger than or equal to the preset particle size standard. Each comparison counting unit typically includes a comparison unit and a counting unit. The comparison unit can be a comparator circuit, and the counting unit can be a counting circuit or implemented through a counter program. Based on existing technology, the selection of the comparison counting unit is not specifically limited here.

[0037] like Figure 2 As shown, the I / V conversion circuit 101 converts the particle current signal output from the photodetector 102 in the particle counter into a voltage pulse signal, and then outputs it to the first-layer processing circuit of the signal processing unit 103. Specifically, in Figure 2 In one possible implementation shown, the first-layer processing circuit includes two signal amplification circuits; that is, in the first-layer processing circuit, the particle travels through two amplification paths. Here, the photodetector is typically selected from photodiodes, photomultiplier tubes, etc.

[0038] And from Figure 2 It can be seen that the first-layer processing circuit contains two signal amplification circuits 1A and 1B. Signal amplification circuit 1A is not connected to the next layer processing circuit (i.e., the second layer processing circuit), but is directly connected to a comparison counting unit 104. That is, it serves as an output terminal (temporarily referred to as output terminal 1) of the signal processing unit 103 to output the amplified particle pulse signal. The amplification path is signal amplification circuit 1A. Correspondingly, the amplification factor of output terminal 1 is also the amplification factor of signal amplification circuit 1A.

[0039] The second-layer processing circuit includes three signal amplification circuits 2A, 2B, 2C, and 2D. 2A is connected to signal amplification circuit 1A in the first-layer processing circuit to form the amplification path corresponding to output terminal 2. 2B, 2C, and 2D are connected to signal amplification circuit 1B in the first-layer processing circuit to form the amplification paths corresponding to output terminals 2, 3, and 4, respectively. Signal amplification circuits 2A, 2B, and 2C are not connected to the next layer processing circuit (i.e., the third-layer processing circuit). Instead, they serve as the other three output terminals 2, 3, and 4 of signal processing unit 103, connected to the corresponding comparison and counting units 104 (i.e., comparison and counting units 2, 3, and 4). That is:

[0040] The amplification path corresponding to output terminal 2 is signal amplifier circuit 1A - signal amplifier circuit 2A, and its amplification factor is the amplification factor of signal amplifier circuit 1A * the amplification factor of signal amplifier circuit 2A; the same applies to output terminal 3, and its amplification factor is the amplification factor of signal amplifier circuit 1B * the amplification factor of signal amplifier circuit 2B; the amplification factor of output terminal 4 is the amplification factor of signal amplifier circuit 1B * the amplification factor of signal amplifier circuit 2C.

[0041] Since the amplification factors of each signal amplifier circuit are not exactly the same, that is, the amplification factors of each signal amplifier circuit can be different or the same, but the final amplification factor of the output terminals such as output terminals 1, 2, 3, and 4 depends on the amplification factor of the corresponding amplification path of each output terminal. For example, after the I / V conversion circuit 101 outputs a voltage pulse signal, the signal amplifier circuits 2B and 2C with different amplification factors, output terminals 3 and 4 can obtain two particle signal outputs with different amplification factors.

[0042] Furthermore, the third-layer processing circuit also includes signal amplification circuits 3A and 3B. The principle of the amplification factor corresponding to the output terminals 5 and 6 is the same as that described above, and will not be repeated here in this embodiment.

[0043] When the preset particle size standard on which the comparison threshold of each comparison counting unit is based is different, the amplification factor of the amplification path corresponding to each output terminal of the signal processing unit 103 connected to each comparison counting unit 104 is different.

[0044] Furthermore, the signal amplification circuits in the first-layer processing circuit have different amplification factors. When a multi-channel signal amplification circuit in the Nth-layer processing circuit is connected to the same amplification circuit output terminal in its upper-layer processing circuit, the amplification factors of the multi-channel signal amplification circuit in the Nth-layer processing circuit are different. When a multi-channel signal amplification circuit in the Nth-layer processing circuit is connected to different amplification circuit output terminals in its upper-layer processing circuit, the amplification factors of the multi-channel signal amplification circuit in the Nth-layer processing circuit can be the same or different. Even further, the amplification factors of the signal amplification circuits in different layers of processing circuits can be the same or different.

[0045] exist Figure 2 In one possible implementation, for output terminals 3 and 4, the amplification factors of output terminals 3 and 4 need to be different to achieve this. However, for output terminals 3-4 to have different output factors from output terminals 1 and 2, the above strict restriction is not required. The amplification factor of signal amplifier circuit 1A does not need to be equal to the amplification factor of signal amplifier circuit 1A multiplied by the amplification factor of signal amplifier circuit 2A, or the amplification factor of signal amplifier circuit 1B multiplied by the amplification factor of signal amplifier circuit 2B, or the amplification factor of signal amplifier circuit 1B multiplied by the amplification factor of signal amplifier circuit 2C. The amplification factor of signal amplifier circuit 1A can be arbitrarily equal to any of the signal amplifier circuits in other processing layers, such as 2A, 2B, and 2C (note that 2B and 2C cannot be equal). The amplification factor of signal amplifier circuit 2A can be equal to any one of 2B and 2C. This is the meaning that the amplification factors of the signal amplifier circuits are not exactly the same, but rather completely different.

