APPARATUS FOR MEASURING THE ELECTRIC POTENTIAL OF AN ELECTROSTATIC FIELD

Abstract: An apparatus for measuring an electric potential in an electrostatic field comprises (a) sensor means (1) including a pair of electrodes (E1, E2) opposing each other with a gap therebetween and chargeable by electrostatic induction; and (b) circuit means (2) for detecting and indicating occurrence of a discharge across the gap between the pair of electrodes.

Description: APPARATUS FOR MEASURING THE ELECTRIC POTENTIAL OF AN ELECTROSTATIC FIELD The present invention relates to an apparatus for measuring the electric potential of an electrostatic rielc. Various measuring instruments have conven- tionally been developed for measuring the intensity c, electrostatic field in terms of quantities of electric charge, such as Z series of detectors, e.g., Kolbe charge electrostatic meter, Brawn electro potentio meter, Wilson charge quantity meter, etc., (versorium-type charge quantity meters) and rotary-sector-type electric potential measuring instruments using an electrostatic induction phenomenon. However, there are various disadvantages in such rneasuring instruments in that the former instruments are insufficiently accurate in terms of quantitative measurements and the latter instruments are complex in structure and cannot also make an accurate measurement in cases where the electrostatic field is anisotropic although the accurate measurement can be mace in cases where tne electrostatic field is isotropic. With the above- escribed matters in mind, it is an object of the present invention to provide an apparatus, for measuring the electric potential of an electrostatic fiela which has G simple structure and can accurately measure the electric potential at any point ot the electrostatic field regardless of whether it is isotropic or anisotropic in the distribution or electric charge. To achieve the present invention, an apparatus far measuring the electric potential of an electrostatic <RTI ID=2.11> rigid comprises: (a) sensor means (1) including a pair of electrodes (El, E2) opposing each other with a gap (G) therebetween and chargeable by electrostatic ir,duction; and (b) circuit means (2) for detecting and indicating occurrence of a discharge across the gap (G) between the electrodes. Ways of carrying out the invention are described in detail below with reference to drawings which illustrate two specific embodiments. In the attached drawings in which like reference numerals designate corresponding elements: Fig. 1 is a block diagram of a first preferred embodiment of an apparatus for measuring the electric potential of an electrostatic field according to the present invention; Fig. 2 is z block diagram of a second preferred embociment according to the present invention; ana Figs. 3(A) and 3(B) show other examples or. application of the apparata shown in Figs. 1 and 2 to measurement of the electrical potential of an electrostatic field. Ref erring now to the drawings in which, Fig. 1 shows a first preferred embodiment according to the present invention. In Fig. 1, symbol El denotes a first electrode, E2 denotes a second electrode opposing to the first electrode El and which is grounded, SI denotes an insulating support, and G denotes a discharge gap between the first and second electrodes El and E2. These elements form a sensing section 1 portable to any point of measurement. It should be noted that, in this embodiment, an appropriate adhesive is used to fix both the electrodes El and E2 to the insulating support SI. Alternatively, the first electrode El may be adjustable positioned, e.g., engaging a guide groove (not shown) provided within the insulating support SI so as to allow adjustment of the discharge gap G when a lock screw (not shown) in the insulating support SI and in engagement with the first electrode El via the guide groove is loosened from the first electrode El, with the grounded second electrode E2 fixed to the insulating support SI. In this case, the first electrode El is fixed to the insulating support SI so that the discharge gap G is fixed. Alternatively, the grounded second electrode E2 may be adjustable with the first electrode El fixed to the insulating support SI or both electrodes El, E2 may adjustable. In addition, in Fig. 1 symbol A denotes a stroll telescoping antenna or loop-type antenna capable of receiving wide frequency band of the electromagnetic spectrum, RM denotes an antenna biasing resistor, PI denotes polarity inverter, OR denotes an OR gate c.rcuit, Co denotes a comparator, Es denotes a terminal of the comparator CO to which a reference voltage is applied, TM denotes a timer, e.g., monostable multivibrator, FF denotes a flip-flop circuit, ES denotes z self-returning manual reset switch, DR denotes a drive circuit, and LED denotes a light-emitting diode. These elements form a discharge detection circuit 2, which may be separate from the sensIng section 1. In the apparatus shown in Fig. 1, when the rlip- flop circuit FF is reset once with the reset switch ES to turn on and the first electrode El is placed within the electrcsta.ic field to be measured, an electric charge cf a magnitude related to the intensity of the electrostatic field to be measured is built up by electrostatic induction over the first electrode El. It should be noted that aster resetting the flip-flop circuit FF, the potential of a reset terminal R thereof is zerc. When the magnitude or the electric charge exceeds z certain quantity derived from Paschen's law, an gaseous discharge is generated across the discharge gap G. When the gaseous discharge is generated, an electric voltage of a polarity determined by the direction of the discharge current is induced in the antenna A of the discharge detection circuit 2. The voltage induced in the antenna A is applied to the comparator CO either via the polarity inverter PI and OR