JPH0943287A - Orthogonal converter for vibration capacity type potentiometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an orthogonal converter of a vibration capacity type potentiometer which requires neither a bias magnet nor a multiplier (or a frequency divider). SOLUTION: An orthogonal converter 8 has a residual magnetic type vibration electrode 37. The residual magnetic type vibration electrode 37 vibrates at a vibration frequency (f) by a magnetic field varying cyclically at a frequency (f) as generated by an electromagnetic coil 22. In other words, the residual magnetic type vibration electrode 37 is made up of a conducting material and a residual magnetic material and the conducting material functions as one electrode of a capacitor so that the residual magnetic material works to generate an attracting force and a repulsive force with respect to the magnetic field. Thus, the frequency of an output signal of the orthogonal converter 8 equals the frequency (f) of the signal generated by the oscillator 56 thereby eliminating the need for a multiplier or a frequency device. This also requires no bias magnet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillating capacitance electrometer used for measuring a signal from a radiation detector, and more particularly to a structure of an orthogonal transformer which does not require a bias magnet or a multiplier.

[0002]

2. Description of the Related Art An oscillating capacitance type electrometer is used for amplifying and measuring a weak signal (charge) from a radiation detector such as an ionization chamber having a high output impedance because the input bias current is extremely small. It The oscillating capacitance type electrometer is a quadrature converter that converts the captured charge from direct current to alternating current, a synchronous detector that performs synchronous detection on its output,
Also, it is composed of an electrometer for measuring the potential of the synchronously detected signal.

FIG. 8 shows a sectional view of a conventional orthogonal transformer. Further, FIG. 9 shows a block diagram of a main part configuration of a conventional vibration capacitance type electrometer including the orthogonal converter.

In FIG. 8, a container 10 made of stainless steel is shown.
Is composed of a cylindrical body 12, an upper lid 14 and a bottom plate 16, the inside of which is made an airtight space and filled with an inert gas. A base 18 is arranged below the bottom plate 16, and a bias magnet 20 and an electromagnetic coil 22 are arranged on the base 18. These operations will be described later.

Inside the container 10, a screw 24 is erected on the bottom plate 16 as a pillar, and a horizontal stand 26 is held by the screw 24. Here, the height of the horizontal base 26 can be adjusted by a height adjusting mechanism 28 including the screw 24 and a nut screwed with the screw 24. A pedestal 32, which is made of alumina ceramic or the like and serves as an insulating substrate, is supported and fixed on the horizontal table 26 by columns 30.
A counter electrode 36 plated with gold by an insulator 34 made of sapphire or the like held by a horizontal table 26.
Is fixedly supported. The counter electrode 36 has a funnel-shaped outer shape, and the electrode surface at the tip thereof faces the vibrating electrode 38.

The vibrating electrode 38 in the form of a rectangular thin plate is, for example, a surface of a magnetic material plated with gold so as to have conductivity. Conventionally, the thickness thereof is, for example, 0.5 mm, and one end thereof has a holding portion 41. It is held and vibrated by. The magnetic material is a ferromagnetic material (however,
Conventionally, for example, a nickel material, which has no residual magnetism, is used. The vibrating electrode 38 is a thin partition wall 4 that forms a part of the bottom plate 16 when it vibrates.
The height is adjusted so as not to contact the zero electrode and the counter electrode 36. Here, the distance between the tip surface of the counter electrode 36 and the vibrating electrode 38 can be adjusted by the height adjusting mechanism 28 described above. The partition wall 40 is made of a stainless material or the like and has a thickness of, for example, 3 mm, and reduces electromagnetic noise generated in the electromagnetic coil 22.

In this conventional example, a double-cylindrical condenser 42 is fixed to the pedestal 32. Specifically, the condenser 42 is composed of an inner cylinder 44 and an outer cylinder 46. Inner cylinder 4
4 contains a resistor 48 having a high resistance value in order to reduce the influence of noise. In addition, 50 and 52 are insulating members made of sapphire or the like.

As described above, in this orthogonal converter, the condenser 42, the vibrating electrode 38 and the counter electrode 36 are provided.
And a variable capacitance type capacitor 39 composed of (1) and (3) are connected in parallel (see FIG. 9).

In FIG. 8, the electric charge from, for example, the ionization chamber is taken into the terminal a electrically connected to the counter electrode 36 through the resistor 48, and the conductive substrate and the signal line are provided in the outer cylinder 46 of the capacitor 42. An output signal is taken out from the terminal c electrically connected via the. The vibrating electrode 38 has a terminal b.
Are electrically connected, and the terminal b thereof is grounded, for example.
Further, a drive signal having a sine wave of about several kHz is supplied between the two terminals d.

