Electrostatic meter

An apparatus for detecting and measuring disturbances in an electromagnetic field caused by the electrostatic potential of a charged object moving the field includes a DC source, a loop/solenoid coil, and a metering unit. The DC source charges the loop/solenoid coil, and thereby creates the electromagnetic field that emanates from the coil. The metering unit is provided to (indirectly) sense and quantify the disturbances in the electromagnetic field of the loop/solenoid coil by indicating a change in a current flow through the coil. The apparatus may be configured with a housing to enclose a plurality of components of the apparatus including the DC source, the loop/solenoid coil, and the metering unit.

CROSS REFERENCES 
This Application relates to subject matter filed in the United States 
Patent and Trademark Office on Jul. 13, 1995, in provisional application 
Ser. No. 60/001,119. 
BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to educational scientific devices, and more 
particularly, the invention relates to a simple, portable, and 
selfcontained demonstration system for detecting and measuring 
disturbances in electromagnetic fields caused by the electrostatic 
potential of electrically charged objects, including humans. 
2. Background and Objects of the Invention 
The fundamental concepts and theories of basic electricity and magnetism 
are well know in the art. Many inventors and scientists are responsible 
for the established art that is employed by electronic systems and 
instruments in operation today. These fundamental concepts and laws, which 
must be studied by persons wishing to learn and understand electricity and 
electronics, include work by Benjamin Franklin (1706-1790) who first 
proposed the existence of positive and negative charges and discovered the 
relationship between electrostatic force and conducting (lightning) rods, 
Alessandro Volta (1745-1827) who invented the "voltaic pile" (i.e. the DC 
battery), and Andre Ampere (1775-1836) who discovered magnetic fields were 
created in and around conductive wires connected across DC cells. These 
fundamental phenomenon and concepts, as well as others discovered by 
Faraday, Henry, Hertz, Coulomb, Maxwell, and others, are typically studied 
and utilized by students of electricity and electronics. 
The use of educational devices to demonstrate electrical and electronic 
principles is also well known in the art. However, due to the "invisible" 
nature in which electrical and electronic devices implement their 
functions, it is difficult to demonstrate and discuss the underlying 
principles of such devices and systems, especially to young and novice 
individuals wherein the discussion must be limited in complexity. In order 
to educate such young and novice individuals, educational systems that 
provide for an interactive discussion and demonstration, possibly having a 
"gee-whiz" nature, are desired. For example, employing simple arrangements 
such as magnets and iron filings to discuss and demonstrate the existence 
of magnetic poles and fields, is a well established practice that grabs 
and interests a young audience. As another example, consider the use of an 
iron rod, an insulated coil of wire disposed around the iron rod, and a DC 
source (i.e. a battery) to create an electromagnet. It may be noted that 
this is not only an effective educational or teaching device, but is a 
"practical" arrangement employed in components of many commercial systems 
in use around the world. The need for devices to enable interesting 
interactive discussions and demonstrations is essential to the education 
of persons unfamiliar with the concepts and laws that govern basic 
electricity and electronics. 
The field of electrostatics and charged particles is another area of 
electricity and electronics that may employ demonstration devices to 
introduce fundamental concepts and laws. One area not easily presented and 
discussed via demonstrations is that involving the use of charged 
loop/solenoid coils and their interaction with electrostatic charge. In 
particular, the use of a charged loop/solenoid coil to establish an 
electromagnetic field, and subsequently sensing and measuring disturbances 
produced by the electrostatic potential of electrically charged objects in 
motion or placed within the field, is desired. Accordingly, such devices 
should be able to grab the attention of an audience and enable a science 
educator to discuss and demonstrate the important properties to be 
examined. 
Objects of the present invention are, therefore, to provide a new and 
improved scientific educational system for demonstrating the principles of 
charged loop/solenoid coils. The present invention having one or more of 
the following capabilities, features, and/or characteristics: 
a portable self-contained demonstration system; 
an educational device that may be employed to introduce the concepts and 
principles related to charged loop/solenoid coils and their relationship 
to electrostatic charge; 
a system capable of sensing and measuring of the disturbances on an 
electromagnetic field induced by the electrostatic potential of 
electrically charged objects moving or placed within a region occupied by 
the field; 
having a direct "readout" device to indicate the magnitude of the 
disturbances on the electromagnetic field; 
constructed of simple and inexpensive off the shelf components. 
