JPS62215850A - Photometric apparatus for emission spectrum analysis - Google Patents

Abstract

PURPOSE:To attain to perfectly automate the adjustment of sensitivity, by feeding back the detection output of a photomultiplier tube to the voltage applied to the photomultiplier tube and operating a photometric value from the amplifying degree, which is converted using the correlation data of the applied voltage and an amplifying degree, and the detection output. CONSTITUTION:The output of a photomultiplier tube 1 is converted to a voltage signal by a parallel circuit of a resistor R and a condenser C, and the voltage signal is amplified by an amplifier 2 to obtain detection output Va which is, in turn, compared with reference voltage Vb by a differential amplifier 3 and the comparing output is inputted to a negative high voltage power source circuit 4. The voltage Vd applied to the photomultiplier tube 1 is controlled by the output of the circuit 4 and the amplifying degree (f) of the photomultiplier tube 1 is changed. The voltage Vd is converted to a digital value by an A/D converter 5 to be read in a microprocessor 6 and said digital value is converted to the amplifying degree (f) using the correlation data of the voltage Vd and amplifying degree (f) preliminarily stored in a memory. The output Va is divided by the amplifying degree (f) to output a photometric value to an output apparatus 7. By this method, the adjustment of the sensitivity of a photometric apparatus can be automated perfectly.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a photometric device used for emission spectroscopic analysis such as high-frequency plasma emission.

(Prior art) When performing toe analysis of elements contained in a sample by making the sample emit light using high-frequency induced plasma, etc., it is necessary to analyze the elements contained in the sample. It is necessary to set different measurement sensitivities depending on the estimated content. For example, in the device proposed in JP-A No. 59-99336, target values for the measurement output of each element in a standard sample are stored in memory in advance, and a photomultiplier tube is sequentially read out from the memory using a program. This method automatically adjusts the sensitivity of the sample and has the advantage of reducing the operator's workload, but it requires setting a target estimated value for each sample in advance, and the actual content may exceed the estimated range. The disadvantage is that analysis cannot be performed.

(Problems to be Solved by the Invention) The present invention provides a photometric device for emission spectrometry that can always automatically adjust a photomultiplier tube to the optimum sensitivity without setting a target value in advance as described above. The purpose is to

(Means for Solving the Problems) In order to achieve the above object, the photometric device according to the present invention has the following features:
A means for comparing the detection output of the photomultiplier tube with a fixed value or a value in a fixed range, and feeding back the comparison output to the applied voltage of the photomultiplier tube to change the amplification degree of the photomultiplier tube, and the applied voltage The apparatus is equipped with a means for detecting this, converting it into an amplification degree based on pre-stored correlation data between the applied voltage and the amplification degree, and calculating a photometric value as a ratio of the detection output and the amplification degree.

(Function) According to the above configuration, the amplification degree of the photomultiplier tube is controlled steplessly and the optimal sensitivity is always maintained for optical input, so that measurement can be performed according to the input level as in the conventional method. There is no need to switch ranges, and the SN ratio is improved.

(Embodiment) FIG. 1 shows an embodiment of the present invention, in which the output of a photomultiplier tube I is converted into a voltage signal by a parallel circuit of a resistor R and a capacitor C, and then amplified by an amplifier 2. The obtained detection output Va is compared with a reference voltage vb by a differential amplifier 3, and the output of the differential amplifier 3 is inputted to a negative high voltage power supply circuit 4, thereby controlling the voltage Vd applied to the photomultiplier tube 1. The amplification degree r(v) of the photomultiplier tube l is changed. Further, the applied voltage Vd of the photomultiplier tube 1 is converted into a digital value by the A/D converter 5 and read into the microprocessor 6, and this is stored in the memory in advance as the applied voltage Vd and the amplification degree f (V). The detected output Va is divided by the amplification degree f(V) to calculate the photometric value. The photometric values obtained in this way are output to an output device 7 such as a CRT or pen recorder.
is output to.

FIG. 2 shows the correlation characteristic between the applied voltage Vd and the amplification factor f(V), and this characteristic is stored in advance in the memory of the microprocessor 6 as a function equation or a conversion table.

With this configuration, the sensitivity of the photomultiplier tube 1 is continuously controlled so that the detection output Va is always constant according to the magnitude of the optical input. There is no need to define a measurement range for each element, or to switch the measurement range step by step by detecting overscale of detection output.
There is also the advantage that the N ratio is always kept at its highest.

Figure 3 shows another example, a photomultiplier tube! A negative high-voltage power source 4 inputs the output of
D/A the output data Do from the microprocessor 6
A correlation table between the output data Do and the amplification factor f(V) of the photomultiplier tube 1 is stored in the microprocessor 6, and the microprocessor 6 inputs the data from the A/D converter 8. The output data Do is varied until the input data Di falls within a predetermined range, and the photometric value is calculated by dividing the input data Di by the amplification r(v) of the photomultiplier tube l at this time. It is something.

With this configuration, it is possible to obtain a resolution equal to the number of bits added by the A/D converter 8 and the D/A converter 9 as a photometric value, and the number of significant digits is always the same regardless of the magnitude of the optical input. An additional point is that it allows measurements with a wide dynamic range.

(Effects of the Invention) As described above, according to the present invention, the sensitivity of the photomultiplier tube is controlled by applying feedback to the voltage applied to the electron multiplier tube so as to keep the detection output of the photomultiplier tube constant. With,
This applied voltage is detected, and this is converted into an amplification degree using the correlation data between the applied voltage and the amplification degree, and the photometric value is calculated from the detected output and the amplification degree. There is no need to estimate the amount of each element in the sample and set the sensitivity for each element in advance, making it possible to completely automate sensitivity adjustment and maintain a good signal-to-noise ratio over a wide dynamic range. There are advantages.

[Brief Description of the Drawings] Fig. 1 is a block diagram showing one embodiment of the present invention, Fig. 2 is a characteristic diagram showing the same operation as above, and Fig. 3 is a block diagram showing another embodiment of the present invention. be. DESCRIPTION OF SYMBOLS 1... Photomultiplier tube, 2... Amplifier, 3... Differential amplifier, 4... Negative high voltage power supply, 5... A/D converter,
6...Microprocessor, 7...Output device, 8.
...A/D converter, 9...D/A converter.

Claims (1)

[Claims] (1) A means for comparing the detection output of the photomultiplier tube with a reference value and feeding back the comparison output to the applied voltage of the photomultiplier tube to change the amplification degree of the photomultiplier tube, and detecting the applied voltage. and converting this into an amplification degree using pre-stored correlation data between the applied voltage and the amplification degree, and calculating a photometric value as a ratio between the detected output and the amplification degree. Photometric device for emission spectrometry.