WO2013038584A1 - イオン化ガス検出器及びイオン化ガス検出方法 - Google Patents
イオン化ガス検出器及びイオン化ガス検出方法 Download PDFInfo
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- WO2013038584A1 WO2013038584A1 PCT/JP2012/004025 JP2012004025W WO2013038584A1 WO 2013038584 A1 WO2013038584 A1 WO 2013038584A1 JP 2012004025 W JP2012004025 W JP 2012004025W WO 2013038584 A1 WO2013038584 A1 WO 2013038584A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/62—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
- G01N27/64—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode using wave or particle radiation to ionise a gas, e.g. in an ionisation chamber
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/62—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
- G01N27/68—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode using electric discharge to ionise a gas
- G01N27/70—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode using electric discharge to ionise a gas and measuring current or voltage
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L21/00—Vacuum gauges
- G01L21/30—Vacuum gauges by making use of ionisation effects
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/62—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
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- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B17/00—Fire alarms; Alarms responsive to explosion
- G08B17/10—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means
- G08B17/11—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using an ionisation chamber for detecting smoke or gas
Definitions
- the present invention relates to an ionized gas detector and an ionized gas detection method for detecting an ionized gas to be measured.
- a charge amplifier including a capacitor is incorporated in the configuration, and charges are accumulated in the capacitor.
- the present invention relates to an ionized gas detector and an ionized gas detection method capable of specifying the concentration of a measurement target gas based on the amount of change in the amount of charge over time.
- a Photo Ionization ⁇ ⁇ Detector (hereinafter referred to as PID) is used to measure the concentration of a measurement target gas.
- the principle of PID measurement is to induce a gas to be measured in an apparatus in which a pair of application electrodes are arranged, and to irradiate the short wavelength UV to ionize the gas and capture the ions with the application electrode.
- the detected current having a correlation with the concentration is measured, and the current value is converted into the concentration, whereby the concentration of the volatile organic substance or the like is measured.
- the PID 50 includes a detection chamber 52 into which the measurement target gas is introduced and discharged, a pair of electrodes 54 provided in the detection chamber 52, and a DC voltage applied to the electrode 54.
- An application circuit 56 for applying, a UV lamp unit 58 for irradiating the measurement fluid (FL) in the detection chamber 54 with UV, a measurement circuit 60 for measuring a current flowing through the electrode 54, and a gas to be measured from the current value
- the computer 62 is configured to perform a calculation for conversion into the concentration of the liquid.
- the gas to be measured is introduced into the detection chamber 52 and discharged from the detection chamber 52 after UV irradiation by the UV lamp unit 58, but the gas to be measured is introduced into the detection chamber 52.
- the measurement target gas is ionized by UV irradiated from a UV lamp unit 58 provided on the side wall of the detection chamber 52, and the ions or electrons provided in the detection chamber 52 are applied with a direct current voltage. As a result, the current is generated in the circuit.
- this current is measured by the measurement circuit 60, and further, the calculation device 62 multiplies the current value by a coefficient for each substance (substance of the gas to be measured), thereby outputting the concentration of the gas to be measured. It is to be done. Since such a PID is sensitive to many gases to be measured, it is an effective means for measuring the gas to be measured, and since the device itself is not large, the gas to be measured can be easily measured. It is possible and very useful.
- the above-described conventional PID has a constant direction of current flow, so that when used for a long time, one of the two electrodes to which a DC voltage is applied is contaminated with one electrode such as an insulator on the surface of the metal electrode. Accumulate and ionized gas to be measured is blocked from reaching the electrode, preventing the flow of current, making it impossible to measure the correct current value and reducing the measurement sensitivity of the gas to be measured Resulting in. Further, when the metal electrode is covered with a contaminant, there has been a problem that the measurement sensitivity is lost and the function as a PID cannot be performed.
- Patent Document 1 discloses a detection electrode that detects a volatile organic compound in a measurement fluid, an application unit that applies an AC voltage or an AC current to the detection electrode, and a volatile organic compound in the measurement fluid.
- a volatile organic compound having a UV lamp for irradiating a measurement fluid with ultraviolet rays to ionize the liquid, an excitation circuit for exciting the UV lamp, and a measurement means for measuring a current or voltage flowing through the detection electrode
- An ion detector is disclosed.
