JPS6246822B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sensitivity adjustment device for a photometric system in a spectroscopic analyzer.

In conventional spectroscopic analyzers, the sensitivity of the photometric system is adjusted by manually adjusting variable resistors and the like while viewing the display. The present invention has been made with the object of making it possible to automatically perform such manual sensitivity adjustment with a single touch.

In order to specifically explain the purpose of the present invention, a conventional example shown in FIG. 1 will be described. Figure 1 shows an atomic absorption spectrometer, where HCL is the light source emitting the bright line of the element to be detected, ATM is the flame of the sample atomization section, MC is the spectrometer, PM is the photomultiplier of the photodetector, PA is a preamplifier, LOG is a logarithmic converter that converts the photometric output into an absorbance value, M is a display section, and DD is a DC-DC converter that applies a high voltage to the dynode of the detector PM, which adjusts the variable resistor VR1. The sensitivity of the detector PM is adjusted accordingly. In this adjustment procedure, turn on the light source HCL, match the wavelength of the spectrometer to the desired emission line wavelength without supplying a sample, adjust the slit width, and then adjust VR1 so that the LOG output Vo becomes approximately 0. . Such adjustment is to set the input Vi to the absorbance converter LOG within a range where the linearity of the converter is good, and furthermore, it is desirable that the display M shows 0 in a state where there is no absorption. It is from. However, it is extremely troublesome to manually perform each such adjustment by relying on visual inspection prior to spectroscopic analysis. The present invention allows the above-mentioned sensitivity adjustment to be performed automatically by simply operating a switch. Furthermore, background correction can be performed at the same time. The present invention will be explained below with reference to Examples.

FIG. 2 shows an embodiment of the present invention. Components that are the same as those in FIG. 1 are given the same reference numerals as in FIG. 1, and detailed description thereof will be omitted. First, only the operation of the sensitivity control system will be explained. D is a continuous spectrum light source for background correction, which is turned on alternately with the bright line light source HCL by the power source LP.
The output of the preamplifier PA, that is, the photometric output Vi, is selected by the signal selector DC when the continuous spectrum light source is turned on, and the preamplifier PA output when the continuous spectrum light source is turned on is output to the absorbance converter LOG ₂ .
and one input terminal of the error amplifier EA. The other input terminal of the error amplifier has a reference voltage.
Vr is applied. SH is a sampling hold circuit, and Sw1 is a sampling switch. The output of the sampling and holding circuit SH is converted into a DC high voltage by a DC-DC converter DD and applied to the dynode of the detector PM. Therefore, when the switch Sw1 is closed, the photometric output Vi is compared with the reference voltage Vr, and the difference between the two is fed back to the detector PM via the DC-DC converter DD, so that Vi becomes equal to Vr. . Vr is set so that the output of the absorbance converter LOG becomes 0 when Vi=Vr.

With the above configuration, sensitivity adjustment is performed as follows.
Turn on the light source HCL and adjust the wavelength and slit width of the spectrometer MC. Up to this point, there is no difference from the conventional device. During this time, switch Sw1 is turned on. As a sensitivity adjustment operation, it is sufficient to simply turn off Sw1 after this. Initially, switch Sw1 is on, so the photodetector PM outputs photometry after the spectrometer MC's wavelength matching and slit width adjustment are completed.
The voltage applied to the dynode is adjusted so that Vi is equal to the reference voltage Vr, and the DC-DC converter
The input voltage of DD is stored in capacitor C of sampling hold circuit SH. Therefore, even if switch Sw1 is subsequently opened, the PM sensitivity is maintained at the sensitivity immediately before opening Sw1, and in this state, Vi
= Vr. Vr is the output of absorbance converter LOG is Vi
Since it is set to be 0 when = Vr,
With the above operations, the necessary adjustments are automatically completed, and all you have to do is turn on/off the switch Sw1, and there is no need to adjust the variable resistor VR1 shown in Figure 1 so that the display shows 0. be.

Next, the configuration and operation of background correction will be explained. That is, in the present invention, the emission line spectrum light source HCL
In addition, a continuous spectrum light source D is used to perform background correction. The light from these two light sources travels on the same optical path through the half mirror HM, passes through the sample atomization unit ATM, the spectrometer MC, and enters the photodetector PM. The half mirror HM has a ratio of transmittance and reflectance that changes in the circumferential direction, and by changing the angular position of rotation, the ratio of light from both light sources can be changed. MT is a motor for changing the angular position of half mirror HM. LP is a lamp power supply that turns on the two light sources alternately and is controlled by a signal from an oscillator OSC. DC is controlled by the output signal of the oscillator OSC by a signal selector, and the output (photometric output) of the preamplifier PA is separated into eH, which is caused by the HCL light, and eD, which is caused by the D light. eH and D are converted into absorbance values eHL and eDL by absorbance converters LOG1 and LOG2, respectively, and are subtracted by a subtraction circuit SUB1, and the background-corrected absorbance values are displayed on display section M1.

