JPH029311B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a measuring device that makes it possible to easily and accurately measure the current density of positive and negative ions in an electric field where ions of both positive and negative polarities exist. be.

In another invention, "Bipolar ion current probe device" (Japanese Patent Application No. 55-066229), the present inventor developed a "Bipolar ion current probe device" which is a measuring device for measuring the positive and negative ion current density in an electric field where bipolar ions exist. We first proposed a bipolar ion current probe device. However, in practical use, it is necessary to match the probe potential to the space potential at the measurement point (hereinafter referred to as equilibrium potential), or to set a quasi-equilibrium potential at which the current at the center electrode for detecting the equilibrium point becomes zero. In each case, it was impossible to obtain a measured value without going through an extremely complicated and difficult detection operation.

The object of the present invention is to eliminate such drawbacks and provide a new "bipolar ion current probe device" which is extremely easy to operate.

However, the present invention has achieved this purpose by arranging the three electrodes symmetrically with respect to the plane of symmetry of the probe of the above-mentioned invention.
This is achieved by fundamentally changing the configuration and arranging the three electrodes asymmetrically with respect to the plane of symmetry of the probe as described below.

Before describing the present invention in detail, the above-mentioned prior invention (hereinafter referred to as symmetrical probe) will first be outlined.
Figure 1 shows the basic configuration of the symmetrical probe, in which a small virtual surface F (spherical or cylindrical in this figure) having a symmetrical shape on both sides of the plane of symmetry C ₁ - _{C 2} is used as the probe surface. , a long center electrode C with a small width is placed on the intersection line S of the F plane and the C ₁ - C ₂ plane.
(ring-shaped for spherical probes, strip-shaped for cylindrical probes) is insulated, and on the F plane on both sides, S
Measurement electrodes A and B (approximately hemispherical for a spherical probe, cylindrical (in the case of a type probe, it has an approximately semi-cylindrical shape) and is insulated to form one symmetrical three-electrode probe. Now, insert the C ₁ - C ₂ plane perpendicularly to the electric field at a point P in the electric field where the bipolar ions to be measured exist, and change the potentials of the three electrodes A, B, and C to the original potential at point P ( (equilibrium potential), _the electric field _becomes electric field lines 1,
As shown by 1', a mutually symmetrical distribution is exhibited. At this time, the A electrode absorbs only positive ion current, and the B electrode absorbs only negative ion current, and the currents I ₊ and I _-
is the current density due to only positive ions at point P
Theoretically, J ₊ has the following relationship with the current density J _- due to negative ions only.

I ₊ =kJ ₊ ...(1) I _- =kJ _- ...(2) However, k is a geometric coefficient determined by the shape of the probe and the dimensions of electrodes A, B, and C. In the case of a spherical probe, k=3πa ² (d/2a) ² , and in the case of a cylindrical probe, k=4al(d/2a). However, a=probe radius, d=width of the C electrode, l=axial length of the electrode in the cylindrical electrode. Therefore, theoretically, if the three electrodes A, B, and C of the probe are connected to a common external variable voltage line and the potential is made to match the equilibrium potential, the currents I ₊ and I from the A and B electrodes By measuring _- , you should be able to immediately obtain the values of J ₊ and J _- . However, as already mentioned, the problem with the paired box probe lies in the difficulty in determining this equilibrium potential. In other words, (1) The current I _c of electrode C will not be zero even under an equilibrium potential as long as there is a difference between J ₊ and J _- , but there is a method of approximating the equilibrium potential by setting the potential of I _c = 0 as a quasi-equilibrium potential. Then, the current values I ₊ ′, I ₋ ′ from the A electrode and B electrode will deviate considerably from the equilibrium potential values I ₊ , I ₋ ,
J ₊ , J _- obtained by substituting I + _′ , I _- ′ into the above equations (1) and (2)
The value of has a large error. If the width of the C electrode is reduced in an attempt to prevent this, I _c becomes extremely small, and its zero detection becomes extremely inaccurate.
This also causes large errors in J ₊ and J _- .

(2) If we take the ratio of the current values of the A and B electrodes determined at the above quasi-equilibrium potential, it is correct as a function.
Although correction coefficients for determining I ₊ and I _- can be calculated theoretically, the calculation is extremely complicated.