When a drive signal is supplied to the electromagnetic coil 22, an alternating magnetic field is generated by the electromagnetic coil 22 and vibrates the vibrating electrode 38 made of a magnetic material. At this time, due to the action of the bias magnet 20, the bias magnetic field acts on the vibrating electrode 38 in addition to the alternating magnetic field, and a pulsating magnetic field is applied by both of them.

Now, when the charge Q is taken in from the terminal a, the charge is distributed according to the capacitance ratio of the two capacitors 39 and 42. For example, the charge Q on the capacitor 39
1 is accumulated, and the charge Q2 is accumulated in the capacitor 42 (Q = Q1 + Q2). However, when the inter-electrode distance of the capacitor 39 changes due to the action of the alternating magnetic field generated in the electromagnetic coil 22, and thus the capacitance of the capacitor 39 changes, the distribution ratio of the charge Q changes according to the change in the capacitance. It will be. Then, the change appears as an AC signal at the terminal c.

FIG. 10 shows the operation of the conventional orthogonal transformer in the absence of a bias magnetic field, and FIG. 11 shows the operation of the conventional orthogonal transformer in the presence of a bias magnetic field. Here, changes in the magnetic field over time are shown in (A) of FIGS. 10 and 11, changes in the force received by the vibrating electrode 38 are shown in (B), and (C) is shown. The displacement is shown.

As shown in FIG. 10A, when no bias magnetic field is present and only an alternating magnetic field of frequency f is generated, the alternating magnetic field causes the vibrating electrode as shown in FIG. 10B. The force received by 38 has the maximum attractive force when the alternating magnetic field has a maximum in positive and negative directions, that is, the attractive force with respect to the vibrating electrode 38 is proportional to the absolute value of the current flowing in the electromagnetic coil. In this case, it is understood that the vibrating electrode 38 vibrates at the frequency 2f, as shown in FIG.

On the other hand, as shown in FIG. 11, when a bias magnetic field having a constant magnetic field strength is applied to the alternating magnetic field of frequency f, the vibrating electrode 38 changes periodically as shown in FIG. 11 (B). Then, the vibrating electrode 38 vibrates at the frequency f, as shown in FIG. 11C. That is, when the bias magnetic field is applied, the vibration frequency of the vibration electrode 38 can be matched with the frequency of the drive signal of the electromagnetic coil. As shown in FIG. 11A, the magnitude of the bias magnetic field is such that the polarity does not change even if it changes, that is, the positive side (or the negative side).
It is set so that an alternating magnetic field is generated only at. The frequency of the drive signal is set so that the vibration frequency of the vibrating electrode 38 is at or near the resonance frequency of the vibrating electrode 38.

FIG. 9 schematically shows the structure of a conventional oscillating capacitance type electrometer including the orthogonal transformer 54. The oscillator 56 supplies a drive signal of frequency f to the electromagnetic coil 22. As described above, this driving signal causes the electromagnetic coil 22 to generate an alternating magnetic field, and the pulsating magnetic field obtained by adding the bias magnetic field of the bias magnet 20 to the alternating magnetic field vibrates the vibrating electrode 38 in FIG. This vibration changes the capacity ratio between the two capacitors,
The change appears as an output signal at the terminal c. The output signal is amplified by the AC amplifier 58, and is further divided by the voltage divider 6
It is amplified in the AC amplifier 62 via 0, and the amplified signal is sent to the synchronous detector 64.

On the other hand, the drive signal from the oscillator 56 is also supplied to the waveform shaper 66, which converts the sine wave into a rectangular wave and outputs it as a detection reference signal. The detection reference signal is subjected to phase adjustment for synchronous detection in the phase shifter 68, and then the synchronous detector 6
4 is supplied.

In the synchronous detector 64, the detection reference signal becomes a switching signal, the positive and negative polarities of the signal output from the AC amplifier 62 are discriminated, and the detected signal is amplified by the DC amplifier 70. , To the next electrometer (not shown). In addition, via the feedback element 72,
The detected signal is fed back, which stabilizes the operation of the circuit.

Incidentally, when the bias magnet 20 is not used, the frequency of the signal output from the quadrature converter is 2f with respect to the frequency f of the drive signal, as shown in FIG.
Becomes Therefore, in order to perform synchronous detection, the oscillator 5
It is necessary to double the frequency of the signal output from 6 in the multiplier (2f) and supply it to the synchronous detector 64. Alternatively, in order to use the frequency f as it is in the synchronous detection, the frequency f of the drive signal is divided by 1 /
It is necessary to divide the frequency by 2 and supply it to the electromagnetic coil, thereby generating a magnetic field of frequency f / 2 to set the vibration frequency of the vibration electrode 38 to f.