- the current in the applied electrode is generated not only by the ion current but also by the detection electrode itself acting as a capacitor. Since the dielectric loss of the detection electrode is changed by the ionized volatile organic compound, the amount of charge accumulated in the capacitor is changed, and the change in the current value can be measured. Therefore, even if contamination accumulates on the detection electrode, it is said that application of alternating current to the electrode can prevent loss of measurement sensitivity. In addition, in the case of application of alternating voltage or alternating current, even if contamination accumulates in one of the two detection electrodes, the volatile organic compound ionized by the other electrode can be captured. It is said that a decrease in speed sensitivity can be prevented.
- the above-described conventional PID detects a gas to be measured by a DC voltage application method, and this generates an ionic current by providing electrodes in an ion atmosphere and applying a voltage between the electrodes. This is based on the theory that the current is detected. Usually, the ionic current flowing between the electrodes is very small. Therefore, the minute current is amplified by a DC amplifier circuit, and the ionic current is measured. It is said that the drift phenomenon of the amplifier circuit often affects the measurement of ion current.
- Patent Document 1 is a method of generating an alternating electric field between the electrodes, the ion current flowing between the electrodes can be detected even if the electrodes are insulated. Resistant to dirt and corrosion, but if the parasitic capacitance component between the electrodes is large, the current due to the parasitic capacitance between the electrodes is larger than the minute ion current, making it difficult to detect the ion current Therefore, the measurement sensitivity is lowered. In addition, since a minute ion current is detected, a device such as synchronous detection is required, and the device itself becomes large.
- the problem to be solved by the present invention is to cope with the above-mentioned problems.
- the ion current is measured for each polarity of ions, and the concentration of the gas to be measured is detected. Even if the electrode is contaminated (even if an insulated electrode is used), the detection sensitivity is not impaired, and the parasitic capacitance between the electrodes is not affected.
- An object of the present invention is to provide an ionized gas detector and an ionized gas detection method capable of eliminating the influence.
- the present invention takes the following technical means. That is, according to the first aspect of the invention, at least one pair of ion detection electrodes for detecting ions of the ionized gas to be measured and a voltage polarity for applying a predetermined voltage to the ion detection electrodes can be reversed.
- a time-dependent change in the amount of charge accumulated in the charge capacitor of the charge amplifier circuit and a charge amplifier circuit comprising a charge capacitor for accumulating charges generated by voltage application by the electrode application means;
- An ion current calculation means for calculating an ion current value of ions of the measurement target gas, and a concentration determination means for determining the concentration of the volatile organic substance from the ion current value calculated by the ion current calculation means
- the electrode applying means according to the amount of charge accumulated in the charge capacitor of the charge amplifier circuit. It is ionized gas detector; and a voltage polarity control means for inverting the.
- the invention according to claim 2 is the ionized gas detector according to claim 1, wherein the voltage polarity is reversible between the ion detection electrode and the input side of the charge amplifier circuit.
- a circuit having a voltage applying means having a voltage polarity different from that of the electrode applying means and a charge accumulating means for accumulating charges generated by application of voltage by the voltage applying means is connected, and the electrode application is performed by the voltage polarity control means.
- Voltage polarity reversing means for inverting the voltage polarity of the voltage applying means and discharging the charge accumulated in the charge accumulating means toward the ion detection electrode when the polarity of the means is reversed is provided. It is characterized by.
- the invention described in claim 3 is the ionized gas detector according to claim 1 or 2, characterized in that the ion detection electrode is covered with insulation.
- the invention according to claim 4 is an ion detection step of detecting ions of the ionized gas to be measured by an ion detection electrode to which a predetermined voltage is applied, and ions detected by the ion detection electrode.
- the polarity of the voltage applied to the ion detection electrode is determined according to the concentration determination step for determining the concentration of the gas to be measured from the calculated ion current value and the amount of charge accumulated in the charge accumulation step.
- a voltage polarity reversing step for reversing the ionized gas.
- a fifth aspect of the present invention is the ionized gas detection method according to the fourth aspect, wherein the charge generated by applying a voltage different from the polarity of the voltage applied to the ion detection electrode is preliminarily accumulated.
- the charge accumulated in the preliminary charge accumulation step is directed toward the ion detection electrode.
