JPH0875636A - Electrodeless discharge lamp lighting apparatus for atomic absorptiometer - Google Patents

Abstract

PURPOSE: To realize an electrodeless discharge lamp lighting apparatus, for an atomic absorptiometer, by which reflected power is suppressed even in the initial state of an atomic absorptiometric measurement and by which measuring light of stable brightenss can be generated. CONSTITUTION: In a period in which a modulating signal (d) is not output from a waveform shaping circuit 10, a pseudomodulating signal (c) is supplied to a signal (f) main power amplifier 21 from a pseudomodulating signal generation circuit 17 via a selector circuit 16, and power (g) at 27.12MHz which has been modulated by the pseudomodulating signal (c) is supplied to an electrodeless discharge lamp 1. When the modulating signal (d) is output from the waveform shaping circuit 10, the modulating signal (d) is supplied to the main power amplifier 21 as a signal (f) by means of a changeover signal (e) from a detection circuit 15, and the power (g) which has been modulated by the modulating signal (d) is supplied to the lamp 1. A change in the impedance of an exciting coil for the lamp 1 due to a change from the modulating signal (c) into the modulating signal (d) is small, and it is possible to avoid a drop in the brightness of the lamp due to reflected power at the early stage of a measurement.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device for an electrodeless discharge lamp used as a light source for measurement of an atomic absorption spectrophotometer.

[0002]

2. Description of the Related Art For example, there is an atomic absorption photometer for analyzing elements such as arsenic, antimony and bismuth. An electrodeless discharge lamp (EDL) is used as a light source for measurement of this atomic absorption photometer.
(Electrode less Discharge Lamp)) is used. A coil is wound around the body of this electrodeless discharge lamp, and for example, krypton gas or the like is sealed inside. When power is supplied to the coil wound around the lamp body, the lamp body is turned on.

Light from the electrodeless discharge lamp is passed through a sample that has been burned and atomized, and the passed light is
The photomultiplier is irradiated through a diffraction grating, a polarizer, a chopper means, and the like. This chopper means is for removing the low frequency component due to the fluctuation of the combustion flame of the sample from the measurement light. Then, the electric power supplied to the electrodeless discharge lamp is modulated by the measurement light modulation signal generated from the chopper means.

As an example of the electrodeless discharge lamp, for example,
There is a "microwave discharge light source device" described in JP-A-58-194244. In this microwave discharge light source device, a first electrodeless lamp that is a main light source arranged in a microwave cavity and a second electrodeless lamp for starting assistance that is excited by microwaves and emits ultraviolet rays are provided. Is provided. This second electrodeless discharge lamp
It is placed in a waveguide or microwave cavity. Then, when microwaves are oscillated from the microwave oscillator, the oscillated microwaves are supplied to the microwave cavity through the waveguide. As a result, first, the second electrodeless lamp is started and ultraviolet rays are emitted. Then, the first electrodeless lamp is excited by the ultraviolet rays emitted from the second electrodeless lamp, and the first electrodeless lamp can be easily started by the weak microwave energy. This ensures that the main light source can be started with a simple structure.

An example of a lighting device for an electrodeless discharge lamp is the "electrodeless discharge lamp lighting device" described in Japanese Patent Laid-Open No. 5-275184. The "electrodeless discharge lamp lighting device" described in the above publication is provided with a matching means for performing impedance matching between the high frequency power supply and the lamp load immediately after the lamp is started or due to changes over time. The impedance matching is performed by the change in the relative positional relationship between the lighting coil and the lamp body and the change in the circuit constant of the lighting circuit.

That is, the output signal of the lamp power supply circuit is compared with the reference signal, and the relative position between the lamp body and the lighting coil is changed according to the result of this comparison. Next, the output signal of the power supply circuit is again compared with the reference signal, and the capacitance value of the variable capacitor of the lighting circuit, which is a resonance circuit, is adjusted based on the comparison result. As a result, impedance matching between the high frequency power supply and the lamp load is performed.

[0007]

By the way, in the conventional electrodeless discharge lamp lighting device for an atomic absorption photometer,
After the high frequency power for absorption spectrophotometry is supplied to the electrodeless discharge lamp, at the same time as the measurement start, the modulation signal,
It is supplied to the high frequency power amplifier.

Immediately after the modulation signal is supplied to the high frequency power amplifier and the high frequency power modulated by the modulation signal is supplied to the electrodeless discharge lamp, the impedance of the excitation coil of the electrodeless discharge lamp is unstable. However, the reflected power increases and the brightness of the lamp decreases. Therefore, in the conventional electrodeless discharge lamp lighting device for an atomic absorption spectrophotometer, highly accurate measurement could not be expected in the initial state of atomic absorption spectrophotometry.

