JPS62179635A - Photometer - Google Patents

Abstract

PURPOSE:To enable the securing of a density measuring range as specified even when a light source different in the energy is exchanged, by determining a reference current value of LOG amplifiers from an input value to be supplied to respective LOG amplifiers. CONSTITUTION:Among a plurality of LOG amplifiers 13, an output of one LOG amplifier is supplied to a fixed contact (B) of a change-over switch 24 via an automatic adjustment circuit 23. Whenever a sample such as water is introduced into a measuring cell 11, the circuit 23 starts by an adjustment command signal ST from a microcomputer 16 to hold A/D converted value AB within 0-1V where water or a blank sample is in the cell 11. As a results, a reference current IR to be inputted into the respective LOG amplifiers 13 is set from an output value of the amplifiers 13 with the circuit 23.

Description

[Detailed Description of the Invention] [Industrial Application Field] The photometer of the present invention is particularly applicable to clinical blood automatic analyzers that can quickly measure a large number of items at multiple wavelengths, and measure concentrations with high resolution and over a wide range. Concerning a preferred photometer.

[Prior art]

A conventional photometer that measures multiple items and multiple wavelengths.

In particular, a photometer for a clinical blood automatic analyzer will be explained with reference to FIGS. 2 to 5. First, in Fig. 2, optical system 1
is light source 2. Lens 3, lens 4, slit plate 5. An entrance slit 6, an exit slit 7, a concave diffraction grating 8. It consists of a semiconductor photodetector 9 and a measurement cell 11 made of glass. On the other hand, the electrical system includes an OG amplifier 13 in the LOG amplifier section 1 and 2, a multiplexer 14, an A/D converter 15, a microcomputer 16. Measurement reaction system.

Mechanical interface 1 that operates fi'flo made by a moving mechanism that sequentially moves measurement cells 11 to the optical path of optical system 1
7. The light from the light source 2 is focused by the lens 3 and sent to the measurement cell 11.
pass through. The passed light enters the concave diffraction grating 8 so that an image of the light source is formed on the surface of the entrance slit 6 by the lens 4.

This concave diffraction grating 8 is a dispersion element, and its reflected light, or dispersed light, is sent to each of the photodetectors 9 attached to the slit plate 5 through each of the output slits 7 of the slit plate 5. ing.

The measuring cell 11 contains a sample to be measured, and the moving mechanism device 10 sequentially guides the next measuring cell to the optical path.

On the other hand, the photodetector 9 detects a wavelength of 340 nm + 376 nm + 415 dispersed by the concave diffraction grating 8.
nm, 450 nm, 480 nm,
505 nm.

546nm, 570nm, 600nm, 660nm, each photodetector 9 has a LOG amplifier 1.
3 is connected. An analog signal from one photodetector 9 is selected from the output of the LOG amplifier 13 by a multiplexer 14 composed of an analog switch, and the output thereof becomes an input to an A/D converter 15.

After being converted into a digital quantity by this A/D converter 15, it is appropriately calculated by a microcomputer 16, and the resulting density value is printed by a printer 19 via a printer interface 18.

[Problem that the invention seeks to solve]

Here, details of the LOG amplifier 13 will be explained with reference to FIG. 3. The LOG amplifier 13 has two input terminals, one of which receives the output m current Is of the photodetector. The other terminal has a Zener diode 20
The reference voltage kept constant by the variable resistor 21. A reference current IR adjusted by a resistor 22 is input. The output voltage Eo of this LOG amplifier 13 is expressed by the following equation (1).

Eo=KQogCIR/Is) ・−・・
(1) Here, K is a proportional constant called the decade constant of the LOG amplifier 13, and is 4 in this embodiment. Therefore, every time the current In and the current Is differ by one digit, the output voltage changes by 4 cm. This means that when the absorbance of the sample in the measurement cell 11 changes by 1, the output Eo of the LOG amplifier 13 changes by 4V.

The photocurrent Is from the photodetector 9 when water is placed in the measurement cell 11 takes different values depending on the wavelength, and the change in value is as shown in the fourth WJ. Each curve in this figure shows the spectrum of the maximum and minimum values when 20 light sources 2 were replaced, and it can be seen that there is a change of about twice as much due to the difference in the energy of the light sources 2. On the other hand, LOG
The reference current IR of the amplifier 13 is determined when the output voltage of the LOG amplifier 13 is 2V (absorbance 0) with water in the measurement cell 11.
．． Each LOG amplifier is adjusted so that the output voltage becomes 5 (equivalent to 5). This 2v adjustment is performed because the input range of the A/D converter 15 is Ov to IOV, so when the light source 2 is replaced (without changing the adjustment of R), the A/D converter This is to prevent the input range from exceeding the input range of 15.

After adjusting the LOG amplifier 13 in this way, to actually measure the sample, first put water or a reagent blank into the measurement cell 11 and enter the optical path, set the A/D conversion value to A8, and then A sample containing a known concentration is introduced into the optical path, and that value is set as ARD.Firstly, an unknown concentration, that is, a sample to be measured is introduced into the optical path.

Assuming that the A/D converted value is AH, the microcomputer 16 calculates the concentration Cs of the unknown sample by performing the first-order calculation shown in equation (2).

