JPH0566987B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides an input signal suitable for detecting a signal voltage input in a time-division manner through a filter consisting of a resistor and a capacitor provided for noise reduction. This relates to a voltage detection method.

[Conventional technology]

FIG. 3 is a diagram showing an example of a detection system of a colorimetric detector. In the figure, 11 is a light source, 12 is a concave diffraction grating,
13 is a light shutter, 14 and 16 are light guides,
15 is a reaction tube, 17 is a photodiode, 18 is a preamplifier, 19 is a buffer amplifier, 20 is a multiplexer, 21 is a sample hold circuit, 22
2 is an A/D converter, 23 is a data processing device, and 24 is a timing generation circuit.

In recent years, analysis devices equipped with a colorimetric detector, such as automatic biochemical analyzers and liquid chromatographs, have come to obtain colorimetric data at multiple wavelengths from a single test liquid. In the case of such a detector, the third
The system shown in the figure performs everything from colorimetric detection to A/D conversion while switching the wavelength.

An overview of the colorimetric detection system can be explained using Figure 3.
For example, when testing serum, a reagent is mixed with serum obtained by centrifugation and reacted at a predetermined temperature, and the reaction tube 15 is filled with the mixture as a comparison solution.
Light of various wavelengths is emitted from a light source 11 through a concave diffraction grating 12, an optical shutter 13, and a light guide 14. Here, the optical shutter 13 switches the wavelength of the emitted light according to the timing generated by the timing generation circuit 24.

The light of various wavelengths irradiated onto the test liquid in the reaction tube 15 is partially absorbed by the test liquid in the reaction tube 15, and the transmitted light is detected by the photodiode 17 through the light guide 16. The detection signal from the photodiode 17 is sent to a multiplexer 20 through a preamplifier 18 and a buffer amplifier 19, switched to each channel by the multiplexer 20, temporarily held in a sample and hold circuit 21, and sequentially passed through an A/D conversion circuit 22 to a data processing device 23. be taken in. Therefore, in this example, as the optical shutter 13 is switched, data for each specific wavelength regarding each test liquid is obtained.

By the way, in the colorimetric detection system as described above, it has become necessary to construct a detection system with high-speed response in order to obtain data of a large number of wavelengths for a large number of test liquids.
In addition, in order to suppress noise in the detection system, for example, the preamplifier 18 and buffer amplifier 19
It is necessary to connect a so-called CR filter consisting of a resistor capacitor between the

[Problem that the invention seeks to solve]

However, the above CR filter
If the time constant is increased in order to keep noise low, there is a problem that high-speed response cannot be achieved. That is, in the system shown in FIG. 3, when a CR filter with a large time constant is connected between the preamplifier 18 and the buffer amplifier 19, the optical shutter 1
3, it takes a long time to reach an equilibrium state. Therefore, if a CR filter with a time constant commensurate with the responsiveness of the detector is connected, noise above a certain level cannot be suppressed. Therefore, the present inventor shorted both ends of the capacitor of the CR filter for a predetermined time according to the detection timing, then opened both ends of the capacitor, and calculated the input signal voltage based on the time after the capacitor was opened. By doing so, we separately proposed a method that uses a filter with a large time constant to suppress noise and achieve high-speed response. However, even in this case, there is a problem that the detection accuracy of the input signal voltage deteriorates if the time constant of the CR filter changes depending on the temperature.

The present invention solves the above problems and provides an input signal voltage detection method that can detect and capture the input signal voltage with high accuracy even if the time constant of the CR filter changes depending on the temperature. The purpose is to

[Means for solving problems]

For this purpose, the input signal voltage detection method of the present invention is
This is an input signal voltage detection method in which an input signal is passed through a filter consisting of a resistive capacitor and held in a sample hold circuit, and the input signal voltage is taken in based on the held value. The device is characterized in that the output voltages at two points are held for different times with both ends open, and the input signal voltage is calculated and determined based on the output voltages at the two points.

[Effect]

In the input signal voltage detection method of the present invention, both ends of a capacitor constituting a filter are short-circuited for a predetermined period of time,
Since both ends of the capacitor are then opened, the capacitor is charged by the signal input voltage according to the time constant of the filter. Therefore, by holding the output voltages at two points on this charging curve for different times, an accurate input signal voltage can be calculated from the output voltages at the two points and their hold times, with the time constant being an unknown value.

〔Example〕

Examples will be described below with reference to the drawings.