(3) It is possible to graphically determine the equilibrium potential and I ₊ and I _c at that potential by measuring the A, B, and C currents while changing the probe potential and plotting them on a graph. The method is extremely time consuming and the results obtained are inaccurate.

In the end, no matter which method is used, in reality, as long as a symmetrical probe is used, there is no means to accurately and quickly determine the equilibrium point, and this was the biggest drawback in its use. The present invention solves this drawback by making the arrangement of electrodes A, B, and C asymmetric, as described below.

FIG. 2 is a diagram showing the basic configuration of the present invention (hereinafter referred to as an asymmetric probe). C ₁ - C ₂ is a symmetry plane, and the probe surface has a small virtual surface F (spherical or cylindrical in this figure) with a symmetrical shape on both sides, as in the case of the symmetrical probe in Fig. 1. It is. However, in the asymmetrical probe of the present invention, there is no center C electrode, and the electrode B is insulated so as to cover the entire lower half of the virtual plane centering on the intersection line S of the C ₁ - C ₂ plane and the F plane, and the S Electrode A, which is insulated to cover the virtual surface of the upper half of C ₁ - _{C 2}
Divided into upper and lower planes by D ₁ - _{D 2} planes parallel to the plane,
It consists of two parts, electrode _A1 and electrode _A2 , which are insulated from each other. However, the area of electrode A ₁ and the area of electrode A ₂ are approximately equal. That is, the asymmetric probe of the present invention is an asymmetric three-electrode probe.

Now, insert this probe into the electric field so that the C ₁ - C ₂ plane is perpendicular to the lines of electric force, and connect the three electrodes A ₁ , A ₂ ,
When the potential of B is made to match the equilibrium potential, the distribution of the electric field becomes symmetrical with respect to the C ₁ - C ₂ plane as shown by the lines of electric force 1 and 1', which is different from the case in Figure 1. There is no place.

In this case, the A ₁ and A ₂ electrodes absorb only positive ion current, and the B electrode absorbs only negative ion current. Now, assuming that the respective currents are I ₊₁ , I ₊₂ , and I _- , these have the following relationships with the positive ion current density J ₊ and the negative ion current density J _- , respectively.

I ₊₁ ＝k ₁ J ₊ ……(3) I ₊₂ ＝k ₂ J ₊ ……(4) I ₊ ＝I ₊₁ ＋I ₊₂ ＝(k ₁ +k ₂ )J ₊ ＝kJ ₊ ……( 5) I _- = kJ _- ...(6) However, k ₁ and k ₂ are the geometrical shape of the probe and the electrode
A geometric coefficient determined by the dimensions of A ₁ , A ₂ , and B, determined by theoretical calculation or experiment. (i) For a spherical probe: k ₁ = 3πa ² (b/a) ² ...(7) k ₂ = 3πa ² [1-(b/a) ² ] ……(8) k=k ₁ +k ₂ = 3πa ² ……(9) (ii) For cylindrical probe: k ₁ = 4al(b/a) ...(10) k ₂ = 4al [1-(b/a)] ...(11) k = 4al ...(12). where a=probe radius, b=height of the _A2 electrode (see FIG. 2), and l=length of the axial electrode in the cylindrical electrode.

Therefore, at equilibrium potential, taking the ratio of I ₊₁ and I ₊₂ , (i) For a spherical probe: I ₊₁ /I ₊₂ = (b/a) ² /[1-(b/ a) ² ]
...(13) (ii) For cylindrical probe: I ₊₁ /I ₊₂ = (b/a)/[1-(b/a)]
...(14) In both cases, the ratio is a function of b/a.
In addition, even in the case of a general probe that is not spherical or cylindrical in shape, when the equilibrium potential is reached, the current ratio I ₊₁ /I ₊₂ of the A ₁ and A ₂ electrodes is determined by the geometric shape of the electrode,
A constant geometric coefficient γ (referred to as probe balance coefficient) specific to the dimensions is taken as I ₊₁ /I ₊₂ = γ (15). From this, conversely, measure the A ₁ and A ₂ electrode currents I ₊₁ ′ and I ₊₂ ′ while changing the probe potential, and manually or automatically determine the potential (equilibrium potential) at which the ratio is exactly γ above. Then, I ₊₁ and I ₊₂ can be immediately obtained as the current values of the A ₁ and A ₂ electrodes at that time,
From this, J ₊ can be found immediately using equation (5).

