JPS61292572A - Static electricity measuring apparatus - Google Patents

Abstract

PURPOSE:To obtain a measuring apparatus with an excellent operability, by driving a rotary sector at a fixed speed with a DC motor while a polarity discriminator is added to a circuit configured section to switch the polarity in a rectifier in order to realize a smaller size, a lighter weight, a higher sensitivity and the like. CONSTITUTION:This measuring apparatus is made up of a mill head 1, a circuit configured section comprising an amplifier 2 for amplifying the output thereof and a rectifier 3, an indicator 4 for display of measured values and a polarity discriminator 5 added thereto. The mill head 1 incorporates a rotary sector 7 and a detection electrode 8 into a cylinder housing 6 sealed, and particularly the sector 7 is driven at a fixed speed with a DC motor with a governor. Then, the use of a peak comparison type of FF type polarity discriminator 5 enables the discrimination of the voltage area or the time area of a signal. The polarity of the rectifier 3 is switched over according to the polarity of the waveform having an excessively jumped peak value detected and the information on the measured value can be obtained by integrating the output waveform thereof.

Description

[Detailed Description of the Invention] <Field of Application of Industry-H> The present invention relates to a one-rotation sector type static electricity meter, and in particular,
This is a means for determining the polarity of electrostatic charge on a charged object, and can be used as a small portable device to detect static electricity on various charged objects. It can be used for air measurement.

<Prior Art> A device called a feed mill, which uses electrical amplification means to improve sensitivity and reading accuracy, is already well known as a static electricity measuring device. In such a device, AC amplification means is employed to stably and highly amplify the detection input. For this purpose, an alternating current means is required to change the detection input periodically.An example of this is a rotating sector electrostatic meter that has a rotating sector that functions as a shutter between the subject and the opposing detection electrode. .

By the way, there are two types of electrostatic fields that remain in the subject: positive electric fields and negative electric fields, and when using the above-mentioned measuring device, it is necessary to perform polarity discrimination. Conventionally, there are the following two methods as means for determining polarity.

That is, one of them is a synchronous detection means using a signal synchronized with the alternating current input from the rotating sector, and the other is a midpoint matching means for applying a constant DC bias to the rotating sector.

<Problems to be Solved by the Invention> In such a conventional device, a synchronous motor is used as a motor for driving the rotating sector in the synchronous detection means, but as long as the synchronous motor is powered by commercial AC, its rotation is Since the number is limited below a certain limit, it is not possible to increase the speed; therefore, the higher the rotational speed of the sector, the more this kind of device has a fully open as well as a fully closed state for the sensing electrode. The greater the number of periodic changes between these, the higher the sensitivity can be. However, if a motor is used for several periods, it is difficult to increase the sensitivity of the device due to the reasons mentioned above.

Moreover, it is impossible to expect the device to be smaller and more portable.

On the other hand, with the center point matching means, it is necessary to adjust the amplification degree of the amplifier so that the pointer of the indicator points to the zero value at the center of the scale using the bias voltage in a non-sensing state each time a measurement is made, which makes the measurement operation troublesome. .

In view of the above-mentioned problems of the conventional device, the present invention aims to provide a rotating sector type electrostatic meter for field mills, which has excellent operability, and which realizes a smaller size, lighter weight, higher sensitivity, and lower cost. It was developed for this purpose.

Means for Solving the Problems> For this purpose, in the present invention, the rotating sector is constructed of a metal disk with a large closed area, and a DC motor is used as a constant speed drive source for the sector. A polarity discriminator consisting of an electronic circuit such as a peak comparison circuit that uses a comparator to determine the signal from a peak detector, or a flip-flop circuit that uses a comparator to determine the signal from a flip-flop circuit that operates via a waveform shaper. is used to measure polarity switching in the rectifier.

In the present invention, which is composed of a rotating sector type electrostatic meter, by rotating a rotating sector located between a charged body to be measured and a detection electrode of the measuring device at a constant speed, direct current from the charged body is removed. The target signal is converted to an AC signal to facilitate amplification, and the output is rectified and read by swinging a DC indicator.