Therefore, it is conceivable to apply the "electrodeless discharge lamp lighting device" described in JP-A-5-275184 as an electrodeless discharge lamp lighting device for an atomic absorption photometer. However, even if the lamp lighting device described in the above publication is applied to a lamp lighting device of an atomic absorption spectrophotometer, adjustment time is required for impedance matching such as relative position movement between the lamp body and the lighting coil.
Therefore, immediately after the modulation signal is generated, the impedance of the excitation coil of the lamp is unstable, and highly accurate measurement cannot be expected in the initial state of atomic absorption spectrophotometry.

An object of the present invention is to realize an electrodeless discharge lamp lighting device for an atomic absorption spectrophotometer, which is capable of generating a measurement light with a stable brightness, in which the reflected power is suppressed even in the initial state of atomic absorption spectrophotometry. It is to be.

[0011]

In order to achieve the above object, the present invention is configured as follows. In an electrodeless discharge lamp lighting device for an atomic absorption spectrophotometer that generates a measurement light modulation signal for atomic absorption spectrophotometry, a pseudo modulation signal generation unit that generates a pseudo modulation signal almost similar to the measurement light modulation signal, and an atomic When the measurement light modulation signal is not generated from the absorptiometer, the pseudo modulation signal from the pseudo modulation signal generating means is selected and output, and when the measurement light modulation signal is generated from the atomic absorption photometer, The output selection means for selecting and outputting the measurement light modulation signal instead of the modulation signal and the modulation signal output from the output selection means modulates and amplifies the high frequency power, and the modulated and amplified high frequency power is output. Power amplification means for supplying the electrodeless discharge lamp.

Preferably, in the above electrodeless discharge lamp lighting device for an atomic absorption spectrophotometer, a command value of an output power value of the power amplification means is manually set, and a power value manual setting means capable of outputting and a power amplification means. A predetermined command value output means for outputting a predetermined output power command value, a power command value from the power value manual setting means, and a power command value from the predetermined command value output means, and a power amplifying means. And output power control means for controlling the output power of the power amplification means.

Preferably, in the above electrodeless discharge lamp lighting device for an atomic absorption photometer, the output power control means detects the output power of the power amplification means, and the power detection means detects the power. The power value and the power command value are compared with each other, and the output power of the power amplification means is controlled based on the comparison between the power command value detected by the comparison means and the detected power value.

Preferably, in the above electrodeless discharge lamp lighting device for an atomic absorption photometer, reflected wave power detecting means for detecting reflected wave power of output power from the power amplifying means, and this reflected wave power detecting means. Reflected wave power comparing means for comparing the reflected wave power detected by the above with a predetermined value is further provided, and when the reflected wave power exceeds a predetermined value, the output of the modulated signal from the output selecting means is stopped.

[0015]

The measuring light modulation signal is not generated at the start of the measurement operation of the atomic absorption spectrophotometer, and the pseudo modulation signal from the pseudo modulation signal generating means is selected by the output selecting means. The high frequency power from the amplification means is modulated and supplied to the electrodeless discharge lamp.
When a certain time has elapsed from the start of the measurement operation of the atomic absorption spectrophotometer, a measurement light modulation signal is generated. When this measurement light modulation signal is generated, the output selection means supplies the measurement light modulation signal instead of the pseudo modulation signal to the power amplification means, and the high frequency power modulated by this measurement light modulation signal is supplied to the electrodeless discharge lamp. Is supplied to. This prevents the impedance of the excitation coil of the electrodeless discharge lamp from becoming unstable at the start of the measurement by the atomic absorption spectrophotometer, that is, when the measurement light modulation signal is generated.

Further, the command value of the output power of the power amplification means is manually set by the power value manual setting means. This makes it possible to set the electric power supplied from the power amplification means to the electrodeless discharge lamp to be gradually increased, and to avoid the impedance of the excitation coil of the electrodeless discharge lamp from becoming unstable.

Further, when the reflected wave power detected by the reflected wave power detecting means and the predetermined value are compared by the reflected wave power comparing means, the reflected wave power becomes equal to or more than the predetermined value.
The output of the modulation signal from the output selection means is stopped.
This prevents heat damage to the power amplifier due to reflected wave power.