Also, from the current I _- of the B electrode at that time, J _- is determined by equation (6).
is found.

In this case, the detection of the equilibrium potential is performed at the equilibrium potential.
By choosing the division of the A ₁ and A ₂ electrodes so that I ₊₁ I ₊₂ , it becomes extremely easy and the accuracy can be greatly improved.

For example, for a spherical probe, from equations (7) and (8), b=a/√2...(16) For a cylindrical probe, from equations (10) and (11), b=a/2...(17) If selected, exactly I ₊₁ = I ₊₂ at the equilibrium potential, and the detection decision becomes reliable and easy.

The above is the basic structure and principle of the novel bipolar ion current probe according to the present invention.

That is, the novel bipolar ion current probe according to the present invention has a small virtual plane F having a plane-symmetrical shape with respect to the plane of symmetry, and a small virtual plane F having a plane-symmetrical shape with respect to the plane of symmetry, and a cross section S on both sides of the intersection line S where the plane of symmetry C ₁ - C ₂ intersects. On the virtual plane, the intersection line S
Measurement electrodes A and B are insulated and arranged symmetrically with respect to the plane C ₁ - _{C 2} so as to substantially cover the entire imaginary plane on both sides, apart from a small gap along the symmetrical plane. The electrode A is separated by a plane D ₁ -D ₂ parallel to the two partial electrodes A ₁ , separated from each other by a small gap.
The measurement electrodes _{A 1 ,} A ₂ , B
constitute an asymmetric three-electrode probe consisting of
This is insulated and supported by a hollow metal pillar for support, and insulated conductive wires are connected to the electrodes A ₁ , A ₂ , and B, respectively.
These conductive wires are passed through the insulation of the supporting hollow metal column, and the other ends of these conductive wires are connected to the terminals of minute ammeters D _A1 , D _A2 , D _B , respectively, and the D _A1 , D _A2 ,
Another terminal of _D Insert the A ₁ and A ₂ electrodes toward the positive ion source and the B electrode toward the negative ion source so that the plane of symmetry C ₁ - C ₂ is in the electric field. By changing the voltage V of the variable voltage source, the potentials of the electrodes A ₁ , A ₂ , B and the supporting hollow metal column are changed, so that the electrode A ₁ , A ₂ The ratio of the currents I ₊₁ ′ and I ₊₂ ′ of the minute ammeters D _A1 and D _A2 connected to
By calculating the value of I ₊₁ ′/I ₊₂ ′ and matching it with the above-mentioned probe balance coefficient γ corresponding to the equilibrium potential, the potential of the asymmetric three-electrode probe is matched to the original potential of the measurement point. Finally, find the readings of the microammeter at this time, I ₊₁ , I ₊₂ , and I _- , and find (I ₊₁ + I ₊₂ ) and I _-
The current density of positive and negative ions can be measured simultaneously and separately by utilizing the fact that the value of is proportional to the ion current density J ₊₁ and J _- of the polarity of the ion source where the respective electrodes face each other. .

The features and usage of the novel probe device according to the present invention will now be described in detail with reference to embodiments and drawings.

FIG. 3 shows an example in which the probe of the present invention can be realized as a spherical probe, and in the figure, 2 is the spherical probe portion. A _{hemispherical} electrode (A _{1 +}
A ₂ ) and B are arranged symmetrically and insulated with respect to the C ₁ - _{C 2} plane with a small gap, and the electrodes A ₁ and A ₂ are
Divided by plane D ₁ - _{D 2} parallel to C ₁ - C ₂ plane,
They are mutually insulated and have approximately the same surface area (b=a/√2 in the example of this figure) separated by a small gap.

3 is a hollow metal column for supporting the probe, which houses an insulating cylinder 4 to be brought into close contact with the inner surface, and an extension part 5 of 4.
fixedly supports the probe part 2 and inserts it at a required measurement point in an electric field where both positive and negative ions are present,
Arrange so that the C ₁ - C ₂ planes are perpendicular to the electric field.