- a charge discharging step of discharging is the charge generated by applying a voltage different from the polarity of the voltage applied to the ion detection electrode.
- the influence of a DC drift such as a temperature drift is less than that of the detection by the DC application method, and even if the electrode is contaminated (insulating electrode is removed). Even if it is used), high detection sensitivity can be obtained and the polarity of the voltage can be reversed, so that positive ions and negative ions can be measured continuously. Further, it is possible to eliminate the influence of the parasitic capacitance between the electrodes.
- FIG. 1 It is the schematic diagram which showed an example at the time of insulating the surface of an ion detection electrode. It is the figure which showed an example of the equivalent circuit at the time of expressing the capacity
- FIG. 6 is an example showing the relationship between charge transfer caused by voltage polarity inversion and output response when a compensation circuit is connected, (a) is a diagram showing an example of the circuit configuration of a detector, and (b) is an output. It is the graph which showed an example of the relationship of a response. It is the schematic diagram which showed an example of the structure of the conventional PID. 4 is a graph showing experimental results obtained by measuring a change in an output voltage value from an operational amplifier with an oscilloscope in the first embodiment of the ionized gas detector according to the present invention. It is the graph which showed the experimental result which measured the change of the output voltage value from an operational amplifier with the oscilloscope in 2nd Embodiment of the ionization gas detector which concerns on this invention.
- FIG. 1 is a diagram showing an example of the configuration of a detector in the first embodiment of the ionized gas detector according to the present invention, where (a) is a diagram showing an example of the circuit configuration of the detector, and (b). Represents the relationship between the voltage between the electrodes and the output of the charge amplifier circuit.
- 2 is a diagram showing an example of the first embodiment of the ionized gas detector according to the present invention.
- FIG. 2A is an example of the circuit configuration of the detector when the voltage polarity in FIG. 1 is reversed.
- (B) shows the relationship between the voltage between electrodes and the output of the charge amplifier circuit before and after inversion of the voltage polarity.
- 10 is an ionized gas detector
- 12 is an ion detection electrode
- 14 is an electrode application means
- 16 is a charge amplifier circuit
- 18 is a charging capacitor
- 20 is an operational amplifier
- 22 is an ion current calculation means
- 24 is a concentration determination means
- Reference numeral 26 denotes voltage polarity control means.
- an ionization gas detector 10 has an ion detection electrode 12 that detects ions of an ionized measurement target gas flowing in, and a voltage with respect to the ion detection electrode 12.
- a charge amplifier circuit 16 is provided.
- the ion detection electrode 12 may be an insulating coating.
- the voltage polarity control means 26 for inverting the voltage polarity of the electrode application means 14 according to the charge amount charged in the charge capacitor 18, and the temporal change in the charge amount charged in the charge capacitor 18 (operational amplifier) 20), an ion current calculation means 22 for calculating an ion current value from the output voltage value and a concentration determination means 24 for determining the concentration of the gas to be measured from the ion current value.
- ionized ions of the measurement target gas are captured by the ion detection electrode 12 to which a predetermined voltage is applied by the electrode application unit 14. Then, when ions are captured by the ion detection electrode 12, a current is generated in the ion detection electrode 12, whereby the charge capacitor 18 of the charge amplifier circuit 16 is charged.
- the operational amplifier 20 is preferably a CMOS operational amplifier having a small bias current (about several hundred fA).
- the charging capacitor 18 If a capacitor having a small capacitance is used as the charging capacitor 18, a large output voltage can be obtained with a small ion current.
- the interelectrode voltage V is 100 (V), and the resistance R due to ions between the electrodes is reduced.
- a capacitor having 10 G ( ⁇ ) and a charging capacitor capacitance C of 100 (pF) is used, an output voltage value can be obtained as shown in the following equation.
- the output voltage value changes with the passage of time, 0.1 V after 1 msec from the start of charge charging, and 0.2 V after 2 msec. Because of such a configuration, the ion current can be detected by a simple method.
- the present invention adopts a configuration in which the polarity of the voltage applied to the ion detection electrode 12 is reversed when a certain amount of charge is charged in the charging capacitor 18.
- the ion current between the ion detection electrodes 12 flows in the opposite direction, and the charge of the charging capacitor 18 can be discharged.