[0046] Furthermore, in specific implementations, the I / V conversion circuit 101 often employs a transimpedance amplifier, which will not be specifically described in this embodiment. In addition to amplifying the signal, the signal amplification circuit typically also reduces noise, achieved through a specific circuit structure. Since there are already various circuit structures for noise reduction, they will not be elaborated upon in this embodiment.

[0047] It is readily understood that the signal processing unit 103 provided in this application includes multiple output terminals, and the amplification factor corresponding to each output terminal is not entirely the same. Therefore, the preset particle size standard for counting particles is not entirely the same. Typically, the amplification factor of the amplification path corresponding to the output terminal of the signal processing unit 103 for different preset particle size standards is different. The amplification factor of the output terminal of the signal processing unit 103 for the same preset particle size standard can be the same or different. Accordingly, each comparison counting unit 104 that subsequently counts the particle pulse signal output from the output terminal of the signal processing unit 103 counts based on the comparison result after comparing the output terminal signal with the comparison threshold of the corresponding comparison counting unit. It is readily known that the preset comparison threshold of each comparison counting unit 104 should be related to the particle size of the particle it targets, i.e., the preset particle size standard, and the amplification factor of the amplification path corresponding to the connected output terminal.

[0048] It should be noted that the reason why the output terminals with different amplification ratios are not completely targeted at the same particle size is that, from the perspective of amplification, different amplification ratios should correspond to different particle sizes to facilitate the effective identification of signals formed by particles of different sizes.

[0049] The preferred method described above is as follows: the comparison counting unit 104 is connected to the processor, and the processor is used to analyze and process the counting results of the comparison counting unit 104, such as calculating the number and concentration of particles in each particle size standard range, and calculating the concentration of standard particles in each particle size.

[0050] Furthermore, among the comparison counting units 104 connected to the processor, at least two comparison thresholds are determined based on the same preset particle size standard and correspond to different signal amplification circuits in the first-layer processing circuit, which are used to provide counting results for the processor to perform mutual checks and determine whether the signal processing unit 103 is abnormal.

[0051] It is readily apparent that since at least two comparison thresholds are determined based on the same preset particle size standard, corresponding to two different output terminals of the signal processing unit and different signal amplification circuits in the first-layer processing circuit, but used for counting particles that meet the same preset particle size standard after amplification, at least two comparison counting units 104 count particles that meet the same preset particle size standard. When the preset particle size standard on which the comparison thresholds of multiple comparison counting units are based is the same, the amplification factor of the amplification path corresponding to each output terminal of the signal processing unit 103 connected to these multiple comparison counting units 104 can be the same or different. Because the amplification factor is included in the influence factor when the comparison threshold is set, for the same preset particle size standard, the counting results of the two comparison counting units 104 should be consistent within the error range to indicate that the particle counter is working normally. If they are inconsistent, it indicates that there is a problem. This completes the self-check of the particle counter counting results, thereby further ensuring the counting accuracy.

[0052] However, it should be noted that this embodiment does not impose further restrictions on the processor described above. It only needs to be a hardware device capable of data processing, such as a central processing unit (CPU), digital signal processor (DSP), field-programmable gate array (FPGA), programmable logic array (PLA), microcontroller, etc. Those skilled in the art can choose a suitable hardware device to implement the steps performed by the processor described above.

[0053] Furthermore, for the preferred cross-checking scheme provided above, the self-checking results can be determined using an error threshold. This avoids unnecessary maintenance costs arising from minor differences in counting results due to noise or other interference in the circuit. However, it should be noted that the error threshold should not be too large and can be set based on experience. For example, if the counting results of two particles meeting the same particle size standard are both close to 1000, the error threshold can be set to 10. In this case, if the difference between the two counting results is greater than 10, the counting result is considered abnormal.

[0054] The signal processing circuit of the particle counter provided in this application includes an I / V conversion circuit 101, a signal processing unit 103, and multiple comparison counting units 104. The I / V conversion circuit 101 is connected to a photodetector 102 and is used to convert the current signal output by the photodetector 102 into a voltage pulse signal. The signal processing unit 103 includes multiple processing circuits connected in series. Each processing circuit includes one or more signal amplification circuits. The amplification factor of each signal amplification circuit is different. By arranging and combining the signal amplification circuits, multiple paths for amplifying the voltage pulse signal at different factors can be formed and output from the corresponding output terminal to the corresponding comparison counting unit 104. Each comparison counting unit 104 has a built-in comparison threshold determined according to a preset particle size standard and the corresponding amplification factor to realize particle counting. As can be seen, the circuit achieves differentiated amplification of the voltage pulse signal converted by the photodetector 102 through the signal processing unit 103, and then uses the comparison counting units 104 with different comparison thresholds to identify and count particles of various sizes. This enables accurate particle counting of pulse signals containing particles of different sizes, thus improving the counting accuracy of the particle counter.