gate circuit OR or via the OR gate circuit OR alone depending on the polarity of the induced voltage. If the voltage applied to the comparator CO is higher than the reference voltage Ref applied via the terminal Es, the output voltage of the comparator CO goes high so that the flip-flop circuit FF is set via the timer TN. The set voltage from the flip-flop circuit FF is, in turn, applied to the drive circuit DR so that the light emitting diode LED emits light to indicate that the gaseous discharge has been generated across the gap G. Consequently, if the length of the gap G is known, the point within the electrostatic field at which the correspond break-Gown voltage obtains can be located. It should be noted that the distance between the electrodes El and E2 and antenna A only effects measurement sensitivity but does not effect potential measure.m.er.t values. It should also be noted that since the reference voltage rover applied to the comparator CO is provided so as to prevent the lisht-emittins diode bED from lighting erroneously due to noise, the m snitu¯e of the reference voltage :rtav be determined to be any arbitrary value. In this way, if various insulating support structures wherein the lengths of the gap G differ from each other are prepared, the electric potential at any desired point of measurement can be measured. In addition, if the insulating support is so designed that the length of the gap G can be continuously adjusted, the electric potential at arbitrary measurement points can be measured 'from the instantaneous length of the gap G when the gaseous discharge occurs. In the embodiment shown Fig. 1, the lisht- emitting diode LED serves to indicate that the gaseous discharge has been generated. In place of the lightemitting diode, other indicating means such as a buzzer 3U shown in phantom lines of Fig. 1 may be used. In addition, any suitably sensitive circuit may be used in place of the discharge detection circuit 2 shown in Fig. 1. materials used for the first and second electrodes El and E2 and insulating support SI, their shapes, and the manner in which the first and second electrodes El and E2 are supported on the insulating support SI need not be limited as long as the electrodes El and E2 can be charged (electrified) by electrostatic induction so as to generate the gaseous discharge across the gap thereof. It <RTI ID=6.33> should be noted that if the discharge area of the 2bove-¯escrihed first electrode El is smaller than the opposing second electrode E2 within a range or. proportion at which the corona discharge will not occur across the gap G, the electric potential can be measured with even greater resolution. Fig. 2 shows second prererred embodiment according to the present inventicn. As appreciated from Fig. 2, the construction of the discharge detection circuit 2 is the same as in the first embodiment shown in Fig. 1. However, since the electric potential sensor means 1 is different from that shown in Fig. 1, the electric potential sensor means 1 of the second preferred embodiment will be described hereinafter. As shown in Fig. 2, the electric potential sensor means 1 in this embodiment includes a g2s-filie discharge tube GDT, one of discharge electrodes thereof being connected to the first electrode El and the other discharge electrode being connected to the second electrode E2. The gas-filled discharge tube GDT is fixed to the insulating support SI together with the first and second electrodes El and E2 by means of, e.g., an appropriate adhesive. In Fig. 2, when the insulating support SI, in which the first and second electrodes El and E2 and gcs- filled discharge tube CDT are incorporated, is moved to an crkitrary point of either a irect-current electric yield or 21te,r.zt na-clrrent electric field to be measured after the flip-flop circuIt FF is reset by means of the reset switch RS, an electric charge appears on the first electrode El due to electrostatic induction, the magnitude OL which is related to the electric potential to be measured. If the electric charge exceeds a predeterr#inec value, the gas-fille discharge tube CDT discharges and an electric voltage is induced in the antenna A the polarity of which is determined by the direction of the ctischarge current. The induced voltage is applied to the OR gate circuit OR either directly or via the polarity inverting circuit PI depending on the polarity of the induced voltage, i.e., of the discharge current. The comparator CO compares the output voltage of the OR gate circuit OR with the reference voltage applied at the terminal Es. When the output voltage of the OR gate circuit OR exceeds the reference voltage in the comparator CO, the comparator CO outputs a high-level voltage signal to the timer TM which receives the hish-level voltage signal and outputs a highlevel voltage sIgnal for a predetermined interval of time to set the flip-flop circuit FF. Therefore, the output of the flip-flop circuit FF actuates the drive circuit DR to illuminate the light emitting diode LED in the same manner as described in the first preferred embodiment It should be noted that since the predetermined value of the magnitude of electric charge described above, i.e., break-down voltage of the gas-filled discharge tube GDT is dependent on the shapes of the discharge electrodes, the ischcrge gap length, the kind of gas filling the discharge tube GDT and the pressure thereof, the break-down voltage o# the g2s-filled discharge tube GDT is know, and so when the illumination of the light-emitting cloce #ED signals discharge of the sas-filles discharge tube GDT, the electric field at the point of measurement is known to be at the known break-down voltage, at least. In this embodiment, if a number of the sensors 1 shown in Fig. 2 of differing break-down discharge voltages, are prepared, the electric potential at any point of measurement in the