- the voltage polarity control means 26 grasps the amount of charge charged in the charging capacitor 18 by measuring the value of the output voltage of the operational amplifier 20, and when the predetermined amount of charge is reached, the electrode application means 14 The voltage polarity is controlled to be inverted.
- the voltage polarity of the electrode applying means 14 is reversed by the voltage polarity control means 26, as shown in FIG. 2A, the charges accumulated from the charging capacitor 18 are ionized gas (plus ions) between the electrodes. It will be discharged by. As shown in FIG. 2B, the output voltage value of the operational amplifier 20 gradually increases toward the output level 0 after the voltage polarity is inverted.
- the collection of positive ions and negative ions can be controlled by the electric field between the ion detection electrodes 12 (positive ions). And negative ions can be measured continuously). Further, by measuring the change in the charging speed and the discharging speed of the charging capacitor 18, it is possible to measure the difference in the movement speed of the positive ions and negative ions of the ionized gas to be measured. is there.
- the ion current calculation means 22 calculates the current value of the ion current from the temporal change amount of the output voltage value of the operational amplifier 20, that is, the temporal change amount of the charge charged in the charging capacitor 18. Specifically, it is based on the following formula.
- the offset voltage may change due to temperature drift or the like, and this offset voltage directly affects the measured value.
- the output voltages Vout1 and Vout2 are affected by the drift.
- the concentration determination unit 24 determines the concentration of the measurement target gas from the current value of the ion current calculated by the ion current calculation unit 22. Note that the concentration determination by the concentration determination unit 24 is performed, for example, by multiplying the current value of the ionic current by a predetermined coefficient.
- the relationship between the electric field between the ion detection electrodes 12 and the ion current can be represented as an example in FIG. 5, and the ion current is represented by the following equation.
- FIG. 6 shows a schematic diagram when the surface of the ion detection electrode 12 is insulated as an example.
- electrode area (A): 10 mm ⁇ 10 mm Insulating film: polyimide (relative permittivity ⁇ r 4) Insulating film thickness (d): 10 ⁇ m Resistance value by ion (R): 10G ⁇ Electrode voltage (E): 100V
- the capacitance C, time constant ⁇ , and initial current value i due to the insulating electrode are given by the following equations.
- Equation 7 the rate of change between the direct current and the current due to the insulating film is as shown in equation (9).
- the accuracy of the ionized gas detector is about ⁇ 10%, it can be seen that the influence of the insulating electrode is very small as described above.
- the time constant due to the insulating electrode is expressed by Equation 10, and the larger the time constant, the smaller the difference from the DC application method.
- R depends on the ionized gas concentration
- C is determined by the thickness of the insulating film and the relative dielectric constant of the insulating film.
- the insulating film is made of polyimide and has a thickness of 10 ⁇ m, even when the insulating film is thick, it is possible to accurately measure the ionized gas by using a material having a high dielectric constant.
- the output voltage value of the operational amplifier 20 is increased or decreased due to the reversal of the voltage polarity.
- the ion detector in the present embodiment is used, even if an insulating electrode is used as the ion detection electrode, it is possible to detect the ionized gas with the same accuracy as the detection of the ionized gas by the DC application method due to a transient phenomenon. I understand.
- FIG. 4 is a diagram showing an example of the configuration of a detector in the second embodiment of the ionized gas detector according to the present invention, where (a) is a diagram showing an example of the circuit configuration of the detector, and (b). Represents the relationship between the voltage between the electrodes and the output of the charge amplifier circuit.
- the reference numerals are the same as those in FIGS. 1 and 2 except that 28 is a voltage applying unit, 30 is a charge storage unit, 32 is a compensation circuit, and 34 is a voltage polarity inversion unit.
- the ionization gas detector 10 is applied with a voltage to the ion detection electrode 12 that detects the ions of the ionized gas to be measured and the ion detection electrode 12.
- a charge amplifier circuit having an electrode application means 14 configured to be capable of reversing the voltage polarity, and further comprising a charge capacitor 18 and an operational amplifier 20 for charging a charge generated by applying a voltage to the ion detection electrode 12. 16 is provided.
- the ion detection electrode 12 may be an insulating coating.
- the voltage polarity control means 26 for inverting the voltage polarity of the electrode applying means 14 according to the charge amount charged in the charge capacitor 18, and the temporal change in the charge amount charged in the charge capacitor 18,
- An ion current calculation means 22 for calculating the value of the ion current and a concentration determination means 24 for determining the concentration of the gas to be measured from the value of the ion current are provided.
