JPH0271166A - Surface potential sensor - Google Patents

Abstract

PURPOSE:To improve measurement accuracy and reduce in size and weight by forming a sound reed, a measurement electrode and a circuit part with the same member (substrate). CONSTITUTION:A substrate (highly elastic plastic plate) 1 is fixed on a fixing member 2 with screws 8. A part of the substrate 1 is cut out by etching or machining to form a sound reed 3, and a measurement electrode 4 is formed on the tip of said reed 3. The electrode 4 is connected to a rear pattern via a through hole, and said pattern is connected to a preamplifier circuit 6. A piezoelectric element 5 is adhered to the vicinity of the supporting base of the sound reed 3. Driving signals and feedback signals are input to a driving circuit 7. The substrate 1 is equipped with a recess 9 for escaping vibration of the sound reed 3. This sensor is used while being covered by a console (shield case) having an opening. Relative positional relation among the respective elements 1, 3, 4 and the positional relation among the elements 1, 3, 4 and the console opening thus can be determined accurately. This improves accuracy for measuring potential.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a surface potential sensor that measures surface potential in a non-contact manner.

[Conventional technology]

Conventionally, as an AC type surface potential sensor, a rotating sector type, a vibration capacitive type in which the measuring electrode itself vibrates, or a vibrating sector type in which a part of a chopper is provided at the tip of a tuning fork have been used. In particular, the chopper drive type using a tuning fork has become mainstream because it is compact and can easily produce high-amplitude stable vibrations, along with improved performance of piezoelectric elements.

[Three problems to be solved by the invention] However, in this chopper drive system using a tuning fork, the tuning fork, its supporting member, the circuit section, and the frame of the surface potential sensor are all composed of independent members or parts. As a result, the following problems occurred.

(1) There was a certain limit to the assembly granularity of each member, and it was difficult to determine the relative positional relationship of the tuning fork, measurement electrode, and measurement window (the opening in the frame facing the surface to be measured) with good dimensional accuracy. For this reason, it was not possible to increase the measurement accuracy beyond a certain level.

(2) The size in the thickness direction (rX) after assembly is large, and there is a certain limit to miniaturization or weight reduction.

(3) The assembly process became complicated and the cost increased.

In addition, there were the following problems. That is, it is difficult to process the signal line for amplifying the very high impedance minute signal induced in the measurement electrode so that it is not affected by other external noise, especially the drive signal for the piezoelectric element.

This invention was made to solve these conventional problems; (1) measurement accuracy can be improved;
The present invention aims to provide a surface potential sensor that (2) is small and lightweight, (3) is easy to assemble and can be automated, thus reducing manufacturing costs, and (4) is not adversely affected by external noise.

[Means to solve the problem]

In order to achieve the above object, in the surface potential sensor of the present invention, the vibrating bar and the measurement electrode 1 circuit section are formed of the same member (substrate).

In addition, when two vibrating bars are provided, they are provided symmetrically around the supporting portion so that they vibrate in opposite phases to each other to maintain balance.

Furthermore, when two sound bars are provided, a second measurement electrode is provided on one of the sound bars on which no measurement electrode is provided, symmetrically with the measurement electrode of the other sound bar, and the signal is sent to the amplifier circuit. input to the differential input.

[Effect]

In this invention, since the vibrating bar and the measuring electrode 9 circuit part are formed of the same material (substrate), the vibrating bar, the measuring electrode, and the measuring window (
The positional relationship of the openings in the frame can be determined with high dimensional accuracy. Therefore, the accuracy of potential measurement can be improved.

Furthermore, for the same reason, the thickness of the surface potential sensor can be reduced, making it possible to make it smaller and lighter. Since the assembly process is simplified, it can be automated and manufacturing costs can be reduced.

Furthermore, when two sound bars are provided, their vibrations are balanced with each other, so there is no leakage of vibrations to the outside, and the sound bars are not adversely affected by external noise.

When two sound bars are provided, a second measurement electrode is provided symmetrically to the measurement electrode of the other sound bar on one sound bar without a measurement electrode, and the signal is transmitted to the differential of the amplifier circuit. Since the voltage is input to the input, noise components other than the surface potential of the object to be measured can be canceled out by amplifying the difference between the voltage and the induced voltage of the second electrode. Therefore, high-level potential measurements can be made.

〔Example〕

(Example 1) FIG. 1 shows a first embodiment of the invention.

In the figure, 1 is a board, and 2 is a mounting member for the board 1.

The board 1 is fixed to a mounting member with screws 8. Reference numeral 3 designates a vibrating bar formed by cutting out a part of the substrate by etching or cutting, and 4 designates a measurement electrode formed at the tip of the vibrating bar 3. The measurement electrode 4 is connected to a back side pattern through a through hole, and the same pattern is connected to a preamplifier circuit 6. Reference numeral 5 denotes a piezoelectric element, which is glued near the support portion of the vibrating bar 3. The drive signal and the 9-pass signal are input to the drive circuit 7. Reference numeral 9 denotes a recess provided in the substrate 1 to release vibrations of the vibrating bar 3.

As shown in FIG. 2, the substrate 1 is a highly elastic resin plate 11 on both sides of which a measuring electrode 4 and a circuit pattern are formed using conductors 11i10a and 10b. The conductive film 10a, job may be formed by plating or painting, or may be formed by laminating conductive metal thin films. The measurement electrode 4 and the circuit pattern are formed in the same process as a normal printed wiring board (printed board).