[0055] Based on the above embodiments, this embodiment provides a preferred implementation to further illustrate the structure of the signal amplification circuit: the signal amplification circuit includes one or more of an inverting amplifier circuit, a non-inverting amplifier circuit, and a follower circuit.

[0056] The inverting amplifier circuit consists of an inverting amplifier, and the non-inverting amplifier circuit consists of a non-inverting amplifier. In specific implementations, since the voltage pulse signal converted by the I / V conversion circuit 101 is in the opposite direction to the preset voltage signal, the inverting amplifier circuit is needed to perform phase correction and amplification of the voltage pulse signal. To further amplify the voltage pulse signal, it can be amplified again by the non-inverting amplifier circuit.

[0057] It should be noted that there can be one in-phase amplifier circuit, used only for amplification, or there can be multiple circuits, which, in addition to amplification, also function as voltage followers. This embodiment does not limit the number of in-phase amplifier circuits.

[0058] It is understood that another possible implementation of the signal amplification circuit also includes multiple voltage divider resistors. One or more voltage divider resistors are provided between the I / V conversion circuit 101, the processing circuits of each layer, and the comparison counting unit 104 connected in series, for the purpose of protecting the circuit.

[0059] This embodiment provides a preferred solution to supplement the description of the structure of the signal amplification circuit. In this embodiment, the signal amplification circuit includes one or more of an inverting amplifier circuit, a non-inverting amplifier circuit, and a follower circuit. The voltage pulse signal converted by the I / V conversion circuit 101 is phase-corrected by the inverting amplifier circuit, and then amplified again by the non-inverting amplifier circuit. By amplifying the voltage pulse signal, small-diameter particles can be identified, thereby further improving the counting accuracy of the particle counter.

[0060] Based on the above embodiments, since stray light in the particle counter is converted into a voltage signal by the photodetector 102, and the circuit also generates noise, affecting the counting results of the particle counter, this embodiment also provides a preferred implementation scheme to reduce noise and improve the counting accuracy of the particle counter.

[0061] One or more coupling capacitors are provided between the I / V conversion circuit 101, the processing circuit, and the signal processing unit 103, which are connected in series.

[0062] The aforementioned coupling capacitors are mainly used to achieve low-frequency filtering between circuits, thereby achieving a better noise reduction effect in the low-frequency range of pulse signals.

[0063] Similarly, this embodiment also provides another preferred implementation:

[0064] One or more grounded high-pass filter capacitors and resistors are provided between the I / V conversion circuit 101, each layer of processing circuits and the comparison counting unit 104, which are connected in series, to form an RC filter.

[0065] The high-pass filter capacitor added in this embodiment to the circuit structure of the above embodiment is used to implement high-pass filtering, thereby achieving a better noise reduction effect on the high-frequency band of the pulse signal.

[0066] Based on the two preferred embodiments described above, noise reduction in the low-frequency band and noise reduction in the high-frequency band can be implemented in the signal processing circuit of the particle counter provided in this application, so as to maximize the noise reduction effect and minimize the noise interference contained in the pulse signal used for particle counting, thereby improving the counting accuracy of the particle counter.

[0067] As can be seen from the above embodiments, by setting at least two comparison counting units 104 and processors with the same particle size standard for corresponding particles, mutual inspection of counting results can be achieved, and further, self-inspection results can be determined in the form of error threshold.

[0068] Therefore, after determining the self-test result, this embodiment also provides a preferred implementation scheme. The signal processing circuit of the particle counter mentioned above also includes an early warning unit connected to the processor, which is used to issue an alarm under the control of the processor when the processor determines that the mutual test result is abnormal in the signal processing unit 103.

[0069] The warning unit can be a buzzer, which emits an audible signal to issue an alarm; it can also be an indicator light, which emits a light signal to issue an alarm; or it can be a wireless communication module, which establishes a communication connection with the user's mobile terminal and issues warnings via push notifications, emails, messages, etc. This embodiment does not limit the type of warning unit or the warning method.

[0070] It should be noted that the signal processing circuit of the particle counter may also include a display connected to the processor, used to display the comparison counting unit information of the counting anomaly and its corresponding output terminal. In specific implementation, when the processor determines that there is an anomaly in the cross-check counting result, it will send a control signal to the early warning unit to control the early warning unit to issue an early warning, and display the comparison counting unit information and its corresponding output terminal on the display to indicate the location of the abnormal circuit to the user, saving the user time in locating the abnormal device.