SH is a sample hold circuit, but switch Sw1 is not manual but beam balance control part BBC
It is automatically operated by command signals from. error amplifier
EA is the photometric output eD of the continuous spectrum light source D.
is input and compared with the reference voltage Vr. Therefore, the sensitivity of the photodetector PM is adjusted so that eD=Vr. The output Vo of the subtractor SUB1 is applied to comparators CP1 and CP2 and compared with reference voltages +Vcr and -Vcr. CP1 outputs 1 when input Vo is Vo>+Vcr, otherwise outputs 0, CP2 outputs 1 when input Vo is Vo<-
When the voltage is Vcr, the output is 1, and otherwise the output is 0. Therefore, when −Vcr≦Vo≦Vcr, the outputs of CP1 and CP2 are both 0o, and the beam balance control unit BBC outputs CP1 and CP2.
The angular position of the half mirror HM is set by driving the motor MT so that the outputs of the two outputs are both 0, that is, −VcrVo≦Vcr. Half mirror as mentioned above
Since the ratio of transmittance and reflectance of HM changes in the circumferential direction, this operation adjusts the absolute value of the output Vo of the subtracter SUB1 to be equal to or less than Vcr. This operation balances the light from the two light sources so that when no sample is supplied, the photometric outputs of the light from the bright line light source HCL and the light from the continuous spectrum light source D are approximately the same, and the absorbance signal becomes 0.
The switch Sw2 is a manual switch that starts the operation of the beam balance controller BBC.

FIG. 3 is a flowchart of the operation of the beam balance control section BBC. The equipment operator turns on the two light sources HCL and D, sets the wavelength of the spectrometer M, and adjusts the slit width, then turns the switch Sw.
Just press 2. Switch Sw2 on (3rd
Sampling switch Sw1 of the sample-and-hold circuit SH is turned on by (a) in Fig. 3 (b) of Fig. 3.
In judgment C, each output Vc of comparators CP1 and CP2
It is judged whether both 1 and Vc2 are 0 or not. If the judgment is NO, rotate the half mirror HM (Fig. 3 D), and when the judgment C becomes YES, turn off Sw1 (Fig. 3 E) and turn on the sample hold circuit SH. Put it on hold. This completes the operation of the BBC and the sensitivity adjustment of the analyzer.

In the above operation, eD = Vr only for the absorbance converter LOG2 for the photometric output eD of continuous spectrum light.
The feedback circuit is configured so that eH is approximately equal to eD when no sample is supplied by the beam balance operation, so in this case eH is also approximately Vr. ing. Therefore, Vr is converted into absorbance converter LOG1, LOG2
By selecting the ranges with the best linearity for each, optimal sensitivity adjustment can be made for both LOG1 and LOG2. Furthermore, in this embodiment, feedback is performed on eD, but it may be configured to perform feedback on eH.

The subtractor SUB2 is used to calculate the difference between eDL and eDLo and display it on the display section M', and eDLO is eD=Vr.
This is the output of LOG2 when the adjustment operation is completed, and the display of M' becomes 0.

The device of the present invention has the above-mentioned configuration, and can extremely easily adjust the sensitivity of the spectrophotometer by simply turning the switch on and off, without having to operate while visually checking the display, and can also perform background correction at the same time. This makes it possible to reduce the burden on the operator and improve the efficiency of analysis work.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional example, FIG. 2 is a block diagram of an apparatus according to an embodiment of the present invention, and FIG. 3 is a flowchart showing the operation of the apparatus shown in FIG. PM...Photodetector, LOG...Absorbance converter, M
...Display unit, EA...Error amplifier, SH...Sample hold circuit, Sw1...Sampling switch, DD...DC-DC converter, HCL...Emission line spectrum light source, ATM...Sample atomization unit, MC... …
Spectrometer, D... Continuous spectrum light source, BBC...
Beam balance control section, SUB1, SUB2...Subtractor.

Claims (1)

[Claims] 1. An emission line spectrum light source, a continuous spectrum light source, and means for time-sharing the luminous flux from both light sources;
means for guiding the light from both light sources onto the measurement optical path while arbitrarily changing the light intensity ratio; means for detecting the light from both light sources in synchronization with the time division; and converting the detection signals of the light from both light sources into absorbance. and means for subtracting both absorbance signals, and an error amplifier for comparing the detection signal of one of the two absorbance signals with a reference value, and the output of the amplifier is inputted via a sampling switch. A feedback circuit is constituted by a sampling and holding circuit, and the sensitivity of the photodetecting means is controlled by the memory signal of the sampling and holding circuit, and the output signal of the subtraction means is compared to see if it is within a standard. A spectroscopic analysis apparatus characterized in that a feedback circuit is constituted by the means, and the means for arbitrarily changing the light quantity ratio is controlled by the output signal from the comparison means which is manually activated.