JPH0254492B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a trace component detection device that accurately and quickly detects a trace amount of a component to be measured mixed into a liquid, and is particularly suitable for use in an artificial dialysis machine. The present invention relates to a trace component detection device that detects trace amounts of blood leaking into dialysate.

<Prior Art> As a conventional example of such a trace component detection device, there is a blood leakage detection device described in Japanese Patent Application Laid-Open No. 10196/1983. This blood leak detection device includes first and second light emitting elements each having a wavelength peak within a predetermined wavelength range, and light emitting element means for alternately driving these two types of light emitting elements with a constant current according to a reference signal. , a measurement cell for guiding the sample arranged at the light transmission position of the two types of light emitting elements, and first and second measurement cells facing the two types of light emitting elements and arranged close to the measurement cell, respectively. a light receiving element; means for adjusting the balance between the output of the light receiving element by the first light emitting element and the output of the light receiving element by the second light emitting element in a state where there is no blood leakage;
means for detecting an unbalanced component between the output of the light receiving element by the light emitting element and the output of the light receiving element by the second light emitting element; is configured so that it is emitted. In addition, the method uses the unbalanced component detection means to detect the difference in the amount of light reaching the first and second light receiving elements, and when blood leakage occurs, the balance is lost and the light receiving side becomes positive. When a bubble is detected and appears, light scattering by the bubble is captured and detected as a negative value.

<Problems to be Solved by the Invention> However, in conventional examples having the above configuration, LEDs that emit green light and red light, respectively, are often used as the first and second light emitting elements. There were such shortcomings. That is, first, the green light and red light have the disadvantage that the luminous efficiency decreases as the temperature of the LED increases, and the amount of light emitted from the light emitting element decreases as the temperature increases. Second, because the temperature coefficients differ between the green light and the red light, an imbalance occurs in the degree of reduction in light intensity, which makes it difficult to distinguish it from the signal and reduces measurement accuracy. Ta. Thirdly, when the measurement cell is irradiated with the green light and red light, the component to be measured (blood) flowing within the measurement cell is turbid due to its blood cell components, so not only the green light but also some of the red light However, the detection sensitivity of the component to be measured is insufficient simply by taking the difference between the absorption of green light and red light. Fourth, since the absorption of green light and red light is attenuated according to Lambert-Beer's law, there is a drawback that when the amount of attenuation increases, the output of the light receiving element also exhibits nonlinearity and saturates.

<Problems to be Solved by the Invention> The present invention has been made in view of the drawbacks of the conventional examples, and its purpose is to accurately and quickly detect a minute amount of a component to be measured mixed into a liquid. I can,
Another object of the present invention is to provide a trace component detection device that is stable with respect to temperature and can provide an output with excellent linearity with respect to the concentration of the component to be measured.

<Means for Solving the Problems> A feature of the present invention that solves the above-mentioned problems is a trace component detection device that is used in an artificial dialysis machine and detects a trace amount of blood leaking into the dialysate. , an absorption cell in which a liquid containing a trace amount of a component to be measured flows, and two types of light, one with a wavelength that is easily absorbed by the component to be measured, and the other with a wavelength that is difficult to be absorbed by the component to be measured.
a light emitting section that emits colored light, a light receiving section that detects the light emitted from the light emitting section and transmitted through the absorption cell, and outputs an output voltage or output current proportional to the amount of detected light; An integrator whose outputs are alternately applied with opposite polarities via a changeover switch, and a clock pulse oscillator which supplies a clock pulse for determining the period of pulse width modulation to the integrator, By controlling the switching time of the changeover switch, a pulse width signal corresponding to the concentration of the component to be measured is obtained.