[0071] The preferred solution provided in this embodiment sets up an early warning unit connected to the processor to issue an alarm when the processor determines that the counting result of the cross-check is abnormal, so as to notify the user that the particle counter is counting abnormal and that there is a fault in the signal processing circuit of the particle counter, thereby enabling maintenance personnel to quickly troubleshoot and repair the fault and restore the normal operation of the particle counter.

[0072] Finally, this application embodiment also provides a particle counter, which, in addition to the photodetector 102, also includes the signal processing circuit of the particle counter mentioned in the above embodiments. Since the components have been described in detail above, they will not be repeated in this embodiment.

[0073] The particle counter provided in this application includes the signal processing circuit of the aforementioned particle counter. This signal processing circuit includes an I / V conversion circuit 101, a signal processing unit 103, and multiple comparison and counting units 104. Through the special hierarchical structure of the signal processing unit 103 and the setting of the amplification factor of the signal amplification circuit in each layer of the processing circuit, the signal processing unit 103 can specifically amplify the voltage pulse signal output by the I / V conversion circuit 101. Each output port is connected to a comparison and counting unit 104 with a built-in preset comparison threshold, thereby performing differentiated particle counting technology to ensure better counting results for particle sizes of different orders of magnitude. Therefore, the particle counter provided in this application can perform differentiated amplification and differentiated counting of voltage pulse signals containing particles of different sizes, thereby providing maximum accuracy in the counting results and better meeting the needs of actual production and daily life.

[0074] The particle counter and its signal processing circuit provided in this application have been described in detail above. The various embodiments in the specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section. It should be noted that those skilled in the art can make several improvements and modifications to this application without departing from the principles of this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

[0075] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

Claims

1. A signal processing circuit for a particle counter, characterized in that, include: The I / V conversion circuit is used to convert the current signal of the particles output by the photodetector in the particle counter into a voltage pulse signal. The signal processing unit is used to amplify and reduce noise in the received voltage pulse signal; the comparison counting unit is used to count the amplified and noise-reduced voltage pulse signal; wherein, the input terminal of the signal processing unit is connected to the I / V conversion circuit, and the output terminal is connected to each comparison counting unit in a corresponding manner. The signal processing unit includes N layers of processing circuits connected in series, where N≥2. Each layer of processing circuits includes one or more signal amplification circuits, and the amplification factor of each signal amplification circuit is not the same. Each signal amplification circuit includes one or more of the following: inverting amplifier circuit, non-inverting amplifier circuit, and follower circuit. The input terminal of the first-layer processing circuit is connected to the I / V conversion circuit as the input terminal of the signal processing unit. Each signal amplification circuit of any layer of processing circuit is connected to one of the signal amplification circuits of the processing circuit above it. The output terminal of any signal amplification circuit in any layer of processing circuit that is not connected to the next layer of processing circuit is connected to the comparison counting unit as the output terminal of the signal processing unit. The comparison counting unit is connected to each output terminal of the signal processing unit in a one-to-one correspondence, and is used to compare the voltage pulse signal output by the signal processing unit with a preset comparison threshold, and count the voltage pulse signal according to the comparison result; The comparison counting unit is connected to the processor, and the processor is used to analyze and process the counting results of the comparison counting unit. The comparison threshold is determined based on the corresponding preset particle size standard and the amplification factor of each signal amplification circuit corresponding to the output terminal connected to the comparison counting unit. Among the comparison thresholds corresponding to each comparison counting unit, at least two comparison thresholds are determined based on the same preset particle size standard and correspond to different signal amplification circuits in the first layer of the processing circuit, which are used to provide counting results for the processor to perform mutual checks and determine whether the signal processing unit is abnormal.

2. The signal processing circuit of the particle counter according to claim 1, characterized in that, One or more coupling capacitors are provided between the I / V conversion circuit, the processing circuits in each layer, and the comparison counting unit, which are connected in series.

3. The signal processing circuit of the particle counter according to claim 1, characterized in that, One or more grounded high-pass filter capacitors are provided between the I / V conversion circuit, the processing circuits in each layer, and the comparison counting unit, which are connected in series.

4. The signal processing circuit of the particle counter according to claim 1, characterized in that, One or more voltage divider resistors are provided between the I / V conversion circuit, the processing circuits in each layer, and the comparison counting unit, which are connected in series.

5. The signal processing circuit of the particle counter according to claim 1, characterized in that, It also includes an early warning unit connected to the processor. When the processor's mutual inspection result indicates that the signal processing unit is abnormal, the early warning unit is controlled by the processor to issue an alarm.

6. A particle counter, characterized in that, The signal processing circuit of the particle counter as described in any one of claims 1 to 5.

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