JPS6129461B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for counting particles such as blood cells and platelets.

Conventionally, devices for counting such particles, such as platelets, pass a suspension in which platelets, blood cells, etc. are suspended, through micropores, and the micropores are counted based on the difference in electrical impedance between the particles and the suspension. A detection signal is obtained in which a pulse signal 1 as shown in Fig. 1 is generated every time a particle passes, and the magnitude of these pulse signals is within thresholds V1 and V2 corresponding to the upper and lower limits of platelets. There was a device that distinguished platelets from platelets and counted their number. However, if the baseline 2 rises as shown in the figure due to particles that have already passed through the micropore passing near the micropore or due to external noise, etc., and pushes the pulse signal 1 above the threshold value V1, In reality, there was a problem in that the pulse signal 1 corresponding to platelets was not counted. Therefore, it is possible to pass the detection signal through a differentiating circuit, but if the time constant is made small, the fluctuation of baseline 2 will be removed, but pulse signal 1 will also be modified, and the signal with a larger rise than the signal with a large magnitude will be This produced a larger output signal and was more likely to cause counting errors. Furthermore, when the time constant is increased, the pulse signal is output with almost no deformation, but fluctuations in the baseline are not removed much, and counting errors are still likely to occur.

The object of the present invention is to eliminate the above-mentioned drawbacks and provide a particle counting device that can perform accurate counting.

The present invention will be explained below based on one embodiment shown in FIGS. 2 and 4. In Fig. 2, 4 is a detector, which is provided with a fine hole, and a suspension in which particles are suspended is forced to pass through this fine hole, and the electrical impedance of the suspension and particles is measured. Particles are detected based on the difference between them. A detection circuit 6 converts the signal detected by the detector 4 into an electrical signal. This electric signal generates a pulse signal 1 every time a particle is detected, as shown in FIG. 8 is a time constant circuit that differentiates the output of the detection circuit 6, the details of which will be described later. 10 is a threshold circuit which has threshold values V1 and V2 corresponding to the upper and lower limits of platelets, and outputs an output when the output of the time constant circuit is within the range of V1 and V2 to discriminate platelets. It is. 12 is a counting circuit that counts the output of the threshold circuit 10; 14 is a gate circuit that measures the amount of suspension detected by the detector 4, and starts the counting circuit 12;
This is for sending gate signals such as stop.

The time constant circuit 8 has a time constant switching circuit 16 as shown in FIG. This time constant switching circuit 1
Reference numeral 6 includes a differential circuit consisting of a capacitor 18 and resistors 20 and 22, the time constant of which is changed by switching a changeover switch 24. When the switch 24 is switched to the resistor 20 side, the time constant is small, for example, several hundred microseconds, and when it is switched to the resistor 22 side, the time constant is large, for example, several milliseconds.

26 is a differentiating circuit which differentiates the output of the detection circuit 6 which is inputted through the buffer amplifier 28, and has a small time constant, and produces a sharp pulse with opposite polarity at the beginning and end of the pulse signal 1 shown in FIG. Generate a signal. Reference numeral 30 denotes a comparison circuit which outputs an output when the output of the differentiating circuit 26 is positive. 32 is also a comparison circuit, which outputs an output when the output of the differentiating circuit 26 is negative. Reference numeral 34 denotes an RS flip-flop, which controls switching of the switching circuit 24 based on the outputs of the comparison circuits 30 and 32.

The particle counting device configured in this manner operates as follows. Now, the output of the RS flip-flop 34 is "0", and the changeover switch 24 is connected to the resistor 20.
It is assumed that the time constant of the time constant switching circuit 16 is decreased.

In this state, when the detector 4 starts suctioning the suspension, the gate circuit 14 activates the counting circuit 12. At this time, assuming that the particles have not passed through the micropores and that external noise etc. are occurring,
As shown in FIG. 1, the output of the detection circuit 6 has a raised baseline 2, but since the time constant of the time constant switching circuit 16 is small, the time constant switching circuit 1
The output of No. 6 is flat as shown in FIG. When a particle passes through the fine hole in this state and pulse signal 1 rises, the output of the differentiating circuit 6 becomes a positive pulse, and the comparator circuit 30 inputs the output "1" to the RS flip-flop 34. Then, the output of the RS flip-flop 34 becomes "1", the changeover switch 24 is switched to the resistor 22 side, the time constant of the time constant changeover circuit 16 becomes large, and the output becomes a pulse signal as shown in FIG. This results in a pulse signal 36 having approximately the same magnitude as 1. When the pulse signal 1 falls, the output of the differentiating circuit 26 becomes negative, the output of the comparator circuit 30 becomes "0", the output of the comparator circuit 32 becomes "1", and the output of the RS flip-flop 34 becomes "0".
The output becomes "0", the changeover switch 24 is switched again to the resistor 20 side, and the time constant changeover circuit 16 is switched to the resistor 20 side again.
The time constant becomes small again, and the baseline portion becomes flat. The output of the time constant circuit 8 as shown in FIG. 4 is input to a threshold circuit 10, and the threshold circuit 10 emits an output every time a pulse signal within the range of an upper limit value V1 and a lower limit value V2 is input, Counting circuit 12 counts its output. When the detector 4 suctions a predetermined amount, the gate circuit 14 sends a stop signal to the counting circuit 1.
2 and the counting ends.

This particle counter includes a detection circuit 6 and a threshold circuit 1.
0, the time constant is made small in the baseline part of the output of the detection circuit 6, and the time constant is made large in the pulse signal part, so the output of the time constant circuit 8 is the same as the baseline part. is always flat, and the pulse signal portion becomes almost the same signal as the input pulse signal. Therefore, discrimination and counting by the threshold circuit 10 and the counting circuit 12 are performed accurately.

In the above embodiment, the gate circuit 14 is configured to control only the counting circuit 12, but it may also be configured to control the detection circuit 6, time constant circuit 8, and threshold circuit 10.

[Brief explanation of the drawing]

Fig. 1 is a particle detection signal waveform diagram of a conventional particle counting device, Fig. 2 is a block diagram of a particle counting device according to the present invention, Fig. 3 is a block diagram of a time constant circuit of the particle counting device, and Fig. 4 is a block diagram of a particle counting device according to the present invention. FIG. 3 is an output waveform diagram of the time constant switching circuit of the simultaneous constant circuit. 4...Detector, detection device, 6...Detection circuit, detection device, 10...Threshold circuit, 12...Counting circuit, 1
6...Time constant switching circuit (variable time constant differentiating circuit),
26...differentiation circuit, rise and fall detection section, 3
0, 32... Comparison circuit, rising and falling detection section, 34... RS flip-flop (control circuit).

Claims (1)

[Claims] 1. A detection device that generates a pulse signal when detecting the particles based on the difference in electrical impedance between the particles and a liquid that suspends the particles, a threshold circuit that discriminates the output signal of this detection device, and a threshold circuit that discriminates the output signal of this detection device. a circuit for counting output, a variable time constant differentiating circuit is provided between the detection device and the threshold circuit, and a rising portion detection circuit and a falling portion detection circuit are provided for the pulse signal. A particle counting device comprising: a control circuit that increases the time constant of the differentiating circuit based on the output of the rising edge detection circuit and reduces the time constant of the differentiating circuit based on the output of the falling edge detection circuit.