Reference numerals 6, 7, and 8 are conductive wires having insulating shells that pass through the inside of the insulating cylinder 4, and each have an electrode A ₁ ,
A ₂ B, and the other end of each conductor is connected to one end of microammeters D _A1 , D _A2 , D _B which are insulated and supported. Further, the other ends of these minute ammeters are connected to a common conducting wire 9, and together with a conducting wire 10 attached to the metal column 3, are connected to a variable DC high voltage power source 11, thereby connecting each electrode A ₁ , A of the probe 2. ₂ ,
B is supplied with a common voltage V. Current voltage V
Adjust the readings of microcurrent meters D _A1 and D _A2 to I ₊₁ ′ and
The ratio of I ₊₂ ′ is the probe balance coefficient γ (in this example, γ
= 1, that is, I ₊₁ ′=I ₊₂ ′), then
The value of voltage V at this time matches the equilibrium potential, and the indicated values (equilibrium current values) (I ₊₁ , I ₊₂ , I _- ) of the minute ammeters D _A1 , D _A2 , D _B at this time When read, from equations (5), (6), and (9), I ₊ = I ₊₁ + I ₊₂ = 3πa ² J ₊ ……(18) I _- = 3πa ² J _- ……(19) immediately yields J ₊ , J _- can be found. In this case, the magnitudes of I ₊₁ ′ and I ₊₂ ′ are almost the same up to the equilibrium point, so the equilibrium coefficient γ is close to 1 (γ = 1 in the example shown in the figure), so the detection and determination of the equilibrium potential is is extremely easy. In this case, a microcurrent meter
An A-D converter and an electrical-to-optical signal converter are provided at D _A1 , D _A2 , and D _B to convert the values of I ₊₁ ′, I ₊₂ ′, and I _B ′ into digital signals, and then convert them into optical signals. The calculation control 1 consisting of a microprocessor or minicomputer etc.
5, calculate I ₊₁ ′/I ₊ ′ ₂ , and lead the output signal to the operation part of the DC high voltage power supply 11 through the conductor 16 so that it matches γ, and then I ₊₁ ′ /
After determining the currents I _{+1 ,} I ₊₂ , and I _- when I +2 ′ = γ, J ₊ J _- is calculated from the above equations (17) and (18), and this is displayed on the print section 17. It can also be displayed and printed.

FIG. 4 shows an embodiment in which the probe of the present invention is realized as a cylindrical probe, and FIG.
Figure b is a cross-sectional view of the probe portion. 18 in the figure is this cylindrical probe portion.
A semi-cylindrical electrode (A ₁ + A ₂ ) and B are separated by a small gap on a virtual cylindrical plane F whose plane of symmetry is the C ₁ - C ₂ plane.
C ₁ - C ₂ are arranged symmetrically and insulated against each other,
Further, electrodes A ₁ and A ₂ are divided by planes D ₁ - _{D 2} parallel to the C ₁ - _{C 2} plane, are mutually insulated, and have approximately equal surface areas separated by a small gap (in the example of this figure, b =
a/2).

3 is a hollow metal column for supporting the cylindrical probe;
An insulating cylinder 4 tightly housed therein extends beyond the electrodes A ₁ , A _{2 ,} and 3 of the cylindrical probe 18 .
B is supported and further extended to guard metal cap 1.
It carries 9. Thus, the cylindrical probe 18
There are two metal cylinders 13, 19 with the same outer diameter on both sides of the
This prevents the electric field from concentrating on the ends of the electrodes A ₁ , A ₂ , and B. The names and functions of elements numbered 6 through 17 in the figure are the same as those of the same numbered elements in FIG.

In this case, when the probe potential becomes the equilibrium potential,
From equations (5), (6), and (12), I ₊ =I ₊₁ +I ₊₂ =4alJ ₊ ...(20) I _- =4alJ _- ...(21) Therefore, immediately (I ₊₁ +I _{+ 2} ) and _I-, we can obtain the required J ₊ and J _- . Cylindrical probes are suitable for use with two-dimensional electric fields, and spherical probes are suitable for application with three-dimensional electric fields.