Cs=C5o(As-Aa)/(AsD-Aa) ・-
...(2) Here, Csn is the concentration of the known sample.

In this state, if the light source 2 is replaced due to its lifespan, etc., and the reference current IF+ is not readjusted (actually, the customer replaces the light source, so it is impossible to adjust the reference current), the 5th
As shown in the figure, when the measurement cell 11 contains water, the A/D conversion value Aa varies from O to 4V, and due to the instrumental error of the light [2], the range Ss for measuring the actual sample is 6V. This means that it is only possible to measure up to 1.5 in terms of absorbance. In other words, no consideration was given to the fact that the measurement range would change significantly due to replacement of light sources with different energies.

An object of the present invention is to provide a photometer that can maintain a predetermined concentration measurement range even when a light source with significantly different energy is replaced due to the lifespan of the light source.

Means for Solving Problems] In order to achieve the object as described above, the present invention includes a sample cell, a light source for transmitting light to the sample cell, and a method for dividing the transmitted light of the sample cell into different spectra. A photometer comprising: a plurality of photodetectors for detecting; a LOG amplifier into which the output of each photodetector is input; and a measuring means for measuring the sample cell using the output from the LOG amplifier; The output value of the LOG amplifier is determined by using the output of one of the amplifiers as an input, determining the reference current value of the LOG amplifier based on the input value, and outputting the reference current value of each LOG amplifier as the respective reference current value. The device is equipped with an automatic adjustment circuit that sets the value to a predetermined value.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of a photometer according to the present invention. In the same figure, parts made of the same material as in FIG. 2 are denoted by the same reference numerals. The implantation, which is different from that shown in Fig. 2, is that each LO
In the wiring that forms the reference current IR of the G amplifier 13,
A changeover switch 24 is provided at the stabilized output portion of the Zener diode 20. This changeover switch 24 has a movable contact on the LOG amplifier 13 side, a fixed contact A on the Zener diode 2o side, and another fixed contact B.

Furthermore, one L out of the plurality of LOG amplifiers 13
The output of the OG amplifier is input to an automatic adjustment circuit 23, and the output of this automatic adjustment circuit 23 is input to a fixed contact B of the changeover switch 24.

The automatic adjustment circuit 23 controls the microcomputer 16 when water or a blank sample is introduced into the measurement cell 11.
However, it is activated by inputting an adjustment command signal ST. By the operation of this automatic adjustment circuit 23, when the inside of the measurement cell 11 is water or a blank sample, the A/D conversion value ΔB is kept within 0 to 1 V.

In this way, the reference current IR input to each LOG amplifier 13 is controlled by the automatic adjustment circuit 23.
Since it will be set based on the output value of 3, the 5th
As shown in the figure, when the measuring cell 11 contains water or a blank sample, the A/D conversion value AR can be kept within 0 to 17.

Therefore, the unknown concentration measurement range SS is 9V even when the light source 2 is replaced, and it is possible to measure up to an absorbance of 2.5. Furthermore, as shown in FIG. 4, even if the light sources with different energies are replaced in the photodetectors 9 arranged differently depending on the wavelength, the difference in output current between the photodetectors is almost the same. , the Kugata signal to the automatic adjustment circuit 23 is the L of the plurality of LOG amplifiers 13.
Since the output signal from the OG amplifier is sufficient, the adjustment by the automatic adjustment circuit 23 can also be made extremely simple.

In this embodiment, a changeover switch 24 is provided to allow manual or automatic operation. I made it possible to do it, but 2
The manual mechanism, i.e. in FIG.

The output of the automatic adjustment port Wr23 may be inputted to the resistor 22 connected to the input side of each LOG amplifier 13 without providing the Zener diode 20, the changeover switch 24.degree., and the variable resistor 21.

〔Effect of the invention〕

According to the photometer according to the present invention, even if a light source with a significantly different energy is replaced, a measurement concentration range can be largely ensured, and the LOG amplifier can always be measured quantitatively.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the LOG amplifier section of a photometer according to the present invention, Fig. 2 is an explanatory diagram showing a simplified bridge construction of the photometer, and Fig. 3 is a circuit diagram of the LOG amplifier section of a conventional photometer. A circuit diagram showing an example, Fig. 4 is a graph showing the change in photocurrent of each photodetector when the light source is replaced, Fig. 5 is a graph showing the measurement range by a conventional photometer, and Fig. 6 is a graph showing the change in photocurrent of each photodetector when the light source is replaced. It is a graph showing a measurement range by a photometer according to the present invention. 9... Photodetector, 13... LOG amplifier, 14...
・A/D conversion book, 15...Microprocessor, 20
... Zener diode, 21 ... Variable resistor, 22
···resistance.

Claims (1)

[Claims] 1. A sample cell, a light source that transmits light through the sample cell, a plurality of photodetectors that separate the transmitted light of the sample cell and detect each spectrum, and a LOG amplifier that inputs the output of each photodetector. and a measuring means for measuring the sample cell using the output from the LOG amplifier, which inputs the output of one of the LOG amplifiers and measures the sample cell based on the input value of the LOG amplifier. The luminous intensity is characterized by comprising an automatic adjustment circuit that sets the output value of the LOG amplifier to a predetermined value by determining a reference current value of the LOG amplifier and outputting it as the reference current value of each LOG amplifier. Total.