[0018]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an overall schematic configuration diagram of an electrodeless discharge lamp lighting device for an atomic absorption photometer, which is an embodiment of the present invention. In FIG. 1, the light generated from the electrodeless discharge lamp 1 passes through the atomized sample S which is burned in the cuvette 2 into which the sample S is injected. Then, the light passing through the sample S passes through the slit 3 and reaches the diffraction grating 4,
The light is dispersed by the diffraction grating 4. The dispersed light further passes through the polarizer 5 and the chopper means 6, and reaches the photomultiplier 7. The light that has reached the photomultiplier 7 is converted into an electric signal, and this electric signal is supplied to the amplifier 8 to be amplified. Then, this amplified signal becomes a measurement signal indicating the absorbance of the sample measured at a specific wavelength.

The chopper means 6 is rotated by a motor 11. The rotation drive command signal to the motor 11 is supplied from the computer 12 via the controller 14. Commands such as measurement start and end are supplied to the computer 12 from the operation unit 13 such as a keyboard. The measurement light modulation signal generated from the chopper means 6 is transmitted to the photocoupler 9, and the transmitted modulation signal is supplied to the waveform shaping circuit 10. The signal shaped by the waveform shaping circuit 10 is supplied to the signal selection circuit 16 described later.

The modulation signal generated from the chopper means 6 is, for example, 150 if the power supply frequency is 50 Hz.
0 Hz, and if the power supply frequency is 60 Hz, 1800
It becomes Hz.

The above-mentioned cuvette 2, slit 3, diffraction grating 4, polarizer 5, chopper means 6, photomultiplier 7, amplifier 8, photocoupler 9, waveform shaping circuit 1
0, the motor 11, the computer 12, the operation unit 13, and the controller 14 constitute a detection unit 36 of the atomic absorption spectrophotometer.

Next, the electrodeless discharge lamp lighting device will be described. 27.12 generated from crystal oscillator circuit 18
A sine wave signal having an oscillation frequency of MHz is input to the attenuator 19. The output signal from this attenuator 19 is
The main power amplifier 2 of the next stage, which is amplified by the front power amplifier 20
1 is supplied. The main power amplifier 21 includes a modulation signal or pseudo modulation signal generation circuit 17 from the waveform shaping circuit 10.
The pseudo-modulated signal from is supplied via the selection circuit 16.

That is, the modulation signal d from the waveform shaping circuit 10
Is not output, the pseudo modulation signal generation circuit 1
The pseudo modulation signal from 7 is selected by the selection circuit 16 and supplied to the main power amplifier 21 as the modulation signal f.
When the modulation signal d is output from the waveform shaping circuit 10, the detection circuit 15 detects it and the switching signal e is supplied to the selection circuit 16. When the switching signal e is supplied from the detection circuit 15, the selection circuit 16 switches the selection signal from the pseudo modulation signal c to the modulation signal d, and supplies the modulation signal d to the main power amplifier 21 as the signal f.

The output g of the main power amplifier 21 is passed through the directional coupler 22 for detecting the incident wave power and the reflected wave power, and the excitation coil (of the electrodeless discharge lamp 1 with a coaxial cable having a characteristic impedance of 50Ω). 50 Ω).

Directional coupler 22 to incident / reflection detection circuit 23
The incident wave power detected via the is supplied to the power meter 27 via the amplifier 26, and the incident wave power is monitored by this power meter. The incident wave power detected by the incident / reflection detection circuit 23 is supplied to the operational amplifier 25 at one input end. A power setting command signal from the multiplexer 28 is supplied to the other input terminal of the operational amplifier 25. Then, the difference between the incident wave power and the power setting command signal is calculated by the operational amplifier 25, and the attenuation operation of the attenuator 19 is controlled based on the calculated result. That is, the output of the main power amplifier 21 is negatively feedback controlled by the amplifier 25.

The multiplexer 28 includes a D / A converter 3
The command signal a from the controller 2 and the command signal b from the D / A converter 33 are supplied as input signals.
The command signal a or b is selected according to the switching signal from 4 and supplied to the amplifier 25. That is, the command signal a is selected when the power is set manually, and the command signal b is selected when the power is set automatically.

The low-frequency clock pulse of 50 Hz generated from the oscillator 29 is supplied to the D / A converter 32 via the gate 30 and the counter 31, is D / A converted, and is supplied to the multiplexer 28 as the command signal a. It Further, an up switch 34 and a down switch 35 are connected to the gate 30.

Further, the power setting command signal output from the computer 12 is supplied to the D / A converter 33 via the controller 14, is D / A converted, and is supplied to the multiplexer 28 as a command signal b.