FIG. 5 shows an embodiment in which the novel probe according to the present invention is used as a sensor for reverse ionization diagnosis of an electrostatic precipitator performing pulse charging and for automatic control of pulse charging. 20 consists of a dust collection electrode 21 grounded in the dust collection chamber of the electrostatic precipitator, and a discharge electrode 22 insulated between the two, and 22 is a DC high voltage power source 23.
A high DC voltage Vdc with a value on the verge of the onset of negative corona is applied to 21 via the conductor 24, and in addition to this, a negative high voltage is applied from the high voltage pulse power source 27 via the conductor 25 and the coupling capacitor 26. A pulse V _p is applied, and a pulsed negative corona discharge is performed only when V _p is applied. Dust collection space 2
Dust particles entering 8 are given a negative charge by the impact of negative ions generated by negative corona discharge, and are removed onto the dust collecting electrode 21 by Coulomb force.
It is deposited here to form a dust group 29. Negative ions flow through this layer 29 and generate an electric field Ed=Jρd (22) within the layer. However, J is the negative ion current density and ρd is the dust resistivity. Therefore, when the resistivity ρd of the dust becomes too high and exceeds approximately 2×10 ¹⁰ Ω-cm, the electric field within the dust layer exceeds the breakdown value Eds, and Ed=J×ρ, d>Eds ……(23) Therefore, dielectric breakdown occurs and a so-called reverse corona is generated from this point, and positive ions are released.Therefore, in the dust collection space 28, a positive ion current flows toward the discharge electrode 22, and a negative ion current flows from the discharge electrode 22 toward the dust collection electrode. This will result in As a result, the electric charge of the dust particles is neutralized, and the dust collection performance is greatly reduced. In this case, the degree of charge reduction is determined by the current densities J ₊ and J _- of both positive and negative ions inside the dust collecting space 28. Therefore, by measuring this with the probe according to the present invention, the degree of harmfulness of the reverse corona can be diagnosed. in this case,
In the example shown in this figure, a spherical probe 2 is used, which is connected to a discharge electrode 22 and a dust collection electrode 2 by means of a supporting hollow metal column 3.
It is inserted in the middle of 1. D in the figure is the third
It is a set of D _A1 , D _A2 , D _B in the figure, 15, 17
are the same elements as 15 and 17 in the same figure. In this example, instead of the DC high-voltage power supply 11 for giving a balanced potential to the probe, a variable voltage divider 30 consisting of a resistor and a capacitor is inserted between the discharge electrode 22 and the dust collection electrode 21 to divide the applied voltage and By adjusting the partial voltage value, the probe voltage is varied, thereby providing an equilibrium potential. Once an equilibrium condition is established with an arbitrary DC voltage, the equilibrium state is maintained regardless of changes in the DC voltage or superimposition of pulse voltages. In this way, the calculation control unit 15 connected to D by the optical fiber 31 receives signals I ₊₁ ′, I ₊₂ ′,
I _B ′ is given as a digital optical signal, I ₊₁ ′/
The output signal is applied to the variable operating section 32 of the variable voltage divider 30 via the conductor 16 so that I ₊₂ ' = γ, and the voltage division ratio is changed so that an equilibrium potential is applied to the probe. Perform automatic control. Also, J ₊ and J _- are calculated from the values of I ₊₁ , I ₊₂ and I _B obtained at this time, and an operation signal is sent from 15 to the conductor 33 so that the value of J ₊ is set to zero and the reverse corona is eliminated. The negative pulse corona current supplied from the discharge electrode 22 is lowered by changing its pulse wave peak voltage V _p , pulse frequency _p , and pulse width τ _p . This eliminates the condition of equation (23) and eliminates the inverted corona. Furthermore, if the reverse corona becomes extremely active and cannot be eliminated even with these operations, it is necessary to lower V _dc or to bring it to zero in a short period of time. In such a case, the calculation control unit 15 judges this situation from the values of J ₊ and J _- and sends another signal to the conductor 34.
is applied to the DC high-voltage power supply 23 through the DC negative voltage V dc, and the DC negative voltage V _dc is gradually lowered, or periodically lowered to instantaneous zero and then returned to it.
Completely eliminate reverse corona.

