JPS5919302B2 - particle counting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a particle counting device suspended in a fluid medium.

In a conventional particle counting device, for example, as shown in FIG. 1, a particle suspension 2 in which particles are suspended in a fluid medium having a conductivity different from that of the particles in a sample container 1 is formed in a narrow space. When particles pass between the micropores, they are caused to flow through a detector 4 having micropores 3, and are detected by a detection circuit 6 connected to electrodes 5 that are placed close to each other and facing each other across the micropores 3. In a device that detects and counts the change in electrical impedance between the electrodes due to the difference in conductivity between the generated particles and the fluid medium, particles near the micropores, such as particles A and B, are actually found in the micropores. An electric signal is generated not only by passing through the particles C and D, but also by simply passing near the micropores by being caught up in a turbulent flow like particles C and D.

In particular, this phenomenon often occurs in resistance detection type particle detection devices because the detection region thereof extends near the micropores. When the volumes of particles A, B, C, and D are the same, the pulse signals generated by particles C and D are usually smaller than those of particles A and B, and therefore the pulse signals generated by particles C and D are smaller than those of particles A and B. It is possible to distinguish unnecessary pulse signals by passing only the pulse signals, but if the size of the particles is over a wide range, the height of the pulse due to particles A and B and the height of the pulse due to particles C and D can be discriminated. It may happen that the height of the pulses becomes indistinguishable. For example, the particles are red blood cells and blood d-jf
fi, when trying to count a mixture of particles of different sizes at once, if particles A and B are relatively small and particles C and D are relatively large, the generated pulse There is an inconvenience that the heights are almost the same and it is impossible to distinguish between them. For example, JP-A-48-21
In the device described in Publication No. 591, etc., the rise time of a pulse is measured and all pulses with a rise time shorter than a predetermined time are removed to prevent noise signals from being mixed into signal components. However, it has the disadvantage that it requires complex circuits such as a circuit to remove the peak and bottom of the pulse, or a circuit to measure the rise time from the bottom to the peak of the pulse.

The purpose of the present invention is to detect particles by passing a solution in which particles such as blood cells are suspended through micropores and changing the electrical impedance generated at the time, as described above. The present invention provides a particle counting device equipped with a pulse discrimination means to eliminate unnecessary pulse signals other than those caused by the particle counting, and in which two pulses are detected at a voltage level lower than that of the platelet, which is the smallest of the particle signals. A threshold value is set, two comparison circuits are provided corresponding to each threshold value, and the output of the monostable multivibrator is triggered when the particle signal exceeds the lower threshold value, and the output of the monostable multivibrator is triggered when the particle signal exceeds the higher threshold value. By calculating the logical product with the output of the comparison circuit that is turned on, the particle signal that actually passed through the micropore is distinguished from other unnecessary pulse signals.

That is, as shown in the enlarged diagram of the chain line circle in FIG. 1, there are signals emitted when particles A and B pass through the fine hole 3, and signals emitted when particles A and B simply enter the detection area without passing through the fine hole 3. There is clearly a difference in speed between the signals from C and D, and therefore the rise of the particle signals is different.
By using the above-mentioned means, discrimination can be easily performed even with a simple circuit configuration, and the details thereof will be described below.

In this invention, a pulse discrimination circuit is provided between a detection circuit 6 as shown in FIG. 1 and a counting circuit 11 for counting its output signal. As shown in FIG.
and an AND circuit 10 that inputs each of the other comparison circuits 8. FIG. 3 shows an explanatory diagram of its operating principle.

Based on this, 20 in a is the detection circuit 6
The two voltage levels 21 and 22 are set to a level lower than the peak of the pulse signal caused by the smallest particle among the particles to be counted. When the output signal of the detection circuit rises across the lower level, the monostable multivibrator 9 operates as shown at b, and generates a pulse having a pulse width of a predetermined time T. On the other hand, it rises across the higher voltage level 22,
If a comparator circuit is provided that generates an output for a period of time until it crosses again when falling, its output will generate a pulse with a waveform like c. Next, by ANDing b and c, a waveform pulse like d is obtained as the output of the AND circuit. Therefore, among the output signals 20 of the detection circuit 6, since the signals 23 and 24 rise sharply, the output of the AND circuit appears as d, but for the signal 25, the output appears as d. It won't happen.

In other words, the signal waveforms 23 and 24 have high speeds and 2
5 is slow, signals 23 and 24 are signals from particles that actually passed through the micropores, and 25 is a particle that is not to be counted. That is, the output signal of the detection circuit 6 is sent to two comparison circuits 7 and 8, and one of the comparison circuits 7 outputs 1 when the signal is larger than the comparison voltage V1.
(on) and triggers the next monostable multivibrator 9.

The output of the monostable multivibrator 9 remains 1 for a certain period of time T.
(on), and the output is O at other times. On the other hand, the comparison circuit 8 changes from O to 1 (ON) when the signal is larger than the comparison voltage V2, and continues until the signal becomes smaller than 2.

By ANDing the outputs of both monostable multivibrator 9 and comparator circuit 8, if comparator circuit 8 operates during time T, an output will be obtained, but after time T, comparator circuit 8 will output. Even if it works, there is no output.

By counting this output with the counting circuit 11, only pulses based on passage of particles can be counted. The pulse discriminating means described above can provide the same result as differentiating the input signal and determining the magnitude of its slope.

Furthermore, by combining a window comparator, etc., the signal size of platelets passing through the micropores, red blood cells, and white blood cells is significantly different, making it possible to separate platelets from other blood cells. Coincidence counting can be performed without preprocessing.

As described above, the present invention relates to a particle counting device equipped with a discriminating means based on the rising speed of a pulse signal due to the difference in speed between particles that have actually passed through a micropore and particles that have not. It is relatively simple because it is composed of two comparison circuits, a monostable multivibrator, and an AND circuit, and since counting errors are eliminated, highly accurate measurement results can be provided for diagnosis and the like.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional device, FIG. 2 is a block diagram showing the main parts of the present invention, and FIG. 3 is an explanatory diagram showing the principle of operation of the main parts of the present invention. 6...detection circuit, 7,8...comparison circuit, 9...monostable multivibrator, 10...
...AND circuit, 11...Counting circuit.

Claims (1)

[Claims] 1. A sample liquid in which particles are suspended in a fluid medium having a conductivity different from that of the particles, a detector having a fine hole immersed in the sample liquid, and a detector arranged with the fine hole narrowed. a pair of electrodes, a detection circuit that generates a particle detection signal through the electrode when a particle passes through the micropore, and a signal received from the detection circuit and set to a level lower than a minimum amplitude of an output pulse by the particle. Two comparator circuits each having two different comparison voltages; a monostable multivibrator that is triggered by the rising edge of the output of the comparator circuit having a lower comparison voltage to generate a pulse of a predetermined time width; and a comparison circuit having a higher comparison voltage. It is composed of an AND circuit that opens only when the output pulse of the circuit and the output pulse of the multivibrator are output simultaneously, and the output pulse of the detection circuit is caught in turbulence after passing through the pore and crosses the vicinity of the pore. a pulse discrimination circuit that discriminates only particle signals passing through the micropores from signals generated by red blood cells and white blood cells;
A particle counting device comprising a counting circuit that counts output pulses from the discrimination circuit.