The above listed objects, advantages, and associated novel features of the 
present invention will become more clear from the description and figures 
provided herein. Attention is called to the fact, however, that the 
drawings are illustrative only. Variations are contemplated as being part 
of the invention, limited only by the scope of the appended claims. 
SUMMARY OF THE INVENTION 
In accordance with the invention, an apparatus is disclosed for detecting 
and measuring disturbances in an electromagnetic field caused by an 
electrostatic potential of one or more electrically charged objects placed 
within, or moving within, a region occupied by said field. The apparatus 
includes a DC source having a positive terminal and a negative terminal 
and capable of supplying a DC power. A loop/solenoid coil is provided 
having a first terminal and a second terminal, and formed from an 
insulated conductor appropriately shaped to provide a plurality adjacently 
positioned coils of insulated wire. The loop/solenoid coil is connected 
across the DC source with the positive terminal of the DC source connected 
to the first terminal of the loop/solenoid coil, and the negative terminal 
of the DC source connected to the second terminal. Thereby placing a DC 
potential produced by the DC source across the loop/solenoid coil to 
charge and establish an electromagnetic field within the region that 
surrounds the coil. Also provided is a metering unit capable of sensing 
low level DC currents. The metering unit has a first terminal means that 
is connected to the positive terminal of the DC source and a second 
terminal means that is connected to the negative terminal. The metering 
unit is provided to detect and measure disturbances in the electromagnetic 
field of the loop/solenoid coil by indicating a change in a current flow 
through the coil. 
The apparatus of the present invention may further include a housing to 
enclose a plurality of components of the apparatus including the DC 
source, the loop/solenoid coil, and the metering unit. The housing is 
comprised of a first shell portion composed of a transparent material and 
a second shell portion arranged to mate with the first shell portion. 
Together, when mated, the first and second shell portions establish an 
interior chamber. A support plate suitably positioned within the interior 
chamber is arranged to support a plurality of the components of the 
invention including the DC source and the metering unit. The metering unit 
is suitably supported by the support plate so as to enable the viewing of 
the metering unit (readout) through the transparent first shell portion. A 
base is also included to support the housing in a fixed orientation with 
respect to a supporting surface.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the context of this disclosure a number of terms must be clearly 
defined. First, it should be understood that the term "region" as applied 
to the area around a loop/solenoid coil, is to be defined as the immediate 
area that surrounds the coil and is occupied by an electromagnetic field 
established by charging the coil. The terms "educational demonstration 
device" and "educational system" may be assumed to be equivalents. 
Further, the terms "loop/solenoid coil" and "coil" are to be assumed to 
mean an inductive component constructed by forming a plurality of loops 
using an insulated wire, the loops being adjacently positioned in very 
close proximity and substantially aligned along a single given axis. 