FIG. 1 is a diagram for explaining the input signal voltage detection method of the present invention, and FIG. 2 is a time chart for explaining the hold timing by the input signal voltage detection method of the present invention. 1 is a preamplifier, 2 is a time chart.
CR filter, 3 is buffer amplifier, 4 is multiplexer, 5 is sample hold circuit, 6 is A/
7 is a data processing device, 8 is a timing generation circuit, PD is a photodiode, OP is an operational amplifier, r1, r2, R, VR are resistors, C is a capacitor, and AS is an analog switch.

In FIG. 1, the CR filter 2 is composed of a resistor R and a capacitor C, and an analog switch AS is connected between the terminals of the capacitor C. As mentioned above, it is controlled in synchronization with the switching timing of the optical detection system (optical shutter or optical switch). That is,
The analog switch AS is turned on for a predetermined period of time in synchronization with this timing when the photodetection system is switched, shorting the terminals of the capacitor C and discharging the capacitor C at high speed. Therefore, when the analog switch AS is turned off again after a predetermined period of time, the influence of the previous signal voltage disappears, and the capacitor C is affected by the new signal voltage after switching the photodetection system according to the time constant of the CR filter 2. It will be charged. Note that the timing generation circuit 8 generates operation timing signals for the multiplexer 4, the sample hold circuit 5, and the A/D converter 6 in addition to the photodetection system and the analog switch AS.

Next, a case will be described in which an input signal voltage is taken in in the analyzer equipped with the colorimetric detector shown in FIG. In Figure 1, the analog switch AS is
As mentioned above, it is turned on and off in synchronization with the switching timing of the photodetection system. Therefore, Figure 2a
Corresponding to the on/off mode of the analog switch AS shown in FIG. 2, the CR filter 2 obtains an output voltage with a waveform as shown in FIG. 2b. Therefore, the timing generation circuit 8 generates the analog switch AS.
Based on the point in time when the output voltage is turned off from _on as a reference, the sample and hold circuit 5 and the A/D converter circuit 6 are controlled to hold the two output voltages E ₁ and E ₂ after a time T 1 and then after a time T ₂ respectively. Convert to digital value. Here, the voltages E ₁ and E ₂ are E ₁ = _{E 0 [} 1-exp(-T ₁ /CR)] E ₂ =E ₀ [1 −exp(−T ₂ /CR)] Therefore, the signal voltage E ₀ can be found by simultaneous equations with the time constant (CR value) that changes depending on conditions such as the ambient temperature and the signal voltage E ₀ as unknowns. can. In this case, changes in the time constant due to temperature changes between times T ₁ and T ₂ can be ignored, so even if the ambient temperature changes and the time constant value at that time is constant, the signal voltage E can always be adjusted with high accuracy. You can find ₀ .

Note that the present invention is applicable not only to the detection system of a colorimetric detector but also to other systems that detect a large number of signal voltages by switching the input signal system of a CR filter. Thus, it goes without saying that the present invention is not limited to the above-described embodiments, and that various modifications are possible.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, the analog switch AS is turned on/off in synchronization with the switching timing of the photodetection system, the capacitor C is discharged at high speed, and then the capacitor C is charged with a new next signal voltage. Therefore, it is not affected by the previous signal voltage. Moreover, the output voltage is held at two points on the charging curve according to the time constant of CR filter 2, and the CR
Since the signal voltage on the input side of the filter 2 is calculated and determined, an input signal voltage detector with low noise and high speed response can be provided regardless of changes in ambient temperature.

[Brief explanation of the drawing]

Fig. 1 is a diagram for explaining the input signal voltage detection method of the present invention, Fig. 2 is a time chart for explaining the hold timing by the input signal voltage detection method of the present invention, and Fig. 3 is a colorimetric detector. FIG. 2 is a diagram showing an example of a detection system. 1...Preamplifier, 2 is CR filter, 3...
Buffer amplifier, 4...Multiplexer, 5...
Sample hold circuit, 6...A/D converter, 7
...Data processing device, 8...Timing generation circuit, PD...Photodiode, OP...Operation amplifier, r1, r2, R, VR...Resistor, C...Capacitor, AS...Analog switch.

Claims (1)

[Claims] 1. An input signal voltage detection method in which an input signal is passed through a filter consisting of a resistor and a capacitor and held in a sample-and-hold circuit, and the input signal voltage is taken in based on the held value, wherein both ends of the capacitor are connected for a predetermined period of time. The capacitor is short-circuited, and then both ends of the capacitor are opened to hold the output voltages at two points for different times, and the input signal voltage is calculated and determined based on the output voltages at the two points. Input signal voltage detection method. 2. The input signal voltage detection method according to claim 1, wherein both ends of the capacitor are short-circuited in synchronization with the switching timing of the signal input system.