JP3084961B2 - Halogen gas leak detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a halogen gas leak detector and, more particularly, to a halogen gas leak detector which has a long life by suppressing the consumption of a cation-emitting alkali metal.

[0002]

2. Description of the Related Art FIG. 3 shows a general configuration example of a conventionally known halogen gas leak detector. FIG.
In the above, 20 is a sensor (cation release type), 21 is a manifold, 22 is a suction pump, 24 is a flow rate decrease detector, 25 is a filter, 26 is a calculation unit, 27 is a display unit,
28 is a probe and 30 is a storage case.

In the above configuration, when the suction pump 22 is driven, the halogen gas to be measured is taken into the manifold 21 via the probe 28, and circulates through a loop composed of the filter 25 and the flow rate decrease detector 24. Then, a part of the electric signal is sent to the sensor 20 and converted into an electric signal corresponding to the concentration. The electric signal is sent to the calculating section 26 to perform a predetermined calculation, and the gas concentration is displayed on the display section 27.

FIG. 4 is a configuration diagram showing details of a main part of a conventional example of the sensor 20. As shown in FIG. In the figure, reference numeral 1 denotes a first electrode which also serves as a filament, is formed in a coil shape having a space inside, and a first power supply 2 is connected to both ends thereof.
Reference numeral 3 denotes a second electrode formed by applying a heat-resistant inorganic insulator 6 containing an alkali metal element to a platinum rod 5, for example.
Are arranged near the center of the coil in a non-contact state with the coil. Reference numeral 4 denotes a second power supply, the negative side of which is grounded and the positive side of which is connected to one end of the second electrode 3 via a resistor Rs. The filament diameter of the first electrode 1 is, for example, 40 μm, the coil diameter is 250 μm, and the diameter of the platinum rod 5 is 5 μm.
0 μm, and the diameter of the inorganic insulator 6 is about 150 μm.
Next, the operation of the cation emission type sensor will be described. In general, alkali metals are in the group having the lowest ionization potential in the periodic table. On the other hand, since the halogen element has a very strong electron affinity, when these two come close to each other, positive and negative univalent ions are easily generated.

The first electrode 1 is a heated anode for decomposing CFC gas, and the second electrode 3 functions as a cathode (ion collector) in which a platinum tube is filled with an alkali metal for promoting cation release. I do. And the first electrode 1
, A central portion is heated to about 800 ° C., and a DC voltage of several tens of volts is applied between the first electrode 1 and the second electrode 3.
Now, when a halogen compound such as chlorofluorocarbon gas is introduced into the sensor, the chlorofluorocarbon gas is firstly decomposed at a high temperature to be decomposed into a halogen element (molecule) and another halogen compound.

On the other hand, a part of the alkali metal attached to the second electrode 3 evaporates at a high temperature and exists as an alkali metal vapor. When the above-mentioned chlorofluorocarbon gas is mixed therein, positive and negative monovalent ions are generated by the halogen element taking away electrons from the alkali metal. These ions move due to the high electric field applied to the space, reach the positive and negative electrodes, and generate an output current. Therefore, by measuring the output current, it is possible to measure the amount of CFC gas leakage.

[0007]

By the way, in the above-mentioned conventional apparatus, a dry battery is used as a power source, and a voltage of about 2 V is applied to the first electrode and a voltage of about 20 V is applied to the second electrode. Since the sensor is small, the amount of the alkali metal element held in the inorganic heat-resistant material is very small. The alkali metal is consumed by the reaction with the halogenated hydrocarbon. Furthermore, when the concentration of the halogenated hydrocarbon is increased at a constant voltage, the output current increases and the consumption of the alkali metal increases, so that the life of the sensor is extended. There was a problem that it became extremely short. SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a detector having a longer life of a sensor.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a coil-shaped first electrode serving also as a heating filament, and an alkali metal disposed in the coil-shaped first electrode. A second electrode coated with a heat-resistant inorganic insulator containing an element, a first power supply for applying a voltage to the first electrode, a second power supply for applying a voltage to the second electrode, A resistor connected in series between the second electrodes and a deviation amplifier for inputting a current flowing through the first electrode and a predetermined set current and outputting a deviation thereof, and based on an output of the deviation amplifier, 2 Halogen controlling voltage of power supply
A gas leak detector, wherein the voltage of the second power supply is a synchronous signal.
Signal and the output of this synchronization signal generator.
Pulsing based on the output of the deviation amplifier detected
It is a characteristic that the pulse voltage is applied .

