JPH0575258B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a device for measuring particles in a fluid, and more particularly to a device for measuring the number density of particles mixed in a fluid using a photon counting method. .

[Prior Art] Conventionally, in such an apparatus, a fluid containing particles in a measurement cell is irradiated with laser light, and the scattered light is used to determine particle characteristics using a photomultiplier tube.

In this case, as the particle size of the particles mixed in the fluid becomes smaller, the scattered light from the particles irradiated with the laser becomes weaker. For weak light detection, rather than using analog photomultiplier tubes,
It is known that photon counting is a more effective method.

First, a conventional device will be explained using FIG. 4.

In FIG. 4, laser light emitted from a laser light source 1 is focused onto a measurement area 3 by a lens 2. In FIG. The measurement region 3 is the inside of the measurement cell 4 through which fluid is flowing. When particles pass into the measurement region, they scatter the incident laser light. The light scattered by the particles is focused by a lens 5 and formed into an image on a slit 6. The light passing through the slit reaches the photocathode of the photomultiplier tube 7. At this time, if light is considered as a particle, that is, a photon, the photon that reaches the photocathode causes electrons to be emitted from the photocathode due to the photoelectric effect. The electrons emitted from the photocathode are amplified by about 10 ⁶ times inside the photomultiplier tube 7, and become an output signal of the photomultiplier tube. This output signal is amplified by a preamplifier 8 and passed through a pulse height discriminator 9. The threshold value of the pulse height discriminator is 1 electron from the photocathode of the photomultiplier tube.
The voltage or current is set to the lower limit that corresponds to the signal when only one of the two is emitted. When the signal amplified by the preamplifier 8 is higher than the threshold of the pulse height discriminator 9, the pulse height discriminator 9 outputs a pulse. The pulse waveform of this pulse is adjusted by the pulse waveform shaping circuit 10 and output as a photoelectronic pulse. The method of counting these photoelectron pulses is the photon counting method. In the photon counting method, the intensity of scattered light from particles corresponds to the number of photoelectron pulses per unit time. Therefore, by counting the number of photoelectron pulses within a certain time interval, the number density of particles in the fluid can be determined from the counted value.

However, as the diameter of the particles mixed in the fluid becomes smaller, the scattered light from the particles irradiated with laser light becomes weaker, and the process of emitting photons from the particles becomes stochastic. Therefore, fluctuations in the count of the number of photoelectron pulses per unit time become large. This fluctuation poses a problem when determining particle characteristics. Arithmetic processing is required to reduce the apparent fluctuation in the count value of this photoelectron pulse and to make it easier to determine the particle characteristics.

A moving average method is effective as this calculation processing method. To explain the moving average method, at a certain time t
Let N(t) be the number of photoelectron pulses counted during a certain time Δt. Hereinafter, this Δt will be referred to as sample time. The number of photoelectron pulses counted between t+Δt and t+2·Δt will be expressed as N(t+1). In this expression, k is an integer: t~t+Δt N(t) t+Δt~t+2・Δt N(t+1) t+2・Δt〜t+3・Δt N(t+2) t+k・Δt〜t+(k+1)・Δt N(t+k) It can be expressed as The moving average processing method is S(t)= _M-1 〓 ^k=0 N(t+k)...(1). Here, M is an adder circuit. By performing such processing, fluctuations in the count value of photoelectron pulses can be reduced in appearance, and particle characteristics can be easily determined.

In the conventional method, as shown in FIG. 4, the photoelectron pulses output from the pulse waveform shaping circuit 10 are counted by the pulse counting circuit 11, the counted value is stored in the memory circuit 12, and the counted value is read and moved by the arithmetic unit. Performs average calculation processing.

[Problems to be Solved by the Invention] In the conventional method as described above, in order to reduce the apparent fluctuation in the count value of photoelectron pulses, the count value of photoelectron pulses is calculated by a calculation device using a moving average method. Processing requires calculation time. That is, it becomes impossible to determine the number density of particles in the fluid in real time.

Therefore, the present invention has been made to solve these problems, and it calculates a moving average in real time to reduce the apparent fluctuation of the count value of photoelectron pulses by the photon counting method. The purpose of the present invention is to provide a particle measuring device that can measure the number density of particles in real time.