As shown in FIG. 3, the substrate 1 is made by printing insulation 11Q 13 on a highly elastic metal thin plate 12 made of phosphor bronze, Nilin 8, etc., and then printing a conductive film 14 thereon to form a measurement electrode 4 and a circuit pattern. It may also be formed by

The insulating film 13 is formed by coating an insulating agent or by baking an insulating film. The conductive film 14 can be formed by baking or vapor depositing a conductive paint.

The surface potential sensor of this embodiment is used by covering it with a frame (shield case) 15 having an opening 16, as shown in FIG.

Next, the effect will be explained.

In the sensor of the embodiment, the sound bar 3 is made by cutting out the measurement electrode 4 and the substrate 1 on which the circuit pattern is formed, so that
Since the vibrating bar 3, the measuring electrode 4, and the circuit pattern are formed on one substrate 1, the relative positional relationship of each element 1, 3.4 can be determined with high dimensional accuracy. Furthermore, the positional relationship between the opening 16 of the frame 15 and each of the above-mentioned elements 1, 3.4 can be determined with high precision. Therefore, the accuracy of potential measurement is improved.

Furthermore, for the reasons mentioned above, the thickness of the surface potential sensor is reduced, so the sensor can be made smaller and lighter. Furthermore, the manufacturing of the substrate 1 and the cutting out of the sound bars 3 are relatively simple, allowing for automation. Therefore, manufacturing costs can be reduced.

(Example 2) FIG. 5 shows a second example. In this embodiment, a pair of sound pieces 3a and 3b are formed by cutting out a substrate 1 and are provided symmetrically with respect to their support portions.

The piezoelectric elements 5a, 5b are symmetrically bonded to the vibrating bars 3a, 3b. One of the pressure elements 5a and 5b is used for driving and the other for vibration detection. In the figure, the same parts as in FIG. 1 are given the same reference numerals.

According to this embodiment, the vibrating bars 3a and 3b are balanced by vibrating in opposite phases to each other as shown in FIG. 6, so there is no leakage of vibration to the outside, and the vibrating bars 3a and 3b are is not adversely affected by mechanical noise. Further, there is an advantage that the weight of the member to which the substrate 1 is attached can be reduced. Other effects are the same as in the first embodiment.

(Embodiment 3) FIG. 7 shows a third embodiment. In this embodiment, a second electrode 4a is provided at the tip of the vibrating bar 3b in the second embodiment at a position symmetrical to the measuring electrode 4 of the vibrating bar 3a.
The signal a is input to the differential input of the preamplifier 6.

According to this embodiment, noise components other than the surface potential of the object to be measured induced in the measurement electrode 4 can be canceled out by amplifying the difference between the induced voltage of the second electrode 4a and the It becomes possible to measure the potential of the degree of turbulence. Other effects are the same as in the first embodiment.

〔Effect of the invention〕

As explained above, according to the present invention, (1) it is possible to improve the accuracy of potential measurement, (2) it is small and lightweight, and (3) it is easy to assemble and can be automated, thus reducing manufacturing costs. (4) It is possible to obtain a surface potential sensor that is not adversely affected by external noise.

[Brief explanation of the drawing]

FIG. 1 shows a first embodiment of the present invention, in which (a) is a top view, (b) is a side view, (e) is a bottom view, and (e) is a bottom view.
The figure is a side view of the board in Fig. 1, Fig. 3 is a side view showing another aspect of the board in Fig. 1, and Fig. 4 is a side view showing a state in which the sound piece in Fig. 1 is covered with a frame. , FIG. 5 is a top view of the second embodiment, FIG. 6 is a side view showing the vibration state of the sound bar in FIG. 5, and FIG. 7 is a top view of the third embodiment. 0b Laugh 1 Missing Hii Ut 2 9'l Basic story, Nono] View 2nd
Diagram...Board...Sound bar...Measuring electrode...Piezoelectric element...Preamplifier circuit...Drive circuit board Understand. 1 Side view Figure 3

Claims (6)

[Claims] (1) A substrate, a cantilever sound piece formed by cutting out a part of the sound piece, a piezoelectric element glued to this sound piece, a measurement electrode provided at the tip of the sound piece, and a piezoelectric element provided on the substrate. A surface potential sensor that includes a drive circuit and an amplification circuit for an alternating current signal induced in a measurement electrode provided on a substrate. (2) The surface potential sensor according to claim 1, wherein the substrate comprises a highly elastic thin metal plate and a measurement electrode and a circuit pattern formed of a conductive film provided thereon via an insulating film. (3) The surface potential sensor according to claim 1, wherein the substrate comprises a highly elastic insulating plate and a measurement electrode and a circuit pattern formed by etching a conductive film provided on both sides of the board. (4) The surface potential sensor according to any one of claims 1 to 3, wherein two vibrating bars are provided symmetrically with respect to each other around the support portion, and both vibrating bars vibrate in opposite phases to each other. (5) A piezoelectric element for driving and a piezoelectric element for vibration detection are glued to each of the two vibrating bars, and both piezoelectric elements are connected to the output and input of a predetermined amplifier, respectively, and the amplifier is energized. 5. The surface potential sensor according to claim 4, wherein the surface potential sensor automatically oscillates at a resonance frequency specific to the vibrating bar. (6) Of the two sound pieces, the sound piece that is not equipped with a measurement electrode,
6. The surface potential sensor according to claim 4, wherein a second measuring electrode is provided symmetrically to said measuring electrode, and the signal thereof is inputted to a differential input of an amplifier circuit.