First, in the manual operation, the up switch 34
When is manually pushed, the low frequency clock pulse generated from the oscillator 29 is input to the count-up side of the up-down counter 31 via the gate circuit 30. The up-down counter 31 counts up the input clock pulse and supplies the parallel signal having the counted-up content to the D / A converter 32.

When the down switch 35 is continuously pressed manually, the low frequency clock pulse generated from the oscillator 29 is input to the countdown side of the up / down counter 31 via the gate circuit 30. The up / down counter 31 counts down the input clock pulse and outputs the parallel signal of the counted down D / D.
It is supplied to the A converter 32.

For switching between the manual operation and the automatic operation, for example, at the initial stage of the power supply to the electrodeless discharge lamp 1, while the feedback control is being executed, the supplied power is gradually raised by the manual operation (soft start). Then, when the electric power supplied to the electrodeless discharge lamp 1 becomes a constant value, the automatic control is performed, and the feedback control is executed so that the supplied electric power becomes a constant value.

The reflected power detected by the directional coupler 22 via the incident / reflection detection circuit 23 is supplied to one end of the analog comparator 24. A reference signal is supplied to the other end of the analog comparator 24. Then, when the reflected power becomes larger than the reference signal, the analog comparator 24 supplies a stop signal to the selection circuit 16, and the main power amplifier 2
The supply of the modulation signal (bias signal) to 1 is stopped.

This is because if the lighting fails when power is supplied to the electrodeless discharge lamp 1, fluctuations in the impedance of the excitation coil or instability of the high frequency circuit occur, the reflected wave power increases and the main power amplifier 21 generates heat. May cause damage. Therefore, in order to protect the main power amplifier 21 from heat damage, when the reflected power becomes larger than the reference value, a stop signal is supplied from the analog comparator 24 to the selection circuit 16,
The supply of the modulation signal to the main power amplifier 21 is stopped, and the output of the main power amplifier 21 is stopped. The multiplexer 28, the amplifiers 20 and 25, the attenuator 19, the oscillation circuit 18, and the entrance / exit detection circuit 23 constitute an output power control means.

FIG. 2 is a timing chart of the signals a to g in the electrodeless discharge lamp lighting device. In FIG. 2, from time t0 to time t1, the power setting command signal a or b increases in an inclined manner ((A) in FIG. 2). During this period, since the modulation signal d ((C) of FIG. 2) is not output from the waveform shaping circuit 10, the 1650 Hz pseudo modulation signal c ((B) of FIG. 2) from the pseudo modulation signal generation circuit 17 is The signal f ((E) in FIG. 2) is supplied to the main power amplifier 21 via the selection circuit 16. Therefore, the electric power g of 27.12 MHz modulated by the pseudo modulation signal c is supplied to the electrodeless discharge lamp 1 ((F) of FIG. 2).

At time t2, the waveform shaping circuit 10 outputs the modulated signal d of 1800 Hz (see FIG. 2).
(C)). At this time, the switching signal e from the detection circuit 15 becomes the “H” level ((D) of FIG. 2), and the modulation signal d is supplied to the main power amplifier 21 as the signal f.

Time points t0 to t2 when the pseudo modulation signal c is supplied
Is the preliminary lighting time of the electrodeless discharge lamp 1,
Even if the modulation signal is switched to the modulation signal d at the time point t2, the modulation signal only changes from 1650 Hz to 1800 Hz, so that the fluctuation of the impedance of the excitation coil of the electrodeless discharge lamp 1 is small and stable. This allows
At the time t2 when the measurement is started, the decrease in the brightness of the lamp due to the reflected power is avoided.

As described above, according to the embodiment of the present invention, the modulation signal d is generated from the pseudo modulation signal generation circuit 17 in the pre-measurement period in which the modulation signal d is not generated from the detection unit 36 of the atomic absorption spectrophotometer. The high frequency power supplied to the electrodeless discharge lamp 1 is modulated by the pseudo signal c. And
When the modulation signal d is generated from the detection unit 36, the electrodeless discharge lamp 1 is replaced by the modulation signal d instead of the pseudo modulation signal c.
The high frequency power supplied to is modulated. Therefore, it is possible to realize an electrodeless discharge lamp lighting device for an atomic absorption spectrophotometer, in which reflected power is suppressed even in the initial state of atomic absorption spectrophotometry, and measurement light with stable luminance can be generated.

According to the embodiment of the present invention, when the reflected wave power of the high frequency power supplied to the electrodeless discharge lamp 1 increases, the supply of the modulation signal to the main power amplifier 21 is automatically stopped. It As a result, it is possible to prevent heat damage to the main power amplifier 21 due to reflected wave power.