Under this series of actions, according to the above means of the present invention, the periodic information signal generated at the detection electrode during constant speed rotation of the rotating sector with a large closed area has a duty ratio of the waveform having its peak value. can be made smaller, in other words,
Due to the load resistance, the peak value of the waveform with a small duty ratio has a large difference value compared to the peak value of the waveform on the other pole side.

Therefore, by utilizing the characteristics of a signal having a waveform with a different duty ratio and a prominent peak value, it is possible to discriminate the waveform. That is, according to the means of the present invention, by using a peak comparison type polarity discriminator, it is possible to discriminate the signal in the voltage domain, and by using a flip-flop type polarity discriminator, it is possible to discriminate the signal in the voltage domain. Discrimination of signals in the time domain becomes possible.

Measurement value information is obtained by switching the polarity of the rectifier according to the polarity of the waveform with the noticeable peak value that can be determined and integrating the output waveform.

Next, preferred embodiments of the present invention will be described.

<Embodiment> FIG. 1 shows the configuration of an embodiment of the measuring device of the present invention, which includes a mill head l and an amplifier 2 for amplifying the output of the mill head l.
and a rectifier 3, an indicator 4 for displaying measured values, and a polarity discriminator 5 added to the circuit component.

As shown in FIGS. 2 and 3, the mill head l has a rotary sector 7 in a shielded cylindrical housing 6.
In particular, a DC motor 9 with a governor is used as a motor for driving the sector 7 at a constant speed. Furthermore, the relationship between the rotating sector 7 made of a metal plate and the detection electrode 8 is such that the sector 7 is provided with an opening 7a that coincides with the sector-shaped detection electrode 8 arranged at the rear, and is closed to the other closed part 7b. The opening angle (approximately 36°) is made sufficiently small. Note that when considering the dynamic balance of the rotating sector 7, it is also effective to provide a pair of openings 7a at symmetrical positions with respect to the sector rotation axis. On the other hand, the electrical coupling between these is assumed to be an equivalent circuit consisting of a coupling capacitance C and a load resistance R, as shown in Figure @4.

Now, when considering the detection characteristics of this type of rotating sector type measuring device based on the above-mentioned equivalent circuit, first, in principle,
Due to the constant speed rotation of the sector 7, the lines of electric force entering the detection electrode 8 increase or decrease in proportion to the rotation angle of the sector 7, and a certain section where the opening 7a passes directly above the electrode 8 is affected by the previous electric field. Assuming that the lines of force do not change, if the load resistance R is infinite, the detected output waveform will be a unipolar trapezoid as shown in (a) in FIG. When the resistance R is finite and the leakage current between the bonds increases, an exponential decay appears in the flat part of the trapezoidal waveform (with a time constant = RC
), followed by a discharge straight line (lower view (b) in Figure 5),
As a result, this discharge straight line swings to the opposite polarity, and furthermore, the exponential decay of the opposite polarity becomes uniform. When the time constant τ is small, the swing to the opposite polarity becomes large, and the output waveform becomes symmetrical in both positive and negative polarities, and the closing angle in the rotating sector 7 is small, so that the detection electrode 8 is in a closed state. If the rotation period is short, the influence of the voltage will appear in a state where the exponential attenuation in the waveform of the previous cycle is not sufficient, and the output waveform in this case will also approach a positive-negative symmetrical shape. Note that the schematic diagram shown in FIG. 5 above is for a case where the charged body is in a positive electric field, and when it is in a negative electric field, the output waveform has a polarity opposite to that shown in the diagram.

From this, the following can be understood as the characteristics of the detected output waveform in this type of rotating sector type measuring instrument.

a) The output waveforms in the positive and negative electric fields of the charged body differ in the following points.

■In a positive electric field, the positive half wave has a larger peak value than the negative half wave.