<Operation> The present invention operates as follows. That is, first, a LOW waveform signal is output from the comparator, and each switch is activated by this output signal.
Connected to LOW state. In this state, light emitted from the first light emitting element passes through the measurement cell, reaches the light receiving element, and is detected. The detection signal is amplified by an operational amplifier and then input to the inverting input terminal of the operational amplifier via a switch and a resistor. A clock signal from a clock pulse oscillator is also input to the inverting input terminal of the operational amplifier via a resistor. The signals thus input to the inverting input terminal of the operational amplifier are summed and integrated by an integrator consisting of a capacitor and an operational amplifier to become an output signal. This output is output as an output signal of the device according to the invention. The output signal of the integrator may be input to the inverting input terminal of the comparator and compared with a reference voltage, and then become the output signal of the device according to the present invention.

On the other hand, when a HIGH waveform signal is output from the comparator, the switch is switched to the opposite connection state by the output signal. Therefore, the measurement cell is irradiated with light emitted from the second light emitting element, and this light is transmitted through the measurement cell, reaches the light receiving element, and is detected. The detection signal is amplified by an operational amplifier, then passed through a switch, inverted and amplified by an inverting amplifier, then inputted to the inverting input terminal of the operational amplifier via a resistor, and summed and integrated by an integrator consisting of a capacitor and an operational amplifier. becomes the output signal. The output of the integrator is output as the output of the device according to the invention. The output signal of the integrator may be input to the inverting input terminal of the comparator and compared with a reference voltage, and then become the output signal of the device according to the present invention.

<Example> The present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic explanatory diagram of an example of use of an embodiment of the present invention,
In the figure, 1 is a human body, 2 is an artificial kidney dialysis machine, 3a,
3b is a blood circuit that transports blood between the human body 1 and the artificial kidney dialysis device 2; 4 is the artificial kidney dialysis device 2;
There is an embodiment of the present invention that detects minute amounts of blood leaked into the dialysate by attaching the dialyzer to the dialysate. Furthermore, Example 4 of the present invention
A measuring cell is provided inside the measuring cell, and the dialysate dialyzed by the dialyzer is introduced into the measuring cell. Further, the mounting position of the fourth embodiment of the present invention is not limited to the position shown in FIG. 1, and for example, parts other than the measurement cell may be provided separately from the artificial dialysis apparatus 2. Further, the fourth embodiment of the present invention is not limited to the blood leakage detection device as described above, but can be used as various detection devices for detecting trace amounts of components to be measured mixed into liquid.

Further, FIG. 2 is an explanatory diagram of the main part electric circuit of the embodiment of the present invention, and in the figure, 5 to 7 are first to third changeover switches (hereinafter simply referred to as "switches"), 8
9 is a first light emitting element that emits light of a wavelength that is difficult to absorb by the component to be measured (e.g., red light); 9 is a second light emitting element that emits light of a wavelength that is easily absorbed by the component to be measured (e.g., green light); 10 is a light receiving element through which the light emitted from the first and second light emitting elements 8 and 9 passes through the measurement cell, 11 and 13 are operational amplifiers, 12 is an inverting amplifier, 14 is a comparator, and R ₁ ~ _R4 is a resistor, _C1 is a capacitor, and CL is a clock pulse oscillator. In FIG. 2, an integrator is configured by an operational amplifier 13 and a capacitor _C1 , and the output of the integrator is used to switch the first to third switches 5 to 7 via a comparator 14. There is. Further, the period of pulse width modulation in the integrator is determined by a clock pulse supplied from a clock pulse oscillator CL. On the other hand, FIG. 3 is a time chart showing the operation of the embodiment of the present invention (that is, the operation of the electric circuit shown in FIG. 2).
a to e indicate the waveforms of the signals in a to e of FIG. 2, respectively.