electric field can be measured. In this case, any or all of the parameters determining the breakdown voltage, i.e., the shape of the discharge electrodes, the discharge gap length, the kind gas filling the g2s- filled discharge tube GDT, and the pressure in the gasfilled discharge tube GDT, etc. may differ from one another. Alternatively, it is also possible to use z single sensor means of the type wherein gas-fille discharge tubes GDT differing breck-down voltages can removably be interposed between the corniron first and second electrodes El and E2. Furthermore, although Fig. 2 shows the case wherein the second electrode E2 is grounded, it is also possible to ground the first electrode El in place or the second electrode E2. In addition, if both first and second electrodes float with respect to ground as shown in FIgs. 3(A) and 3(3), the apparatus according to the present invention can measure the potential difference between any two points in the electric field As described in the first embodir1ent with reverence to Fig. 1, the materials, shapes, ano manner or support of the first and second electrodes El and E2 on the insulating support SI may be selected arbitrarily as long as the first and second electrodes El and E2 can be charged by electrostatic induction so as to generate a discharge across the discharge gap of the gas-tilled discharge tube GDT. The size, i.e., the cross-section of discharge of the discharge electrodes of the ses-Elilec discharge tube GDT may be reduced to within a range in which corona discharge will not occur. In this case, the electric potential can be measured with high resolution. Since, in the second preferred embodiment, the small gas discharge tube is interposed between the first and second electrodes, it is possible to obtain 2 precise measurement of a lower electric potential than in the case when a gaseous discharge is generated through the atmosphere between the charged electrodes as shown in Fig. 1. As described above, the apparatus for measuring the electric potential of an electrostatic field according to the present invention constructed as shown in the drawings can make accurate quantitative measurements ct spatial electric potential and the electric potential or charged bodies.

Claims: CLAI !15 1. An apparatus for measuring an electric potential of an electrostatic field, characterized in that said apparatus comprises: (a) sensor means (1) including a pair of electrodes (El, E2) opposing each other with a gap (G,), therebetween and chargeable by electrostatic induction; and (b) circuit means (2) for detecting and indicating occurrence of a discharge across said gap (G) between said pair of electrodes. 2. An apparatus as set forth in claim 1, characterized in that either one of said pair of electrodes (El, E2) is grounded. 3. An apparatus as Set forth in claim 1 or 2, characterized in that said sensor means (1) comprises a sensor structure in which a inter-electrode length of said gap (G) is continuously adjustable. 4. An apparatus as set forth in claim 1 or 2, characterized in that said sensor means (1) comprises 2 plurality of sensor structures each having one of mutually different inter-electrode lengths of said gap. 5. An apparatus as set forth in any of preceding claims, characterized in that the discharge area of either or both of said pair of electrodes (El, E2) falls within a Size range in which corona discharge will not occur across said gap (G). 6. An apparatus as set forth in any of preceding claims, characterized in that said circuit means (2) is located remotely from said sensor means (1). -An apparatus as set worth in any preceding claim, characterized in that said circuit means (2) comprises: (a) a discharge current receiving section (A, RN) for receiving an electromagnetic radiation generated when the discharge is generated across said gap and generating a voltage with 2 polarity corresponding to that of the discharge current across said gap; (b) 2 comparison section (PI, OR, CO) for comparing the voltage generated at said discharge current receiving section with â reference voltage (Ref) and outputting a voltage si5nci when the voltage generated at said discharge current receiving section exceeds said reference voltage; and (e) an indicating section (TM, FF, RS, DR, LED) for indicating that the discharge is generated across said gap when the output voltage is received from said comparator section. 8. An apparatus as set forth in claim 7, characterized in that said discharge current receiving section (A, RN) includes 2 telescoping antenna. 9. An apparatus as set forth in claim 7, characterized in that said discharge current receiving section tA, RN) includes a loop antenna. 10. An apparatus as set forth in claim 71 8 or '9, characterized in that said indicating section includes a light emitting diode (LED). 11. An apparatus as set forth in claim 7, 8 or 9, characterized in that said indicating section includes a buzzer (BU). 12. An apparatus as set forth in claim 1, characterized in that gas-f illed discharge tube (GUT) is interposed between said electrodes (El, E2). 13. An apparatus as set forth in claim 12, characterized in that said sensor means (1) comprises a sensor structure in which any one of a plurality of gasfilled discharge tubes (GDT) having mutually different predetermined break- own voltages is freely inserted and removed from between said pair of electrodes (El, E2). 14. An apparatus as set forth in claim 12, characterized in that said sensor means (1) comprises a plurality of sensor structures in each of which one of a plurality gas-filled discharge tubes (GDT) having mutually different predetermined break-down voltages is fixed to said pair of electrodes (El, E2).

Inventors: KANEKO, YOSHIAKI, KAWAMURA, TAKEYOSHI
Applicants: SANKI ELECTRONIC INDUSTRY
Application year: 1984
Main classification: G01R13
IPC codes: G01R29, G01R13