In a negative electric field, the negative half-wave has a larger peak value than the positive half-wave.

That is, there are differences in the voltage range of the waveforms.

II For positive electric fields, the positive half-wave precedes the negative half-wave.

In a negative electric field, the negative half-wave precedes the positive half-wave.

That is, there are differences in the time domain of the waveforms.

b) The closed section of the rotating sector with respect to the sensing electrode is short.

In this case, the difference in the previous item (a) disappears in both (1) and (II), and the output waveform approaches a symmetrical shape in both positive and negative poles, and in particular, there is no distinction between the "leading half wave" and the "following half wave."

Under these conditions, in one illustrated embodiment of the invention,
The rotating sector 7 is connected to the closing part B at an opening angle (approximately 3
6°) is made sufficiently small, the waveform (input waveform to the rectifier 3) obtained by amplifying the output of the detection electrode 8 regulated by this by the amplifier 2 is in the state shown in Fig. 6 (compatible with negative electric field). becomes.

Considering the characteristics of this rectifier input waveform, the polarity discriminator 5
First, the peak comparison type circuit configuration shown in FIG. 7 is applied. That is, the waveform from the amplifier 2 is detected by a positive peak detector 10 and a negative peak detector 11 which are made up of ideal diodes constructed by combining a diode and an operational amplifier, and the signal in this state is detected via a resistor adder 12. are compared by a comparator 13, and depending on the state in which the peak value is large, the relay 14 at the subsequent stage is driven to switch the polarity of the rectifier 3. As a result, positive and negative peak values that occur before and after the waveform can be temporarily stored in the re-detectors 10 and 11 and can be discriminated in the voltage region of the waveform.

Next, based on the difference in the time domain of the waveforms, a flip-flow or flip-type circuit configuration can be applied as the polarity discriminator 5. Its configuration is shown in FIG. Between the cores, 15 and lθ are a positive half-wave waveform shaper and a negative half-wave shaper consisting of a comparator configuration, and 17 and 18 are a positive floating reference voltage generator and a negative floating reference voltage generator consisting of a peak detector configuration. 9, the waveform from the amplifier 2 is passed through the floating reference voltage generator 17 and the waveform shaper 15 which receives the reference voltage of both poles (see FIG. 9). and 16, as shown in the figure, logic L (Glanton) in the waveform range exceeding the voltage level.

In other regions, it becomes a pulsed signal that becomes H (power supply voltage) and is applied to the set terminal S, the reset terminal R of the flip-flop circuit 19, respectively. When the flip-flop circuit 19 receives a logic logic at its terminal S, its output Q
becomes H, and the output Q becomes L and is fixed. After that, no matter what input is applied to the terminal S, this state will not change. Also, if a logic logic is applied to the terminal R, the output Q becomes H. It becomes fixed. Therefore, using the value obtained by averaging the output 4 by the integrator 20 (see the figure), the comparator 13 can make a determination in the same manner as described above, and the relay 14 can be controlled.

That is, to explain the outline of this operation based on FIG. 9, the outputs of both waveform shapers 15 and 1B are in the H state most of the time, and the absolute value of the input voltage is equal to the absolute value of the reference voltage. As a result, the difference between the positive electric field and the negative electric field in the waveform is the difference in which of the outputs of the waveform shapers 15 and 16 becomes L first. Become. Therefore, the output point of the flip-flop circuit 19 that receives this is H for most of the time in the case of a positive electric field, and L for most of the time in the case of a negative electric field. This determination can be made by averaging the values and inputting them into the comparator 13 at the subsequent stage.

In addition, since the comparator 13 in this case discriminates between the average value H and the average value, whereas the reference voltage in the case of the peak comparison type was basically zero,
In this case, the voltage is, in principle, half the power supply voltage.

Further, while the peak comparison type mentioned above is affected by the offset e drift of the amplifier etc., this flip-flop type does not have this concern.