Further, according to the embodiment of the present invention, at the initial stage of the power supply to the electrodeless discharge lamp 1, the power supply is gradually raised by the manual operation while executing the feedback control. Thereby, the generation of reflected wave power can be suppressed and the efficiency of high frequency power can be improved.

In the above-described embodiment, the pseudo modulation signal is set to 1650 Hz which is an intermediate value between 1800 Hz and 1500 Hz. However, the frequency of the pseudo modulation signal is not limited to this, and any frequency from 1800 Hz to 1500 Hz can be used. May be In addition, the modulation signal is 1800H
Even if it is not z or 1500 Hz, the present invention is applicable, and the frequency of the pseudo modulation signal can be the same as or close to the frequency of the modulation signal.

[0041]

Since the present invention is constructed as described above, it has the following effects. The electrodeless discharge lamp (EDL), which is the light source used in the atomic absorption spectrophotometer, can maintain a constant brightness with a stable high-frequency power supply and provides a highly reliable power source. Effective in improving operability for customers.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an electrodeless lamp lighting device for an atomic absorption photometer, which is an embodiment of the present invention.

FIG. 2 is a timing chart of signals in the electrodeless discharge lamp lighting device which is the example of FIG.

[Explanation of symbols]

 1 Electrode Discharge Lamp (EDL) 2 Cuvette 3 Slit 4 Diffraction Grating 5 Polarizer 6 Chopper Means 7 Photomultipliers 8, 25, 26 Amplifier 9 Photocoupler 10 Waveform Shaping Circuit 11 Motor 12 Computer 13 Operating Unit 14 Controller 15 Signal Detection Circuit 16 Signal Selection Circuit 17 Pseudo Modulation Signal Generation Circuit 18 Crystal Oscillation Circuit 19 Attenuator 20 Front Power Amplifier 21 Main Power Amplifier 22 Directional Coupler 23 Ingress Reflection Power Detector 24 Comparator 27 Power Meter 28 Multiplexer 29 Low Frequency Oscillator 30 Gate Circuit 31 Up / down counter 32, 33 D / A converter 34 Up switch 35 Down switch 36 Detector

Claims (4)

[Claims] 1. An electrodeless discharge lamp lighting device for an atomic absorption spectrophotometer that generates a measurement light modulation signal for measuring atomic absorption photometry, and a pseudo modulation that generates a pseudo modulation signal substantially similar to the measurement light modulation signal. When the measurement light modulation signal is not generated from the signal generation means and the atomic absorption photometer, the pseudo modulation signal from the pseudo modulation signal generation means is selected and output, and the measurement light modulation signal is output from the atomic absorption photometer. When generated, the high-frequency power is modulated and amplified by the output selection means that selects and outputs the measurement light modulation signal instead of the pseudo modulation signal, and the modulation signal output from the output selection means. An electrodeless discharge lamp lighting device for an atomic absorption spectrophotometer, comprising: power amplification means for supplying high-frequency power amplified by the electrodeless discharge lamp to the electrodeless discharge lamp. 2. The electrodeless discharge lamp lighting device for an atomic absorption spectrophotometer according to claim 1, wherein a command value of the output power of the power amplification means is manually set, and a power value manual setting means capable of outputting is provided. A predetermined command value output means for outputting a predetermined output power command value of the power amplification means, or a power command value from the power value manual setting means or a power command value from the predetermined command value output means is selected. And an output power control unit for controlling the output power of the power amplification unit by issuing a command to the power amplification unit, and an electrodeless discharge lamp lighting device for an atomic absorption photometer. 3. The electrodeless discharge lamp lighting device for an atomic absorption spectrophotometer according to claim 2, wherein the output power control means includes power detection means for detecting output power of the power amplification means, and the power detection means. Comprising a means for comparing the detected power value and the power command value, based on the comparison of the power command value and the detected power value by the comparison means, to control the output power of the power amplification means A characteristic electrodeless discharge lamp lighting device for atomic absorption spectrophotometers. 4. The electrodeless discharge lamp lighting device for an atomic absorption spectrophotometer according to claim 1 or 2, and a reflected wave power detecting means for detecting reflected wave power of output power from the power amplifying means, and the reflected wave. A reflected wave power comparison means for comparing the reflected wave power detected by the power detection means with a predetermined value is further provided, and when the reflected wave power becomes a predetermined value or more, the output of the modulated signal from the output selection means. An electrodeless discharge lamp lighting device for an atomic absorption spectrophotometer, which is characterized by stopping.