JP2541059B2 - Frame atomic absorption spectrometer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flame atomic absorption spectrometer for atomizing a sample by a flame.

[0002]

2. Description of the Related Art In a flame atomic absorption spectrometer, a liquid sample (or sample solution) is atomized by a nebulizer and heated to a high temperature by a flame formed by a burner to atomize the sample.
Then, predetermined light is passed through the flame containing the atomized sample, and the absorption of light by the sample atom is measured to analyze the sample. Here, it is preferable to use a flame as hot as possible for atomizing the sample. Therefore, conventionally, an air-acetylene flame, a nitrous oxide-acetylene flame, etc. have been used depending on the analysis sample.

In order to perform accurate analysis with a flame atomic absorption spectrometer, it is necessary that the flame intensity and composition be uniform. Therefore, the pressure and flow rate of the combustion gas such as acetylene gas and the auxiliary combustion gas such as air (collectively referred to as supply gas) are constantly adjusted by the gas controller. FIG. 1 shows an example of the structure of a flame atomic absorption spectrometer including a gas controller. The gas controller 10 is a combustion gas cylinder 11
Further, the gas control circuit 15 is provided inside the auxiliary combustion gas cylinder 12 and the burner 13. In the gas controller 10, the opening / closing valves 18 and 19 and the pressure sensor 2 are provided in the combustion gas passage 16 and the auxiliary combustion gas passage 17, respectively.
0, 21 and needle valves 22, 23 are provided. Here, the needle valves 22 and 23 adjust the flow rate of each supply gas. In addition, the pressure sensor 20,
Reference numeral 21 monitors the pressure of each supply gas. When the pressure of any of the supply gas drops below a predetermined value, both on-off valves 18 and 19 are stopped (gas low pressure automatic shutoff mechanism). .

Since the flame 24 is combusted by the combustion gas such as acetylene gas and the auxiliary combustion gas such as air, the portion of the flame 24 cannot be sealed in the burner 13. Therefore, the flame 24 may disappear due to the inflow of wind from the surroundings. In this case, it is dangerous if the combustion gas and the auxiliary combustion gas continue to be ejected from the nozzle of the burner 13 as they are.
A mechanism is provided for immediately stopping the supply of both gases to the burner 13 when disappears. Since gas stop measures for extinguishing flames are a safety issue, prompt action is required. For this reason, the flame extinguishing safety mechanism is performed by a hardware sequence, not by software. That is, a flame sensor 27 that detects whether or not the flame 24 is burning is provided beside the flame 24. When the flame sensor 27 no longer detects the flame, a solenoid valve is provided by a relay provided in the gas control circuit 15. That is, the power supply to the open / close valves 18 and 19 is shut off, and the gas supply is stopped. As the flame sensor 27, a light (including infrared) sensor, a heat sensor, or the like is used.

[0005]

Due to the flame extinguishing safety mechanism, there is no danger that combustion gas or auxiliary combustion gas will continue to be ejected from the nozzle of the burner 13 even if the flame extinguishes due to wind or the like. It is unknown to those who are doing what caused the flame to go out. That is, the flame suddenly extinguishes not only when it extinguishes due to the wind from the outside as described above, but also when the above-mentioned low-pressure automatic shutoff mechanism works. For this reason, the operator must check each possible point to find the cause of the extinguished flame, and even if the cause is found, it is necessary to restart the measurement just in case. It was necessary to check if there was any inconvenience in other parts as well. The present invention was made in order to solve such a problem, and the purpose thereof is to extinguish a flame due to the influence of external wind, etc., whereby the supply of gas to the burner is stopped. Another object of the present invention is to provide a flame atomic absorption spectrometer capable of surely informing the operator of that fact.

[0006]

SUMMARY OF THE INVENTION In the present invention made to solve the above problems, in a flame atomic absorption spectrometer for atomizing a sample by a burner flame, a) whether or not the burner flame is extinguished. A flame sensor that outputs a non-combustion signal when the flame is extinguished, and b) an on-off valve that stops the gas supply to the burner and outputs a valve closing signal when a non-combustion signal is received. And c) timing detection means for receiving the non-combustion signal and the valve closing signal and outputting a notification signal when the non-combustion signal comes before the valve closing signal.

[0007]

When the flame disappears due to wind or the like, the flame sensor a detects it and outputs a non-combustion signal to the opening / closing valve and the timing detecting means. Upon receipt of this signal, the on-off valve b supplies gas to the burner and at the same time outputs a valve closing signal to the timing detection means. In this case, the timing detecting means receives the non-combustion signal first, and then receives the valve closing signal. On the other hand, when the on-off valve is closed by the gas low-pressure automatic shutoff mechanism and the flame disappears, the valve closing signal comes first and the non-combustion signal comes later. Therefore, the timing detection means c detects the front and rear of both signals, and in particular, the non-combustion signal comes first and the valve close signal comes later, so that the flame disappears and the gas The operator can be informed that the supply has been closed.