By the way, if we look only at the operation diagram shown in FIG. 9, in this flip-flop type circuit configuration, the duty ratio of output 4 approaches 1/2 as the input signal becomes larger, and the positive electric field of the charged body and the negative electric field There is a concern that the difference between the electric field and the electric field will disappear. Therefore, in this circuit configuration, in particular, the positive and negative floating reference voltage generators 17 and 18
The input signal is peak-detected using these devices, and the output is voltage-divided and used as a reference voltage for the comparators serving as both waveform shapers 15 and 16. By changing the polarity according to the input signal, The structure is such that the stability of the discrimination is independent of the input signal level.

Note that the larger the reference voltage is (the closer it is to the peak value of the input signal), the later the start point of output Q (for example, the point at which output Q changes from H to L in the case of a positive electric field), and the output Q and output will be delayed. The difference from Q becomes larger and easier to distinguish, and conversely, the lower the voltage, the more the output Q ends (if the electric field is positive, the output ζ
It is preferable that the voltage changes from H to L quickly, but if the voltage is too low, there is a risk of malfunction due to noise, so the voltage should be set at 50 to 80% of the peak value of the input signal.
The degree is appropriate.

<Effects of the Invention> As described above, according to the measuring device of the present invention, the rotating sector is constituted by a metal disk with a large closed area, a DC motor is used as a constant speed drive source of the sector, and the signal from the peak detector is The polarity in the rectifier is determined using a polarity discriminator consisting of an electronic circuit such as a peak comparison circuit that is determined by a comparator or a flip-flop circuit that determines the signal from a flip-flop circuit that operates via a waveform shaper. By using a polarity discriminator consisting of an electronic circuit, it is possible to use a DC motor to drive the rotating sector instead of using a synchronous motor, thereby reducing the size and weight of the mill head. This makes it possible to control the high-speed rotation of the sector, which makes it easy to increase the sensitivity of the device, and because it can be powered by a battery, it can be configured as a portable device, and the entire device is low-cost. In particular, when a time-domain discriminator circuit means is employed as a polarity discriminator, it is possible to use an amplifier with low input impedance, so it is more stable. The measuring device of the present invention is extremely useful in practice as a device of this type.

[Brief explanation of drawings]

Fig. 1 is a basic configuration diagram of the measuring device of the present invention, Fig. 2 is a side view partially showing the mill head in the measuring device of the present invention, Fig. 3 is a front view, and Fig. 4 is the mill head. 5 is a schematic diagram of its output waveform, FIG. 6 is an amplifier output waveform diagram in the measuring device of the present invention, and FIG. 7 is a configuration diagram showing an example of a polarity discriminator in the measuring device of the present invention. FIG. 8 is a block diagram showing another example of the polarity discriminator in the measuring device of the present invention, and FIG. 9 is an explanatory diagram of the operation in the example not shown in FIG. Engineering...mill head, 2...amplifier, 3...rectifier, 4...
-Indicator, 5...Polarity discriminator, 7...Rotating sector, 7
a...Opening part, 7b...Closing part, 8-φ detection electrode, 9-
・DC motor. Figure 1 Figure 2 Figure 3

Claims (3)

[Claims] (1) It consists of a mill head consisting of a rotating sector and a detection electrode, a circuit component consisting of an amplifier and a rectifier etc. that amplify the output of the mill head, and an indicator for displaying measured values, and the rotating sector is connected to a closed area. It is constructed of a large metal disk and is driven at a constant speed by a DC motor, and a polarity discriminator based on waveform signals with different duty ratios of the output is added to the circuit component to measure polarity switching in the rectifier. A static electricity measuring instrument characterized by the following configuration. (2) The static electricity measuring instrument according to claim 1, wherein the polarity discriminator is constituted by a peak comparison type circuit that discriminates the signal from the peak detector using a comparator. (3) The static electricity measuring device according to claim 1, wherein the polarity discriminator is constituted by a flip-flop circuit that uses a comparator to discriminate a signal from a flip-flop circuit that operates via a waveform shaper. .