[0009]

[Action] First, in the absence of halogenated hydrocarbons,
A predetermined voltage is applied to the second electrode, and a current flowing through a resistor connected in series to the first electrode and the second electrode is measured (a small amount of current flows even without halogen gas). The current is used as a setting input of the deviation amplifier. Next, when the transistor is placed in a halogenated hydrocarbon atmosphere, the current flowing through the resistor Rs tends to increase, but the deviation amplifier outputs a signal to decrease the voltage of the second power supply and controls the deviation to be zero.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, referring to FIG.
The principle configuration of the gas leak detector will be described. In the figure, the same elements as those in FIG. 4 are denoted by the same reference numerals, and duplicate description is omitted. In this figure, a resistor Rs ′ is connected between the point where the first power supply 2 and the first electrode 1 are connected and the ground. One end of the connected first electrode 1 is connected to one terminal (non-inverting terminal) of the deviation amplifier 10. The output of the deviation amplifier 10 is input to the second power supply 4 '. Here, as the second power source 4 ′, one having a variable voltage is used, and the dimensions of each electrode are the same as those shown in FIG.

In the above configuration, when a voltage of, for example, about 2 V is applied to the first electrode from the first power supply 2 in the absence of a halogenated hydrocarbon, the first electrode 1 is heated to about 800.degree. At the same time, a voltage of about 20 V is applied to the second electrode 3 from the second power supply 4 '. In this case, for example, 0.
A current of about 2 μA flows. This 0.2 μA current is input to the inverting terminal of the deviation amplifier 10 as a setting input.
In this state, since there is no deviation in the deviation amplifier 10, the voltage of the second power supply 4 'is kept constant.

Next, when the sensor is placed in a halogenated hydrocarbon atmosphere, an output current is generated between the first and second electrodes 1 and 3 according to the principle described above, and the current flowing through the resistor Rs' increases. This current is input to the inverting terminal of the deviation amplifier 10, and the deviation amplifier 10 outputs a signal corresponding to the deviation from the setting input. This signal is input to the second power supply 4 'and changes (decreases) the voltage of the second power supply 4' so as to make the deviation zero. This change in the power supply voltage is related to the concentration of the halogenated hydrocarbon. According to experiments by the present inventors, the life of the electrode in the conventional example was about 15 hours, but it was possible to extend it to about 30 hours with the device having this configuration .

[0013] Figure 2 is a basic structure in which indicating the actual施例of the present invention is similar to that shown in FIG. Here, the voltage of the second power supply 4 'shown in FIG. 2 is converted into a pulse voltage by the synchronization signal generator 20, and the synchronization signal from the synchronization signal generator 20 is superimposed on the output of the deviation amplifier 10 to synchronize. The signal is input to the detector 21 and synchronous detection is performed. The low-pass filter 22 cuts high-frequency noise generated at the time of synchronous detection and inputs the cut-off high-frequency noise to the second power supply 4 ′. By adding the synchronous detection method in this way, the S / N can be improved, the current can be reduced correspondingly, and the current flowing time is reduced by half, so that the life of the first electrode is reduced. Can be greatly extended.

[0014]

According to the present invention, the cation emission type detector is driven at a constant current as described in detail with the above embodiments, so that the consumption of alkali metal can be reduced. A halogen gas leak detector having a longer life can be realized.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram showing a halogen gas leak detector of the present invention.

FIG. 2 is a diagram showing a principle of a halogen gas leak detector according to the present invention .
FIG .

FIG. 3 is a diagram showing a general configuration example of a halogen gas leak detector.

FIG. 4 is a diagram showing a configuration of a conventional detector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st electrode 2 1st power supply 3 2nd electrode 4, 4 '2nd power supply 5 Platinum 6 Inorganic insulator 10 Deviation amplifier

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01N 27/62-27/70 G01M 3/00-3/40

Claims (1)

(57) [Claims] A coil-shaped first electrode serving also as a heating filament, and disposed in the coil-shaped first electrode;
A second electrode coated with a heat-resistant inorganic insulator containing an alkali metal element; a first power supply for applying a voltage to the first electrode; a second power supply for applying a voltage to the second electrode; A resistor connected in series between the first and second electrodes, and a deviation amplifier for inputting a current flowing through the first electrode and a predetermined set current and outputting a deviation thereof, based on an output of the deviation amplifier. Halogen for controlling the voltage of the second power supply
A gas leak detector, wherein the voltage of the second power supply is a synchronous signal.
Signal and the output of this synchronization signal generator.
Pulsing based on the output of the deviation amplifier detected
A halogen gas leak detector characterized in that a pulse voltage is applied .