[0008]

1 to 4, the structure and operation of a flame atomic absorption spectrophotometer, which is an embodiment of the present invention, will be described. The flame atomic absorption spectrophotometer of the present embodiment also includes the gas controller 10 between the combustion gas cylinder 11, the auxiliary combustion gas cylinder 12, and the burner 13 as described above.
In the gas controller 10, the combustion gas passage 16 is provided.
And an opening / closing valve 18 in the passage 17 for the auxiliary gas,
19, pressure sensors 20, 21, and needle valve 2
2, 23 are provided. The on-off valves 18 and 19 open and close the gas supply passages 16 and 17 from the gas cylinders 11 and 12 to the burner 13, respectively.
Reference numerals 2 and 23 adjust the flow rate of each supply gas to the burner 13. The pressure sensors 20 and 21 are provided after the opening / closing valves 18 and 19.

A sensor (optical sensor or thermal sensor) 27 for detecting the flame 24 is provided beside the portion of the burner 13 where the flame 24 is formed. This flame sensor 27
4 is detected, ON when the flame 24 is not detected (that is, when the flame 24 is not burning by the burner 13)
It has a FF switch. The switch signal (ON / OFF) from the flame sensor 27 is sent to the gas control circuit 15 provided in the gas controller 10. In addition to the above, the gas control circuit 15 also includes the opening / closing valves 18, 19,
The pressure sensors 20 and 21 and the needle valves 22 and 23 are connected, and the button switch 25 for the operator to ignite the burner 13 and the button switch 2 for extinguishing the fire.
6 (both are momentary type switches) are connected. The gas control circuit 15 is also connected to the control unit (analysis control unit) 30 of the atomic absorption spectrophotometer, and sets the opening degrees of the needle valves 22 and 23 based on the flow rate signal from the analysis control unit 30. . The analysis control unit 3
A keyboard 31 and a CRT 32 are connected to 0.

Next, two safety mechanisms of the gas controller 10 will be described. First, the gas low pressure automatic shutoff mechanism will be described. Both the pressure sensors 20 and 21 are turned on when the pressure of each supply gas is higher than a predetermined value (which can be set for each supply gas),
It has a two-state switch that is turned off when it becomes a predetermined value or less, and each ON / OFF signal is sent to the gas control circuit 15. A hardware circuit for closing the on-off valve is provided inside the gas control circuit 15, and when one of the pressure sensors 20 and 21 is turned off, the on-off valve 18 is opened.
Power is shut off to both and 19. As a result, when the pressure of the supply gas of either the combustion gas or the auxiliary combustion gas drops below a predetermined value, the supply of both gases to the burner 13 is stopped.

The flame atomic absorption spectrophotometer of this embodiment is equipped with a flame extinguishing safety mechanism as another safety mechanism. This uses the flame sensor 27 as described above, and when the flame sensor 27 detects that the burner 13 does not have the flame 24 and sends an OFF signal to the gas control circuit 15, it is provided in the gas control circuit 15. The open / close valves 18 and 19 are closed by the hardware circuit provided.
FIG. 2 shows an example of a hardware circuit for closing the on-off valve using the relay 34.

However, as described above, the opening / closing valve 18 is simply
By only closing 19, it is difficult for the operator to know what causes the flame has disappeared and the valve has closed, and it is difficult to take appropriate measures to continue the measurement.
Therefore, in the gas controller 10 of the present embodiment, the open / close valves 18, 19 are turned off by extinguishing the flame 24 as described above.
A circuit (which corresponds to the above-mentioned timing detecting means) is provided in the gas control circuit 15 for notifying the operator of that fact when the valve is closed.

As shown in FIG. 3, this circuit is an AND circuit,
It is composed of discrete logic elements such as an OR circuit. The main operation of this circuit is as follows. When the flame 24 of the burner 13 disappears, the flame sensor 27 is turned off and the signal "0" is output. The output signal "0" of the flame sensor 27 is inverted by the inverter NOT2 and becomes a signal "1", which is input to the AND circuit AND3. Both open / close valves 18 and 19 are connected to the other input terminal of the AND circuit AND3, and when both open / close valves 18 and 19 are closed (both open / close valves 18 and 19 are always in the same state). A signal "0" is input to the. Therefore, the AND circuit AND3
Output becomes "1" only when there is no flame 24 in the burner 13 and both open / close valves 18 and 19 are open. The output of the AND circuit AND3 is input to the OR circuit OR2. Therefore, the above-mentioned condition (the burner 13 has no flame 24,
Moreover, when both the on-off valves 18 and 19 are open), the output of the OR circuit OR2 becomes "1".

An AND circuit AND is provided on the input side of the OR circuit OR2.
In addition to 3, another AND circuit AND2 is provided, to which a signal obtained by inverting the states of the opening / closing valves 18 and 19 by the inverter NOT3 and the output of the OR circuit OR2 are input. Therefore, the output of the AND circuit AND2 is such that both open / close valves 18 and 19 are closed, and the OR circuit OR2
Is "1" when the output of is "1".