- a voltage application unit 28 having a voltage polarity different from the electrode application unit 14 configured to be able to reverse the voltage polarity, and a voltage by the voltage application unit 28.
- a compensation circuit 32 having a charge storage means 30 for storing charges generated by the application of the voltage, and at the timing of the polarity inversion control of the electrode application means 14 by the voltage polarity control means 26.
- Voltage polarity reversing means 34 for reversing the voltage polarity is provided.
- the voltage polarity control means 26 Inverts the voltage polarity of the electrode application means 14. At this time, the charge capacitor 18 and the ion detection electrode are reversed. Since there is no element such as a resistor between the capacitor 12 and the charge 12, the charge is suddenly moved from the charging capacitor 18 to the ion detection electrode 12 side. Then, since the value of the output voltage of the operational amplifier 20 changes suddenly, an error occurs in the calculation of the ion current value (see FIG. 8).
- the sudden change in the value of the output voltage is caused when the voltage applied to the ion detection electrode 12 is increased or the parasitic capacitance between the ion detection electrodes 12 is large (for example, the distance between the electrodes is decreased and the electrodes themselves are increased).
- the voltage applied to the ion detection electrode 12 it is necessary to increase the voltage applied to the ion detection electrode 12 and reduce the distance between the ion detection electrodes 12. It is important to suppress sudden changes in the output voltage value.
- the charge is compensated by the charge storage means 30 (capacitor) of the compensation circuit 32 connected in parallel with the ion detection electrode 12 so that the charge of the charge capacitor 18 does not fluctuate rapidly.
- the voltage applying unit 28 applies a voltage having a voltage polarity different from that of the electrode applying unit 14 to the charge accumulating unit 30 to charge the charge accumulating unit 30 in advance, and the voltage polarity controlling unit 26
- the voltage polarity reversing unit 34 recognizes that the voltage polarity of the applying unit 14 has been reversed, the voltage polarity reversing unit 34 reverses the voltage polarity of the voltage applying unit 28.
- the charge charged in the charge accumulating means 30 moves toward the ion detection electrode 12, and it is possible to suppress rapid fluctuation of the charge from the charge capacitor 18 to the ion detection electrode 12. It becomes.
- the voltage of the voltage applying means 28 is adjusted to a value suitable for suppressing rapid fluctuations in the charge from the charging capacitor 18 to the ion detection electrode 12 or is automatically adjusted, The current calculation accuracy can be further improved.
- ionized ions of the measurement target gas are captured by the ion detection electrode 12 to which a predetermined voltage is applied by the electrode application unit 14. Then, when ions are captured by the ion detection electrode 12, a current is generated in the ion detection electrode 12, whereby charges are charged in the charging capacitor 18 of the charge amplifier circuit 16.
- the operational amplifier 20 is preferably a CMOS operational amplifier having a small bias current (about several hundred fA). Further, if a capacitor having a small capacitance is used as the charging capacitor 18, a large output voltage can be obtained with a small ion current.
- the present invention adopts a configuration in which the polarity of the voltage applied to the ion detection electrode 12 is reversed when a certain amount of charge is charged in the charging capacitor 18.
- the ion current between the ion detection electrodes 12 flows in the opposite direction, and the charge of the charging capacitor 18 can be discharged.
- the voltage polarity control means 26 grasps the amount of charge charged in the charging capacitor 18 by measuring the value of the output voltage of the operational amplifier 20, and when the predetermined amount of charge is reached, the electrode application means 14 The voltage polarity is controlled to be inverted.
- the voltage polarity of the electrode applying means 14 is reversed by the voltage polarity control means 26, the charges accumulated from the charging capacitor 18 are discharged by ionized gas (plus ions) between the electrodes.
- the output voltage value of the operational amplifier 20 gradually increases toward the output level 0 when the voltage polarity is inverted.
- the collection of positive ions and negative ions can be controlled by the electric field between the ion detection electrodes 12.
- the change in the speed at which the charging capacitor 18 is charged and the speed at which it is discharged it is possible to measure the difference in the movement speed of positive ions and negative ions.
