JPS60152959A - Potential sensor - Google Patents

Abstract

PURPOSE:To enable the measurement of a correct electrostatic field by a differential amplification of output voltages from two electrodes. CONSTITUTION:Two detection electrodes 3a and 3b are arranged on a substrate 8 so as to be varied in the height and output voltages Va and Vb outputted from output terminals 5a and 5b of the electrodes 3a and 3b are supplied to amplifiers 11 and 12 of a differential amplification section. The output voltages Va and Vb of the terminal 5a and 5b have different distance characteristics and hence, output voltages V1 and V2 of the amplifiers 11 and 12 are inputted into a differential amplifier 13 through a resistance R1. The output voltage V3 thereof 13 indicates a surface potential of an object to be measured free from distance by setting the voltages V1 and V2 here and the resistance ratio R1/R2 at specified values respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Science and Technology) The present invention relates to a potential sensor v1, particularly a potential sensor used for detecting the strength of an electrostatic field, measuring the amount of charge, etc.

(Prior art) In general, potential sensors have two types: one that waits for a detection hole to introduce the lines of electric force radiated from the foot to be measured vIJ, and the other that waits for a detection hole to introduce the lines of electric force radiated from the foot to be measured, and the other that waits for a detection hole to introduce the lines of electric force that enter the case. It consists of a part and one pole for receiving this cut electric force lIM and taking out an exchange signal.

FIGS. 1(a) and (b) are fl;f:n-conventional'
1 is a plan sectional view and a side sectional view showing an example of a potential sensor.

In the figure, a tuning fork 2 to which piezoelectric ceramics 6 for driving is bonded is used in the chopper part, and lines of electric force 7 are cut at the base ends 2aν and 2b of the tuning fork 2 to drive terminals 4. An output terminal 5 and a ground terminal 9 are attached, and necessary internal wiring is provided between the tuning fork drive terminal 4 and the piezoelectric ceramic 6.

Next, Figure 2 shows the distance tF of the potential sensor that is missing in Figure 1! j
This is a characteristic diagram showing an example of the characteristics of the output terminal 5 (shown in Figure 1).
The output voltage from ■ changes. That is, even if a plurality of objects to be measured are charged with the same surface potential, the value of the output voltage (2) will differ depending on the distance (measurement distance) D from each object to the potential sensor. Therefore, as shown in Figure 1, it is necessary to fix the potential sensor at a certain distance from the object to be measured and then calibrate it by applying a known surface potential to the object. Since the output voltage fluctuates greatly due to this, the mounting accuracy is often required to be very strict.

(Object of the invention) The object of the invention is to provide a potential sensor that eliminates the above drawbacks by differentially amplifying the output voltage from two electrodes, and that enables accurate measurement of electrostatic fields, etc. Smell.

(Structure of the Invention) According to the invention, there is provided a chiro-flange part that cuts the electric lines of force radiated from the object to be measured at regular intervals, and an electrode part that receives the electric flux lines cut by the chiro-flange part. , a potential sensor including a substrate on which the teat flange portion and the electrode portion are mounted, and a case housing the substrate and having a detection hole for introducing the electric line of force, the electrode portions being mutually connected to each other. It consists of two electrodes placed on the substrate at different heights, and the output voltage from the electrodes is connected to differential amplification means.

FIGS. 3(a), (b) and (C) are a plan sectional view, a side sectional view and a perspective view showing one embodiment of the sensor portion of the potential sensor of the present invention, respectively, in the P gun. , the same reference numerals as in FIG. 1 indicate the same components as in the conventional example. In this embodiment, the substrate 8 includes two detection electrodes 3a,
3b and the tuning fork 2 attached at the chopper part) are attached tL,
The detection electrodes 3a and 3b are arranged at different heights. Therefore, the output voltages detected by the detection electrodes 3a and 3b and outputted from the output terminals 5a and 5b are different from each other and have alternating characteristics.

Next, a method for removing the distance characteristic using an uninvented potential sensor will be explained. The distance characteristic of the conventional potential sensor shown in FIG. 2 is expressed by the following equation.