In addition, the novel bipolar current probe device according to the present invention can be used to diagnose and automate all types of electrostatic precipitators (for example, three-electrode electrostatic precipitators having a third electrode in addition to a discharge electrode and a collection electrode). It can also be widely used for diagnosis and automatic control of control devices, powder dust collectors, electrostatic separators, etc.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing the basic structure of a bipolar ion probe according to the prior invention, Fig. 2 is a cross-sectional view showing the basic structure of the present invention, and Fig. 3 is a cross-sectional view and configuration of the present invention realized as a spherical probe. Figure 4 shows a cross section and configuration diagram of the present invention realized as a cylindrical probe, and Figure 5 shows an example in which the present invention is useful for reverse corona diagnosis and automatic control of an electrostatic precipitator that performs pulse charging. A configuration diagram is shown. In the figure, 1... Lines of electric force, A, B, C, A ₁ , A ₂ ... Probe electrode, C ₁ - C ₂ ... Plane of symmetry, F... Virtual plane of symmetry, D ₁ - D ₂ ... C ₁ - plane parallel to C ₂ plane, 3...
Supporting hollow metal column, D, D _B , D _A1 , D _A2 ...Micro ammeter, 11,23 ... DC high voltage power supply, 12,1
3, 14, 31... Optical fiber, 15... Calculation control section, 17... Instruction printing section, 27... High voltage pulse power supply, 30... Variable voltage divider.

Claims (1)

[Claims] 1. A small virtual surface F having a plane-symmetrical shape with respect to the plane of symmetry C ₁ -C ₂ , and the virtual surfaces on both sides of the intersection line S where the plane of symmetry C ₁ -C ₂ intersects. Above, measurement electrodes A and B are insulated and arranged symmetrically with respect to the planes C ₁ - _{C 2} so as to substantially cover the entire virtual planes on both sides, apart from a small gap along the intersection line S. , further separating the electrode A into two partial electrodes A ₁ separated by a small gap from each other by a plane D ₁ -D ₂ parallel to the plane of symmetry,
The measurement electrodes _{A 1 ,} A ₂ , B
An asymmetrical three-electrode probe consisting of
Connect insulated conductive wires to A ₁ , A ₂ , and B respectively, pass the insulation through the interior of the supporting hollow metal column, and connect the other ends of these conductive wires to the minute ammeters DA ₁ , DA ₂ , and DB, respectively. Connect to the terminal, the DA ₁ ,
Connect the other terminal of DA ₂ and DB to the supporting hollow metal column using a common conductor, connect this to a variable voltage source to configure one measurement system, and connect the asymmetric three-electrode probe to the After inserting it into a measurement point in an electric field where ion current and negative ion current coexist, point A ₁ and A ₂ toward, for example, a positive ion source and the B electrode toward, for example, a negative ion source, so that the symmetry plane C ₁ - C ₂ is The electric potential of the electrodes A ₁ , A ₂ , B and the hollow metal column for support is changed by changing the voltage V of the variable voltage source. The ratio of the currents I _{+1 ′} and I +2 ′ of the minute ammeters DA ₁ , DA ₂ connected to _A 1 and A ₂
By matching the value of I ₊₁ ′/I ₊₂ ′ with the probe balance coefficient γ detailed in the text corresponding to the equilibrium potential, the potential of the asymmetric three-electrode probe is made to match the original potential of the measurement point. , the reading of the microcurrent meter at this time
I ₊₁ , I ₊₂ , I _- are determined, and the values of (I ₊₁ + I ₊₂ ) and I _- are proportional to the polarity, e.g., positive and negative ion current density, from the ion source where electrode A and electrode B face each other. A bipolar ion current probe device characterized in that it measures the current density of positive and negative ions simultaneously and separately by taking advantage of the fact that: 2. Claim 1, which is characterized in that a variable voltage divider is inserted in parallel with the power supply that supplies voltage to the system under test as a variable voltage source, and the divided voltage of the output voltage is used. A bipolar ion current probe device as described. 3 The measured current value is converted from analog to digital using the minute ammeters DA ₁ , DA ₂ , and DA ₃ and further converted into an optical digital signal. This is supplied to the calculation control section at ground potential through an optical fiber, and the calculation control section receives the I ₊₁ ′/I ₊₂ ′ is calculated, and the calculation control unit supplies and controls an operation signal to the variable voltage source or the adjustment operation unit of the variable voltage divider so that the value matches γ; This automatically makes V match the equilibrium potential and
The bipolar ion current probe device according to claims 1 and ₂ , characterized in that J ₊₁ and J _- are calculated and displayed from the values of I +1 _, I +2 and IB.