[Means for Solving the Problems] In the present invention, in order to solve the above-mentioned problems, moving average processing is performed on the counts of photoelectron pulses obtained from laser scattered light from particles in the fluid. A particle measuring device in a fluid for determining the characteristics of particles, comprising: a laser light source that irradiates a laser beam into a fluid in which particles flow; a means for receiving laser scattered light from the particles and converting it into an electrical signal; and the photoelectric conversion means. (M+1) pulse counting circuits that count the pulses from the pulse generating means and correspond to the number of additions in the moving average process; means for controlling (M+1) pulse counting circuits; a comparator for comparing the count value of the pulse counting circuit with a preset value; and a counting circuit for counting the number of particles from the signal from the comparator. A configuration was adopted in which moving average processing was performed in real time by sequentially operating the (M+1) pulse counting circuits, and particle measurement was performed.

[Operation] In such a configuration, (M+1) is required for pulse counting.
counting circuits are used, and the (M+1)
Since the counting circuits are controlled by (M+1) bit shift registers, the moving average can be processed in real time, and the number density of particles in the fluid can be measured in real time using the photon counting method.

[Example] Hereinafter, an example of the present invention will be described in detail using FIGS. 1 to 3.

FIG. 1 shows the configuration of the apparatus of the present invention, and in FIG. 1, the same parts as in FIG. 4 are given the same reference numerals, and the explanation thereof will be omitted.

The apparatus of the present invention is the same as the apparatus shown in FIG. 4 up to the point where photoelectron pulses are obtained.

Equation (1) representing the above-mentioned moving average corresponds to counting photoelectron pulses for a time period of M·Δt at time t. In other words, if photoelectron pulses are counted in a time period of M·Δt, S at time t
(t) can be found. Furthermore, by using (M+1) counting circuits, the time change of S(t) can be measured.

For this purpose, as shown in Figure 1 (M+1)
pulse counting circuits 21, 22,...2 (M+1)
is provided. Each pulse counting circuit is connected to the pulse waveform shaping circuit 10 via a NAND circuit, and the count output terminal 1 of the shift register 51,
2, . . . performs a counting operation according to the signal from M+1, and outputs the counted value to the latch circuits 31 and 3, respectively.
Latch at 2,...3 (M+1). Selection circuits 41, 42,...4 (M+1) are provided after each latch circuit.
A comparator 55 compares the count values latched in the latch circuit according to the selection signal, and a counter 56 counts the results.

Further, a reference clock generator 54 for generating a reference clock for counting is provided, and the reference clock is inputted to the timer signal generation circuit 52 via a 1/2 frequency divider 53.
The signal from 2 is input to the timer terminal of the shift register 51.

A detailed circuit diagram when the moving average adding circuit M is used twice is shown in FIG. Identical parts in FIG. 1 are given the same numbers. Since the number of additions to obtain the moving average is two, three pulse counting circuits 21 to 23 and a 3-bit shift register 51 are used.
is provided.

The operation of the counting device having such a configuration will be explained with reference to the timing chart shown in FIG.

A photoelectron pulse corresponding to the particle scattered light obtained from the pulse waveform shaping circuit 10 is input to the terminal 72 . The reference clock obtained from the reference clock generator 54 is input to the terminal 71, and the frequency divider circuit 53 divides the clock into 1/2.
Divide the frequency and create clock C2. Here, the reference clock and clock C1 are the same signal. Further, one period of the clock C2 becomes the sample time Δt.
This clock C2 is input to a timer signal generation circuit 52 consisting of a synchronous presettable 4-bit binary counter, and a timer signal TM is output. This timer signal TM is the pulse counting circuit 2.
Determine the counting time of photoelectron pulses 1 to 23.
Now, since the number of additions is set to two, the counting time of photoelectron pulses corresponding to the number of additions is the clock C2.
This is for two cycles. Therefore, the timer signal TM
In this case, two periods of clock C2 are at high level, one period of next clock C2 is at low level, and this operation is repeated. Generally, when adding any number of M times, if the data input to the synchronous presettable 4-bit binary counter 52 is M, the timer signal is at a high level for M periods of the clock C2, and the timer signal is at a high level for M periods of the clock C2. The time of one cycle becomes low level, and this becomes a signal that repeats this operation.

This timer signal TM and clock C2 are input to the shift register 51, and terminals Q0, Q1, Q2
From count T1, count T2, count T3
control signals are generated, and each pulse counting circuit 2
1 to 23 are input. Count T1, count T2, and count T3 are control signals involved in counting photoelectron pulses, and when these control signals are at high level, pulse counting circuits 21 to 23 involved in each control signal count photoelectron pulses. do. When these control signals are low level,
Pulse counting circuit 2 involved in each control signal
1 to 23 do not count photoelectron pulses, and during that time, the corresponding latch circuits 31 to 33 latch the counts of the pulse counting circuits 21 to 23, setting the pulse counting circuits 21 to 23 to the initial state. count 1,
The temporal relationship between count T2 and count T3 is that after count T1 becomes high level, clock C
The count T2 becomes high level after a delay of one period of 2, that is, a time period Δt corresponding to the sample time.
Further, after the count T2 becomes high level, the count T3 becomes high level with a delay of one period of the clock C2. By using such a control method, it is possible to determine the change in S(t) over time.