Hereinafter, the operation of the embodiment of the present invention will be explained using FIGS. 2 and 3. In FIG. 2, the comparator 14 first outputs a LOW waveform signal (state (i.e., LOW state). In this state, light (for example, green light) emitted from the second light emitting element 9 passes through a measurement cell (not shown) (to which the dialyzed liquid is guided), reaches the light receiving element 10, and is detected. Ru. The detection signal is amplified by the operational amplifier 11, then inverted and amplified by the inverting amplifier 12 via the switch 7 to produce the signal in state X in FIG. 3b (i.e. -
V _G ) and is input to the inverting input terminal of the operational amplifier 13 via the resistor R ₄ . Also, operational amplifier 1
The clock pulse oscillator is connected to the inverting input terminal of 3.
A clock signal a (clock pulse in state X in FIG. 3a) is also input from CL via resistor _R3 . The signals input to the inverting input terminal of the operational amplifier 13 in this way are summed and integrated by the integrator consisting of the capacitor _C1 and the operational amplifier 13 to become the output signal d, which has a waveform in state X in FIG. 3d. The signal will be as shown in . The output signal d
is input to the inverting input terminal of the comparator 14 and compared with the reference voltage, resulting in an output e, resulting in a signal as shown by the waveform in state X in FIG. 3e. This output e is the output signal of the device according to the present invention.
Output as OUT.

On the other hand, when a HIGH waveform signal (the waveform signal in state Y in FIG. 3e) is output from the comparator 14, the output signal causes the switches 5,
6 and 7 are respectively switched to the connection state shown in FIG. Therefore, the measurement cell is irradiated with light (for example, red light) emitted from the first light emitting element 8, and this light passes through the measurement cell, reaches the light receiving element 10, and is detected. . The detection signal is amplified by the operational amplifier 11 and then passed through the switch 6 to become a signal as shown in the waveform in state Y in FIG. 3c. This signal is then input to the inverting input terminal of the operational amplifier 13 via the resistor R ₂ and compared with the reference voltage to produce the output e, resulting in a signal as shown in the waveform for state Y in Figure 3e. Become. This output e is output as the output signal OUT of the device according to the invention.

By the way, the clock pulse generator CL supplies the clock pulse that determines the period T of pulse width modulation to the integrator, and the clock signal a (clock pulse) sent from the clock pulse generator CL is shown in FIG. 3a. It has become a complete exchange. For this reason, the clock pulse generator CL
When the clock signal a sent from the integrator is integrated by the integrator, the value of the integration over one period (T) becomes zero. Further, the signal transmitted via the second switch 6 and the output signal of the operational amplifier 12 are fed back so that the integral value of one period by the integrator becomes zero. Therefore, the areas of the shaded portions in FIGS. 3b and 3c are equal, and the following formula (1) holds true.

V _G・T _{X = V R ・ (} T− _T
The following equations (2) and (3) are derived from equation (1).

T _X /T ₌ V _R /(V _G + _{V R} ) _... (2) ₍ T-T ), T is the period of the clock signal and is constant. _{Therefore , by} measuring T _X or ₍ T- _T This ratio corresponds to the blood leakage concentration (ie, the concentration of the component to be measured) in the dialysate flowing within the measurement cell. Further, T _X is obtained by directly measuring the clock using a counter using the output of the comparator 14 as a gate.