V=E(-10b)・・・・・・・・・・・・(1
) Here, V is the output voltage, E is the surface potential of the object to be measured, D is the distance between the object to be measured and the potential sensor, and a and b are constants.

Therefore, by changing the distance and measuring at two or more points, the constants a and b are determined, and the distance characteristic shown in FIG. 2 is uniquely determined. Output terminal 5 even if it is 2 in non-implemented example
a, 5b to n-5rt, output voltage va,
Vb has the same distance characteristics as above, but the output voltage v
By combining a and Vb, the surface potential of the object to be measured can be measured without depending on the distance. The formula expressing the distance characteristics at the detection electrodes 3a and 3b is as follows.
・・・(2Vb=E (B+bz)・・・・・・・・・・
...(3), and by eliminating the distance from equations (2) and (3), we obtain. That is, according to equation (4), the surface potential EH2
It can be seen that the output voltages va and Vb of the two detection electrodes can be expressed by a simple equation. Here ale “2ab1*J
are constants, so if the output voltages va and Vb are known, the surface potential E of the object to be measured can be determined regardless of the distance.

For rounding to realize this equation (4), for example, the differential amplification means shown in FIG. 4 may be connected to the uninvented potential sensor.

FIG. 4 is a circuit diagram showing an embodiment of the differential amplifier section in the potential sensor according to the invention. In the same figure, the differential amplification section has each output voltage V from the output terminals 5a, 5b of the sensor section,
General amplifiers 11 and 12 each amplify Vb.

It consists of a general differential amplifier 13 which inputs the output voltages Vl and Vl of the amplifiers 11 and 12 to the -0 signal through resistors R1, respectively, and the output voltage from the output terminal of the differential amplifier 13. vs"t" and take it out.

It is connected to the one terminal via a resistor R2.

In the non-circuit, the output voltage Y1. V2 and resistance ratio R
t/Rz k respectively niroazVB, vz=alV
b> and R1/Rz=alb2-asJ(*daL/”
1m ” L bisb2 is shown in equation (4) and is the following constant)
It is clear that if n is defined as n, the output voltage v3 will indicate the surface potential E of the object to be measured according to the above equation (4).

(Effects of the Invention) As is clear from the above explanation, according to the potential sensor of the present invention, the distance characteristics of the potential sensor can be influenced by connecting the output voltages from the two electrodes to a simple differential amplification means. can be removed, resulting in the effect that the surface potential of the object to be measured can be measured accurately and easily.

[Brief explanation of the drawing]

Figure 1 (a) 2 and ~) is a plan sectional view 2 and a side sectional view showing an example of a conventional potential sensor. Figure 2 shows an example of the distance characteristics of the potential sensor 2 in Figure 1. The characteristic diagrams shown in FIGS. 3(a), 3(b), and 3(c) are a plan sectional view, a side sectional view, a perspective view, and a fourth The figure is a circuit diagram showing an embodiment of the differential amplifier section in the potential sensor of the present invention. In the figure, 1...case, 2...old tuning fork,
2a. 2b... tip, 3.3a, ab...
・Detection electrode, 4... Tuning fork drive terminal, 5s 5
a, 5b... Output terminal, 6... Piezoelectric ceramic is connected, 7... Lines of electric force, 8... Substrate, 9...・Grounding terminal% 1o...Detection hole, 11゜12...Amplifier, 13...
Differential amplifier. Kaya 10 ￥-5 Koki 4-times 2

Claims (1)

[Claims] 1411 A tape collar portion that cuts electric lines of force radiated from a fixed object at a constant cycle, an electrode portion that receives the cutting force N by a chopper portion, the wire collar portion and the electrode portion. The board that carries the and the front aa'! The front electrode portions are arranged on the substrate at different heights from each other in a ``vertical sensor'' which has a detection hole for introducing electric lines of force and a case for accommodating the substrate. Consisting of two magnetic poles
1, and the output magnetic pressure from the top pole is connected to differential amplification means.