Count T1, Count T2, Count T3
are inverted by inverters 61 to 63, respectively,
Select S1, select S2, and select S3 are formed. Selects S1, S2, and S3 are control signals for selecting a pulse counting circuit that inputs the count value of photoelectron pulses to the comparator 55. Therefore, these control signals prevent two or more pulse counting circuits from being selected at the same time. When these control signals are at high level, the count value of photoelectron pulses is input to the comparator 55.

Latch L1, latch L2, and latch L3 are control signals for latching the count values counted by pulse counting circuits 21-23 in latch circuits 31-33. The count values of the pulse counting circuit when these control signals are at high level are latched. Latch L
1 is the reference clock, clock C2, and select S1
It becomes high level when all the signals of become high level. Similarly, latch L2 goes high when all signals from reference clock, clock C2, and select S2 go high;
The latch L3 becomes high level when all the signals of the reference clock, clock C2, and select S3 become high level, and the latch circuit 31 becomes high level.
~33 is input.

Further, reset signals R1, R2, and R3 are generated from the clock C2 and the respective counts T1, T2, and T3 to set the pulse counting circuits 21 to 23 for counting photoelectronic pulses to the initial state.
When these signals are at high level, the corresponding pulse counting circuits are set to the initial state. Reset R
1 goes high when clock C2 and count T1 go low at the same time. Similarly,
Reset R2 goes high when clock C2 and count T2 go low at the same time, and reset R3 goes high when clock C2 and count T3 go low at the same time.
becomes high level when both become low level at the same time.

The count values of photoelectron pulses of each of the pulse counting circuits 21 to 23 selected by select S1, select S2, and select S3 are input to the comparator 55. This comparator is set so that a high level signal is output when a count value greater than preset data is input. Even if a count value larger than the preset data is continuously input to the comparator, the output signal from the comparator 55 remains at a high level. When a count value smaller than the preset data is input to the comparator, the output signal from the comparator becomes low level. When the output signal from the comparator changes from high level to low level, the counter 56
counts. Here, the data preset in the comparator 55 corresponds to the particle diameter of particles in the fluid, and the count value displayed on the display 65 is a value related to the number density of particles in the fluid.

In addition, by employing multiple sets of comparators,
It is also possible to measure the number density of multiple particle sizes.

Furthermore, in the embodiment, the number of additions of the moving average is set to 2.
Although the number of additions has been described as 1 times, it goes without saying that this number of additions can be extended to any number of M times.

[Effects of the Invention] As explained above, according to the present invention, pulse counting corresponds to the number of additions of moving average processing (M+
1) Moving average processing is performed by sequentially operating pulse counting circuits, which reduces the apparent fluctuation of the photoelectron pulse count and makes it easier to determine particle characteristics in the fluid. The average can be processed in real time, and the number density of particles can be measured in real time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the device of the present invention;
FIG. 2 is a detailed circuit diagram of a portion that counts photoelectron pulses, FIG. 3 is a timing chart explaining the operation, and FIG. 4 is a block diagram showing a conventional configuration. 21-23...Pulse counting circuit, 31-33...
...Latch circuit, 41-43...Selection circuit, 55...
...Comparator, 56...Counter.

Claims (1)

[Scope of Claims] 1. A particle measuring device in a fluid that calculates particle characteristics by performing moving average processing on the count values of photoelectron pulses obtained from laser scattered light from particles in the fluid, comprising: a fluid in which particles flow; a laser light source that irradiates a laser beam into the interior of the particle; a means for receiving laser scattered light from particles and converting it into an electrical signal; and a pulse generator that converts the signal from the photoelectric conversion means into a number of pulses corresponding to the intensity of the scattered light. (M+1) pulse counting circuits that count the pulses from the pulse generating means and correspond to the number of additions M in the moving average process; means for controlling the (M+1) pulse counting circuits; A comparator that compares the count value of the counting circuit with a preset setting value, and a counting circuit that counts the number of particles from the signal from the comparator, and sequentially operates the (M+1) pulse counting circuits. A particle measuring device in a fluid is characterized in that it measures particles by performing moving average processing in real time. 2. The means for controlling the pulse counting circuit is (M+
1) The particle measuring device in a fluid according to claim 1, which is a bit shift register.