Further, the above circuit operation will be explained in more detail as follows. First, if the waveform section t _i to t _j in Fig. 3 is represented by t _i t _j , then between t ₁ t ₂ it will be as follows, and between t ₂ t ₃ it will be as follows,
Between t _{3 and} t ₄ , it becomes as follows, and between t ₄ and t ₅ it becomes as follows. That is, the input to the integrator is
The signals from CL are -V _C and -V _G. Therefore, the integrator is rapidly charged in the positive direction, and t ₁ t ₂ in Figure 3d
Give a waveform signal as shown in the waveform between. The inputs to the integrator are the signals +V _C and -V _G from clock CL.
It is. Here, since |V _C |>|V _G |, the output of the integrator is integrated in the negative direction. Therefore, the output of the integrator is directed toward OV (zero volts) as shown in Fig. 3d.
Give a waveform signal as shown in the waveform between t ₂ t ₃ .
When the output of the integrator reaches zero, switches 5 to 7 are switched and the inputs of the integrator become the signals +V _C and +V _R from the clock CL. Therefore, the output of the integrator is integrated more rapidly (ie, with a steeper slope) in the negative direction than during t ₂ t ₃ . Therefore, the output of the integrator goes in the negative direction and provides a waveform signal as shown by the waveform between t ₃ and t ₄ in FIG. 3d. The inputs of the integrator are the signals -V _C and +V _R from clock CL.
Here, since |V _C |>|V _R |, the output of the integrator is integrated in the positive direction. Therefore, the output of the integrator is
A waveform signal as shown in the waveform between t ₄ and t ₅ in FIG. 3d is given in the OV direction. In addition, the clock signal CL
Since the output signal is alternating current, the integral value for one period is zero. Also, the area of the shaded area in Figure 3b (i.e., the product of V _G and T _X ) and the area of the shaded area in Figure 3c (i.e., the product of V _R and T - _T Since they are integral values for one period, they are the same. Therefore, the above equation (1) holds true.

Next, we will explain that t ₁ t ₅ always coincides with the period T of the clock signal (that is, the signal whose waveform is shown in FIG. 3a). That is, the peaks of the waveform in FIG. 3a are +V _C and -V _C , and their absolute values are equal. Here, assuming that T is greater than t ₁ t ₅ , since t ₂ t ₄ = T/2, (t ₁ t ₂ +
t ₄ t ₅ ) becomes smaller than T/2. Therefore, the integration of the negative input decreases, and the output of the integrator shifts to the negative side. Therefore, t ₅ of the waveform in Figure 3a
The point will be on the negative side, and the switch will remain in that state until the integrator output becomes zero. This means that the time t ₅ in FIG. 3d is extended. On the other hand, assuming that T is smaller than t ₁ t ₅ , since t ₂ t ₄ =T/2, (t ₁ t ₂ +t ₄ t ₅ ) will be larger than T/2. For this reason, the integration of the negative input increases and the output of the integrator shifts to the positive side. Therefore, the _t5 point of the waveform in Figure 3 d is on the positive side, and the switch is switched quickly. He should be aware of it. This means that
This means that the time t ₅ in FIG. 3 decreases. Since it is realistically impossible for the time t ₅ in FIG. 3 to increase or decrease in this way, it is incorrect to assume that T is smaller or larger than t ₁ t ₅ . Therefore, T is equal to t ₁ t ₅ and, as a result, t ₂ t ₄ and (t ₁ t ₂ +t ₄ t ₅ ) are both equal to T/2. That is, t ₂ t ₄ , (t ₁ t ₂ + t ₄ t ₅ ), and t ₄ t ₆ are all equal to T/2, which means that t ₁ t ₅ is the clock signal (i.e., the waveform shown in Figure 3a). This means that it always matches the period T of the signal (indicating the signal).

It should be noted that the invention is not limited to the above-described embodiments, and can be modified in various ways, for example, as shown in the following. T _X is obtained as an analog output by switching a predetermined reference voltage on the output of the comparator 14 and taking the average. In artificial dialysis, there is a priming step in which the artificial kidney dialysis device 2 and the blood circuits 3a and 3b are filled with physiological saline, and in this step, dialysate is flowing into the measurement cell of Example 4 of the present invention, and the components to be measured are The concentration of blood is zero. Therefore, in this state, apply auto-zero and memorize the _{time T}
Calculate the blood leakage concentration from the change in . When T = 10 ms, adjust the circuit to about 5 ms as the above time T _X , and when auto zero is applied, the time _T
If the deviation is significantly greater than 5 ms, it is determined that there is dirt on the light input/output window or that the light emitting elements 8 and 9 have deteriorated, and an alarm is issued. Since the output of the integrator switches between positive and negative as shown in FIG. 3d, the comparator 14 is not necessarily necessary in FIG. Make it.