[0019]

By the way, in the above-mentioned conventional vibrating capacitance electrometer, there is a demand for eliminating the need for a bias magnet in order to reduce the size and weight of the device.
However, if the bias magnet is removed, the vibration frequency of the vibrating electrode becomes twice as high as the drive signal of the electromagnetic coil, so that the multiplier or frequency divider is required as described above. Such a circuit requires a relatively complicated circuit configuration based on a PLL or the like, and cannot reduce the cost of the device.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to provide a quadrature converter of an oscillating capacitance type electrometer which does not require a bias magnet or a multiplier (or frequency divider). Especially.

[0021]

In order to achieve the above object, the present invention provides a counter electrode fixedly arranged, and a vibrating electrode which is arranged in close proximity to the counter electrode in a non-contact manner and is vibratably supported. An electromagnetic coil which is arranged in the vicinity of the vibrating electrode and which is supplied with a drive signal of a frequency f and generates a magnetic field which fluctuates periodically; and the vibrating electrode is composed of a conductive material and a residual magnetic material, The vibration frequency of the vibration electrode is the same as the frequency f.

According to the above construction, the frequency f is applied to the electromagnetic coil.
When the drive signal is generated, a magnetic field whose polarity fluctuates alternately at the frequency f is generated, and the magnetic field vibrates the vibrating electrode at the frequency f. That is, the conductive material included in the vibrating electrode serves as one electrode of the capacitor, and the residual magnetic material included in the vibrating electrode causes an attractive force or a repulsive force corresponding to the polarity of the external magnetic field. That is, in the case of a mere magnetic material, an attractive force is generated according to the strength of the magnetic field regardless of the polarity, but according to the present invention, by utilizing both attractive force and repulsive force, The fluctuation frequency of the magnetic field can be matched.

Therefore, if an oscillating capacitance type electrometer is constructed using the quadrature converter according to the present invention, for synchronous detection,
It is not necessary to prepare a bias magnet, and it is not necessary to prepare a multiplier (or frequency divider).

[0024] In a preferred aspect of the present invention, the vibrating electrode is formed by laminating a conductive material layer and a residual magnetic material layer. Further, in a preferred aspect of the present invention, the vibrating electrode is configured by mixing a conductive material and a residual magnetic material. Further, in a preferred aspect of the present invention, the vibrating electrode is configured by joining a magnet piece as a residual magnetic material to a conductive material layer. The function of the magnet piece is different from that of the conventional bias magnet, and the magnet piece generates the attractive force and the repulsive force as the residual magnetic material.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below based on the present invention.

FIG. 1 shows the overall configuration of a vibrating capacitance type electrometer including an orthogonal converter according to the present invention. Further, FIG. 2 shows a preferred embodiment of the orthogonal transformer according to the present invention. 1 and 2, the same components as those of the conventional configuration shown in FIGS. 8 and 9 are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 1, a remanent magnetism type vibrating electrode 37 is used as a vibrating electrode in the orthogonal transformer 8 in this embodiment. By using such a remanent magnetism type vibrating electrode 37, it is possible to remove the bias magnet and the multiplier. It should be noted that, in comparison with the prior art, only the configuration of the vibrating electrode is basically different.

As shown in FIG. 2, in the orthogonal transformer of the present embodiment, the bias magnet 2 that has been conventionally provided is used.
0 (see FIG. 8) is not provided, and the shape of the orthogonal transformer is reduced in size and weight accordingly.

The remanent magnetic vibrating electrode 37 contains a conductive material and a remanent magnetic material. The conductive material serves as one electrode of the capacitor, and the residual magnetic material functions to vibrate the vibrating electrode. However, what is different from the prior art is that the vibrating electrode is magnetized in advance, and such residual magnetism can generate an attractive force and a repulsive force with respect to an external magnetic field. Its magnetization is in the vertical direction.

The operation of the remanent magnetism type vibrating electrode 37 will be described with reference to FIG. FIG. 3A shows the change over time of the magnetic field generated by the electromagnetic coil 22. FIG.
(B) shows the force generated in the vibrating electrode by the magnetic field. As understood from this (B), it is understood that the force acts on the vibrating electrode in perfect agreement with the fluctuation of the sinusoidal magnetic field shown in (A). That is, the attractive force and the repulsive force are working alternately. Therefore, as shown in (C) of the displacement of the vibrating electrode, the vibrating electrode vibrates at the frequency f of the drive current supplied to the electromagnetic coil 22.