- the voltage polarity reversing means 34 reverses the voltage polarity of the voltage applying means 28 at the timing when the voltage polarity controlling means 26 reverses the voltage polarity of the electrode applying means 14.
- the voltage polarity control means 26 can stably obtain the value of the output voltage of the operational amplifier 20 even when the voltage polarity of the electrode application means 14 is inverted (between the electrodes). Can cancel the effects of parasitic capacitance). Note that the voltage of the voltage applying means 28 is adjusted to a value suitable for suppressing rapid fluctuations in the charge from the charging capacitor 18 to the ion detection electrode 12 or is automatically adjusted, The current calculation accuracy can be further improved.
- Example 2 Here, in the first embodiment and the second embodiment of the ionized gas detector according to the present invention, an experiment was performed to measure a change in the output voltage value from the operational amplifier 20 with an oscilloscope. The experimental results are shown as graphs in FIG. 11 (first embodiment) and FIG. 12 (second embodiment).
- the voltage value applied to the ion detection electrode 12 was ⁇ 35 V, and the voltage polarity was inverted three times. As shown in FIG. 11, it was found that when the voltage polarity was inverted in the first embodiment, the charge was moved rapidly and a gap of about 0.9 V was generated. This gap causes an error in the calculation of the ion current value.
- the voltage value applied to the ion detection electrode 12 was ⁇ 35 V, and the reversal of the voltage polarity was performed twice.
- the voltage value of the voltage applying means 28 is configured to be automatically adjusted to an appropriate value so as to prevent the charge from moving abruptly (so as not to cause a gap). .
- FIG. 12 in the second embodiment, it has been found that even if the polarity of the voltage is reversed, it is possible to suppress the rapid movement of charges.
- the ionized gas detector and the ionized gas detection method according to the present invention it is possible to detect ionized gas with high accuracy with a simple configuration and a small apparatus, and to influence the temperature drift or the like as compared with the DC application method. Even if the ion detection electrode is contaminated, it is possible to detect with high accuracy in the same manner. Therefore, it is useful for detection of ionized gas that needs to be performed in various situations and environments.
Abstract
Description