By the way, the first and second light emitting elements 8, 9
light emitted by (e.g. red and green light)
The following equations (4) and (5) hold if the intensities are I _r and I _g, respectively, and the initial values and temperature coefficients of the intensities are I _rp and I _gp , and α _r and α _g, respectively.

I _r = I _rp + α _r・t ... (4) I _g = I _gp + α _g · t ... (5) However, t is the temperature.

Furthermore, the following equations (6) and (7) are derived from the above equations (4) and (5).

I _r −I _g = (I _rp −I _gp ) ・{1+(α _r −α _g )・t/I _rp −I _gp } ...(6) I _g /I _r +I _g = I _gp +l _g・t/(I _rp + I _gp・{1
+(l _r +l _g )・t/(I _rp +I _gp } =l _g /l _r +l _g・{1+I _rp /l _g −(I _rp +I _gp
) / (l _r + lg) / t + (I _rp + I _gp ) / (l _r + l _g )}≒
I _gp / (I _rp + I _gp )・{1+(l _g・I _rp /I _gp −l _r )・t
/(I _rp + I _gp )}...(7) Equations (4) and (5) above respectively represent the detection principle of the component to be measured in the conventional example (a method that takes the difference between red light and green light).
and corresponds to the detection principle of the component to be measured (method of taking the ratio of the sum of red light and green light) of the embodiment of the present invention, but since I _gp ≒ I _rp and the following formula (8) holds, It can be seen that the examples of the present invention are less affected by temperature changes.

l _r −l _g /I _rp −I _gp ≫l _g・I _rp /I _gp −l _r /I _rp +I _gp ……
(8) On the other hand, FIG. 4 is a main part electric circuit diagram showing another embodiment of the present invention. In the figure, 15 is a light source such as a lamp, and 16a and 16b respectively emit only green light and red light. First and second filters for transmitting light; 17a and 17b are first and second light-receiving elements; 18a and 18b are first and second operational amplifiers that amplify respective outputs from light-receiving elements 17a and 17b; 19; 20 is a third operational amplifier, and 21 is a comparator. Further, the third operational amplifier 20 and the capacitor C constitute an integrator, and the output of the comparator 21 can also be used to switch the switch 19. Furthermore,
First and second filters 16a, 16b and light source 1
5 constitutes a light-emitting section, the first light-receiving element 17a and the second light-receiving element 17b constitute a light-receiving section, and a liquid containing a component to be measured is contained in a measurement cell provided between the light-receiving section and the light-emitting section. It is structured so that it flows.

In an embodiment having such a configuration, the light source section simultaneously emits light with a wavelength that is easily absorbed by the component to be measured (for example, green light) and light with a wavelength that is difficult to be absorbed by the component to be measured (for example, red light), These lights are simultaneously received by the light receiving section. Also,
The detection signal sent out from the first light receiving element 17a of these light receiving sections is amplified by the first operational amplifier 18a, and the detection signal sent out from the second light receiving element 17b is amplified by the second operational amplifier 18b. Furthermore, the output of the first operational amplifier 18a and the second operational amplifier 18
The outputs of b are alternately input to the third operational amplifier 20 via the switch 19. Note that 18a and 18b are operational amplifiers that amplify in opposite polarities, for example, 18a amplifies positively and 18b amplifies negatively.

Furthermore, as in the case of the signal processing detailed in FIG. 2, the signal inputted to the third operational amplifier 20 as described above is processed by the switch 19 when the output of the first operational amplifier 18a becomes large. Since the feedback is pulse-modulated once so that the time it is connected to the amplifier 18a is shortened, the same effect as in the embodiment of FIG. 2 is obtained. Therefore, according to the embodiment of FIG. 4, the same effects (to be described later) as the embodiment of FIG. 2 can be obtained with a simpler configuration than the embodiment of FIG. 2. Also,
Since the lamp 15 (for example, a tungsten lamp) is used as a light source and the filters 16a and 16b provide two-color light beams with different wavelengths, it is more resistant to temperature changes than the embodiment shown in FIG. Excellent stability.