Therefore, in FIG. 1, since the frequency of the output signal of the orthogonal converter 8 is f, the frequency f of the signal output from the oscillator 56 is used as it is, and the synchronous detector 64 is used.
Thus, it becomes possible to perform synchronous detection on the output of the orthogonal converter 8. That is, synchronous detection can be performed with a single frequency without using a bias magnet or a multiplier. The remanent magnetism type vibrating electrode 37 is magnetized in advance by a permanent magnet or the like.

4 to 7, the remanent magnetism type vibrating electrode 37 is shown.
Various embodiments of are shown. In each figure, the remanent magnetism type vibrating electrode 37 and the counter electrode 36 are schematically shown, and 106 in each figure is a spacer as an insulator.

In the example shown in FIG. 4, the remanent-magnetic vibrating electrode 37 is formed by forming the conductive material layer 100 on the surface of the remanent-magnetic material layer 102. For example, the conductive material layer 100 can also be formed by vapor deposition or coating.

Here, for example, gold or aluminum is used as the conductive material. Further, as the residual magnetic material, for example, a permanent magnet material such as a nickel-based material or a cobalt-based material, which is a hard magnetic material that causes residual magnetization among ferromagnetic materials, is used.

In the example shown in FIG. 5, the conductive material layer 1
The remanent magnetic material layer 102 is formed on the back surface of No. 00.

In the example shown in FIG. 6, the remanent magnetism type vibrating electrode 3 is used.
7 is configured as a mixture or alloy of the conductive material 37A and the residual magnetic material 37B. Of course, the vibrating electrode 37 is made of a material that exhibits both conductivity and residual magnetism.
Can also be configured.

In the example shown in FIG. 7, the conductive material layer 1
A magnet piece 104 as a residual magnetic material is joined and arranged on the back surface of 00. This magnet has a function different from that of the conventional bias magnet, and generates an attractive force and a repulsive force with respect to the periodically varying magnetic field generated by the electromagnetic coil 20.

[0038]

As described above, according to the present invention,
Since the vibrating electrode is composed of the conductive material and the residual magnetic material,
The one electrode of the vibration capacitance type capacitor can be realized by the conductive material, and the attractive force and the repulsive force can be generated by the residual magnetic material with respect to the magnetic field generated in the electromagnetic coil. Therefore, the vibration frequency of the vibrating electrode can be made equal to the frequency f of the drive signal, and a bias magnet, a multiplier (or a frequency divider), etc. are unnecessary.

[Brief description of drawings]

FIG. 1 is a diagram showing an entire configuration of a vibrating capacitance type electrometer including an orthogonal transformer according to the present invention.

FIG. 2 is a sectional view of an orthogonal transformer according to the present invention.

FIG. 3 is a diagram showing an operation of the remanent magnetism type vibrating electrode 37 shown in FIG.

FIG. 4 is a diagram showing an example of a remanent magnetism type vibrating electrode.

FIG. 5 is a diagram showing an example of a remanent magnetism type vibrating electrode.

FIG. 6 is a diagram showing an example of a remanent magnetism type vibrating electrode.

FIG. 7 is a diagram showing an example of a remanent magnetism type vibrating electrode.

FIG. 8 is a sectional view showing a conventional orthogonal transformer.

FIG. 9 is a diagram showing an overall configuration of a conventional vibration capacitance type electrometer.

10 is a diagram showing the operation of the orthogonal transformer when the bias magnet 20 shown in FIG. 9 is not used.

FIG. 11 is a diagram showing an operation of the orthogonal transformer when the bias magnet shown in FIG. 9 is used.

[Explanation of symbols]

22 electromagnetic coil, 36 counter electrode, 37 remanent magnetism type vibrating electrode, 39 capacitor, 56 oscillator, 64 synchronous detector, 100 conductive material layer, 102 remanent magnetic material layer, 104 magnet piece.

Claims (4)

[Claims] 1. A counter electrode fixedly arranged, a vibrating electrode which is disposed in proximity to the counter electrode in a non-contact manner and is oscillatably supported, and a drive signal having a frequency f which is arranged in the vicinity of the vibrating electrode. And a vibrating electrode composed of a conductive material and a remanent magnetic material, wherein the vibrating frequency of the vibrating electrode is the same as the frequency f. A quadrature converter of the characteristic vibrating capacitance electrometer. 2. The orthogonal transducer according to claim 1, wherein the vibrating electrode is formed by laminating a conductive material layer and a remanent magnetic material layer. 3. The orthogonal transformer of a vibrating capacitance electrometer according to claim 1, wherein the vibrating electrode is formed by mixing a conductive material and a residual magnetic material. 4. The orthogonal transducer according to claim 1, wherein the vibrating electrode comprises a conductive material layer and a magnet piece as a residual magnetic material bonded to the vibrating electrode. Orthogonal transformer.