即ち、請求項1記載の発明は、イオン化された被測定対象ガスのイオンを検出する少なくとも1対のイオン検出電極と、前記イオン検出電極に対して所定の電圧を印加する電圧極性が反転可能に構成された電極印加手段と、前記電極印加手段による電圧の印加により生じる電荷を蓄積するチャージ用コンデンサを備えるチャージアンプ回路と、前記チャージアンプ回路のチャージ用コンデンサに蓄積される電荷量の時間的変化に基づいて、前記被測定対象ガスのイオンのイオン電流値を算出するイオン電流算出手段と、前記イオン電流算出手段により算出されたイオン電流値から、前記揮発性有機物の濃度を判定する濃度判定手段と、前記チャージアンプ回路のチャージ用コンデンサに蓄積されている電荷量に応じて、前記電極印加手段の極性を反転させる電圧極性制御手段とを有することを特徴とするイオン化ガス検出器である。
図1は、本発明に係るイオン化ガス検出器の第1の実施形態における検出器の構成の一例を示した図で、(a)は検出器の回路構成の一例を表した図、(b)は電極間電圧と、チャージアンプ回路の出力との関係を表している。さらに、図2は、本発明に係るイオン化ガス検出器の第1の実施形態の一例を示した図で、(a)は図1における電圧極性を反転させた際の検出器の回路構成の一例を表した図で、(b)は電圧極性の反転前後における、電極間電圧と、チャージアンプ回路の出力との関係を表している。また、10はイオン化ガス検出器、12はイオン検出電極、14は電極印加手段、16はチャージアンプ回路、18はチャージ用コンデンサ、20はオペアンプ、22はイオン電流算出手段、24は濃度判定手段、26は電圧極性制御手段を示している。
電極面積(A):10mm×10mm
絶縁膜:ポリイミド(比誘電率εr=4)
絶縁膜の厚み(d):10μm
イオンによる抵抗値(R):10GΩ
電極電圧(E):100V
絶縁電極による容量C、時定数τ及び初期電流値iは、次式のものとなる。
ここで、本発明に係るイオン化ガス検出器の第1の実施形態において、下記測定条件にてイオン化ガスの検出実験を行った。実験結果は、図3に一例として示す。
イオン化ガス:トルエン10ppm
印加電圧:20V
コンデンサ容量:100pF
イオン検出電極:ポリイミドによる絶縁電極
図4は、本発明に係るイオン化ガス検出器の第2の実施形態における検出器の構成の一例を示した図で、(a)は検出器の回路構成の一例を表した図、(b)は電極間電圧と、チャージアンプ回路の出力との関係を表している。なお、符号については、28が電圧印加手段、30が電荷蓄積手段、32が補償用回路、34が電圧極性反転手段である以外は、図1及び図2と同様である。
ここで、本発明に係るイオン化ガス検出器の第1の実施形態と、第2の実施形態において、オペアンプ20からの出力電圧値の変化をオシロスコープにより測定する実験を行った。実験結果は、図11(第1の実施形態)、図12(第2の実施形態)にグラフとして示している。
12 イオン検出電極
14 電極印加手段
16 チャージアンプ回路
18 チャージ用コンデンサ
20 オペアンプ
22 イオン電流算出手段
24 濃度判定手段
26 電圧極性制御手段
28 電圧印加手段
30 電荷蓄積手段
32 補償用回路
34 電圧極性反転手段
Claims (5)
- イオン化された被測定対象ガスのイオンを検出する少なくとも1対のイオン検出電極と、
前記イオン検出電極に対して所定の電圧を印加する電圧極性が反転可能に構成された電極印加手段と、
前記電極印加手段による電圧の印加により生じる電荷を蓄積するチャージ用コンデンサを備えるチャージアンプ回路と、
前記チャージアンプ回路のチャージ用コンデンサに蓄積される電荷量の時間的変化に基づいて、前記被測定対象ガスのイオンのイオン電流値を算出するイオン電流算出手段と、
前記イオン電流算出手段により算出されたイオン電流値から、前記揮発性有機物の濃度を判定する濃度判定手段と、
前記チャージアンプ回路のチャージ用コンデンサに蓄積されている電荷量に応じて、前記電極印加手段の極性を反転させる電圧極性制御手段と、
を有することを特徴とするイオン化ガス検出器。 - 前記イオン検出電極と、前記チャージアンプ回路の入力側との間に、
電圧極性が反転可能に構成された前記電極印加手段と電圧極性が異なる電圧印加手段と、
前記電圧印加手段による電圧の印加により生じる電荷を蓄積する電荷蓄積手段と、
を有する回路が接続され、且つ、
前記電圧極性制御手段により前記電極印加手段の極性が反転された際に、前記電圧印加手段の電圧極性を反転させ、前記電荷蓄積手段に蓄積された電荷を前記イオン検出電極に向けて放電させる電圧極性反転手段が設けられていることを特徴とする請求項1記載のイオン化ガス検出器。 - 前記イオン検出電極は絶縁被覆されていることを特徴とする請求項1又は2記載のイオン化ガス検出器。
- イオン化された被測定対象ガスのイオンを所定電圧が印加されたイオン検出用の電極により検出するイオン検出工程と、
前記イオン検出用の電極に検出されたイオンにより生じる電荷を蓄積する電荷蓄積工程と、
前記蓄積される電荷量の時間的変化に基づいて前記被測定対象ガスのイオン電流値を算出するイオン電流値算出工程と、
前記イオン電流値算出工程により算出されるイオン電流値から、前記被測定対象ガスの濃度を判定する濃度判定工程と、
前記電荷蓄積工程により蓄積される電荷量に応じて、前記イオン検出用の電極に印加する電圧の極性を反転させる電圧極性反転工程と、
を含むことを特徴とするイオン化ガス検出方法。 - 前記イオン検出用の電極に印加する電圧の極性と異なる電圧を印加することにより生じる電荷を予め蓄積する予備電荷蓄積工程と、
前記電圧極性反転工程により、前記イオン検出用の電極に印加する電圧の極性が反転された際に、前記予備電荷蓄積工程において蓄積した電荷を前記イオン検出用の電極に向けて放電させる電荷放電工程と、
を含むことを特徴とする請求項4記載のイオン化ガス検出方法。
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CN116824789A (zh) * | 2023-03-11 | 2023-09-29 | 中国船舶重工集团公司第七0三研究所 | 一种电容式粒子分析型感烟探测器及其粒子浓度检测方法 |
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