Although the embodiment shown in FIG. 4 is not provided with an operational amplifier corresponding to the inverting amplifier 12 shown in FIG. It has the same functions as the embodiment shown in the figure. In addition, the clock pulse generator CL emits pulses at a constant period.
The clock signal sent from the clock pulse generator CL is completely alternating current, as shown in FIG. 3a, and plays the same role as in the embodiment of FIG. 2.

<Effects of the Invention> According to the present invention as described in detail above, the following effects can be obtained. That is, compared to the case of the conventional example, the intensity of the two types of light (for example, green light and red light) emitted from the first and second light emitting elements is significantly less affected by temperature changes. There is no need to perform temperature compensation on light intensity. Even if the light quantity balance of the two types of light is shifted, only the baseline changes. For this reason, changes in the baseline are easily corrected by auto-zero, and the span (so-called measurement sensitivity) hardly changes. If the light input/output window becomes dirty, even if the dirt causes a difference in the absorption of two types of light and the balance is lost, the balance can be easily corrected by auto-zero. Therefore, the measurement sensitivity hardly changes, and it is easy to obtain a correct output that is not affected by dirt adhering to the light input/output window. When the absorption of two types of light is large, in the conventional example, the output is saturated and exhibits nonlinearity, but in the present invention, since the configuration is such that the ratio is taken as described above, the curvature of the output can be easily corrected. Since the output is proportional to the hematric value, which is the volume percentage of blood cell components, it is possible to obtain an output that is not affected by the turbidity content, which varies among individuals, contained in the blood, which is the component to be measured. By detecting that the initial value of time _T
Dirt on the light input/output window can be automatically detected.

[Brief explanation of drawings]

Fig. 1 is a schematic explanatory diagram of an example of use of the embodiment of the present invention, Fig. 2 is an explanatory diagram of the main part electric circuit of the embodiment of the present invention, and Fig. 3
The figure is a time chart showing the operation of the embodiment of the present invention.
FIG. 4 is an explanatory diagram of a main part electric circuit showing another embodiment of the present invention. 1...Human body, 2...Artificial kidney dialysis device, 3a,
3b... Blood circuit, 4... Example of the present invention, 5,
6, 7, 19...Switch switch, 8, 9...Light emitting element, 10, 17a, 17b...Light receiving element, 1
1, 12, 13, 18a, 18b, 20... operational amplifier, 14, 21... comparator, 15...
light source.

Claims (1)

[Claims] 1. An absorption cell in which a liquid containing a trace amount of a component to be measured flows, and two colors of light: light with a wavelength that is easily absorbed by the component to be measured and light with a wavelength that is difficult to be absorbed by the component to be measured. a light emitting part that emits light, a light receiving part that detects the light emitted from the light emitting part and passes through the absorption cell, and outputs an output voltage or output current proportional to the amount of detected light; An integral unit in which an output transmitted from the light receiving section corresponding to the light and an output transmitted from the light receiving section corresponding to the light that is difficult to be absorbed by the component to be measured are alternately applied with opposite polarities to each other via a changeover switch. a clock pulse oscillator that supplies a clock pulse for determining a period of pulse width modulation to an inverting input terminal of an operational amplifier that constitutes the integrator and receives the output of the light receiving section via the changeover switch; A trace component detection device characterized in that a pulse width signal corresponding to the concentration of the component to be measured is obtained by controlling the switching time of the changeover switch using the output of the integrator. 2. The light emitting section is composed of first and second light emitting elements, and the light receiving section is composed of one light receiving element, and these light emitting elements are alternately switched by a changeover switch that is also switched by the output of the integrator. Claim 1 configured to emit light
The trace component measuring device described in section. 3. The light emitting section includes one light source and first and second filters, and the light receiving section includes first and second filters provided at positions facing the first and second filters, respectively. A trace component measuring device according to claim 1, which comprises a light receiving element.