The above operation of the circuit of FIG. 3 will be described with reference to FIG. When the flame 24 of the burner 13 is extinguished and the opening / closing valves 18 and 19 are closed by the safety mechanism (FIG. 2), as shown in the latter half of FIG. The open / close valve is turned off after a time Δt2. During this time Δt2, AND circuit AND
Since the output of 3 becomes "1", the output of the OR circuit OR2 becomes "1". Even after this time Δt2 has passed, AND
Since the output of the circuit AND2 is "1", the output "1" of the OR circuit OR2 is continued. Therefore, the OR circuit OR2
Is sent from the gas control circuit 15 to the analysis control unit 30,
By using the display on the CRT 32 or the like, the operator can be notified that the open / close valves 18 and 19 have been closed due to the extinguishment of the flame 24 of the burner 13.

On the other hand, when the open / close valves 18 and 19 are closed by the gas low-pressure automatic shut-off mechanism or the like, instead of extinguishing the flame 24, and the flame 24 disappears as a result, as shown in the latter half of FIG. 4 (b). Both on-off valves 18 and 19 are turned off first
The flame sensor 27 is turned off after a minute time Δt3. In this case, both open / close valves 1 are operated within time Δt3.
While the outputs of 8 and 19 are "0", since the flame sensor still outputs "1", the output of the inverter NOT2 is "0" and the output of the AND circuit AND3 is "0".
Further, since the AND circuit AND2 and the AND circuit AND4 both receive the output of the OR circuit OR2, the previous state "0"
To continue. Therefore, when the flame 24 disappears due to the closing of the on-off valves 18 and 19, the output of the OR circuit OR2 is "0", and the above notification signal is not sent to the analysis control unit 30. In this case, the operator has to press the fire extinguishing button 26
The same applies when you press to extinguish the fire.

When the operator presses the ignition button 25 to ignite the burner, FIG. 4A and FIG.
As shown in the first half, first the on / off valves 18 and 19 are turned on.
Next (opened), flame sensor 27 after a short time Δt1
Turns on. Therefore, the states of the on-off valves 18 and 19 and the flame sensor 27 remain in the period Δt2 for a minute time Δt1.
However, after that (that is, the open / close valves 18 and 19 are ON and the flame sensor 27 is ON), the outputs of the three AND circuits AND2, AND3, and AND4 are all "0".
Therefore, the output of the OR circuit OR2 becomes "0", and the notification signal is not sent to the analysis control unit 30.

In the circuit example described above, the timing detecting means is configured by hardware using discrete logic elements. However, such a hardware configuration has a flame 2
Even if the period Δt2 from when the extinguishing of No. 4 is detected to when the on-off valves 18 and 19 are closed is very small, it can be surely dealt with. In addition,
Instead of such a hardware configuration, the central processing unit of the analysis control unit 30 may be made to perform similar processing by software, but the CPU of the analysis control unit 30 also performs many other interrupt processing and normal processing. In this case, it is necessary to execute an interrupt with a sufficiently high priority because it must be executed. Alternatively, the gas control circuit 15 may be provided with a dedicated CPU so that it can be processed by software.

[0019]

In the flame atomic absorption spectrometer according to the present invention, when the flame is extinguished, the gas supply is immediately stopped in order to prevent the combustion gas and the auxiliary combustion gas from directly ejecting from the nozzle of the burner. It is possible to notify the operator that the flame is extinguished before the gas supply is stopped by detecting the flame extinguishing and the timing before and after the gas supply is stopped. For this reason, the operator does not need to perform unnecessary operation of checking every part of the analyzer to know the cause of the extinguishing of the flame, and take predetermined measures such as preventing external wind from flowing into the burner. After that, it will be possible to re-ignite immediately and restart the measurement.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a flame atomic absorption spectrophotometer that is an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a specific example of a mechanism for closing the on-off valve when the burner flame is extinguished in the embodiment.

FIG. 3 is a circuit diagram of a logic circuit as timing detection means provided in the gas control circuit of the embodiment.

[Fig. 4] ON / OFF of the open / close valve and O of the flame sensor when the open / close valve is closed due to the extinction of the flame (a) and when the flame is extinguished due to the close of the open / close valve (b).
The timing chart which shows the timing of N / OFF.

[Explanation of symbols]

10 ... Gas controller 11, 12 ... Gas cylinder 13 ... Burner 15 ... Gas control circuit 16, 17 ... Gas supply passage 18, 19 ... Open / close valve 20, 21 ... Pressure sensor 22, 23 ... Needle valve 24 ... Flame 27 ... Flame sensor 25 … Ignition button switch 26… Fire button switch

Claims (1)

(57) [Claims] 1. A flame atomic absorption spectrometer for atomizing a sample by a flame of a burner, comprising: a) a flame sensor which detects whether or not the flame of the burner is extinguished, and outputs a non-combustion signal when the flame is extinguished. B) When the non-combustion signal is received, the supply of gas to the burner is stopped, and the opening / closing valve that outputs the valve closing signal; and c) The non-combustion signal and the valve closing signal are received, and the non-combustion signal is A flame atomic absorption spectrometer, comprising: a timing detection unit that outputs a notification signal when the signal comes before the valve closing signal.