Referring now to FIGS. 1 and 2, there is illustrated an embodiment of an 
electrostatic meter 10 configured in accordance with the present 
invention. As shown, the electrostatic meter 10 includes a metering unit 
12, with a loop/solenoid coil 20 and a DC source 38, all of which are 
electrically connected in parallel. The DC source 38, having a positive 
terminal 38a and a negative terminal 38b, will provide a power source to 
establish a "minute pressure" (i.e. a small voltage) across the 
loop/solenoid coil 20 (and the metering unit 38). The loop/solenoid coil 
20 includes a first terminal 20a and a second terminal 20b, and is 
produced from a length of insulated conductive wire, preferably composed 
of copper, forming a plurality adjacently positioned coils (of the 
insulated wire), with the centers of the loops approximately concentricity 
aligned along a single axis. The loop/solenoid coil 20 is electrically 
connected across the DC source 38 with the positive terminal 38a of the DC 
source connected to the first terminal 20a of the loop/solenoid coil 20, 
and the negative terminal 38b of the DC source 38 connected to the second 
terminal 20b (of the coil 20). Therefore, inducing a DC potential across 
the loop/solenoid coil 20, and is essentially applying a "bias" to charge 
the coil 20. It may be noted that the coil 20 does not have a polarity 
associated therewith, and accordingly may be connected as shown in FIG. 1, 
or alternately with the first terminal 20a and the second terminal 20b 
"reversed" . (That is, with an orientation wherein the first terminal 20a 
is connected to the negative terminal 38b of the DC source 38.) The bias 
(pressure) applied to the coil 20 will cause an electromagnetic field to 
be produced by charging the coil 20. The electromagnetic field established 
by the coil 20 will provide a sensitivity to, and enable the detection of, 
nearby electrically (or electrostatically) charged objects that are within 
the region the electromagnetic field occupies. Essentially, the 
loop/solenoid coil will act as an "antenna" and detect the electromagnetic 
field disturbances. The loop/solenoid coil 20 would be constructed to have 
a suitable number of "loops" , formed with an appropriate gauge conductive 
wire, in order to provide an adequate resistance to prevent an excessive 
current to flow through the coil 20 when the DC source 38 is connected in 
parallel. In addition, the number of loops provided with the coil 20 will 
also affect the sensitivity of the present invention when detecting 
electrostatically charged objects. The metering unit 12, which is capable 
of sensing "low level" DC currents, is provided to detect and quantify 
(measure) disturbances in the electromagnetic field of the coil 20 by 
indicating a change in the current flow through the coil 20. It in 
important to note that since the metering unit 12 and the loop/solenoid 
coil 20 are connected in parallel, should the current flowing through the 
coil 20 decrease, the current indicated by the metering unit 12 would 
increase. Accordingly, when an electrostatically charged object is placed 
within, or moves within, the region (occupied by the electromagnetic field 
of the coil 20), the electromagnetic field is disturbed, resulting in a 
deviation of the constant current flowing through the coil 20. This 
deviation would be detected by the metering unit 12. The term low level DC 
currents may be assumed to indicate electrical currents in the range of 0 
to 1 microamperes. Therefore, the metering unit 12 may be provided by a 1 
microampere meter movement. 
Also shown in FIG. 1 is a DC recharging circuit 58, which may be included 
with electrostatic meter 10 when the DC source 38 is provided by a 
rechargeable battery, preferably a Ni-Cad type of battery. Since the 
electrostatic meter 10 is contemplated to be a portable and self contained 
unit, the use of one of more rechargeable battery cells will mean that the 
meter 10 may be "recharged" when not being used. 
A housing is included with the electrostatic meter 10 to enclose a 
plurality of the components of the electrostatic meter 10 (including the 
loop/solenoid coil 20, the DC source 38, and the metering unit 12) as 
illustrated in FIGS. 1 and 2. The Housing is comprised of a first shell 
portion 14a and a second shell portion 14b. When properly mated, as shown, 
the first shell portion 14a and second shell portion 14b establish an 
interior chamber 15. The housing further includes a support plate 14c, a 
support means 18a and a base 18b. The support plate 14c is included and 
suitably positioned within the interior chamber 15, and arranged to 
support the plurality of components of the invention. The support plate 
may be fixed (as shown in FIG. 1) to the second shell portion 14b in any 
suitable manner, including a "press fit" or by using a suitable glue. In a 
preferred embodiment the support plate 14c will be provided by a mirrored 
plastic disk, the first shell portion would be provide by a transparent 
material, and the second shell portion would be provided by an opaque 
(e.g. silver colored) material. Also shown in FIGS. 1 and 2 are fastening 
means 14d including tabs 14e, which are provided to secure the first shell 
portion 14a to the second shell portion 14b. As skilled individuals will 
appreciate, many differing fastening means 14d may be employed with the 
present invention. 
Returning to FIG. 1, the first and second shell portions, 14a and 14b 
respectively, are supported by support means 18a and base 18b. In a 
preferred embodiment the support means 18a would be provided by a 
cylindrical tube of suitable diameter, having the opposite side walls cut 
out or removed (as shown in FIG. 1), and fixed to the second shell 
portion-14b. The base 18b may be fixed to the support means 18a, or 
preferably the base may include a circular groove or channel (not shown) 
that would enable the support means 18a to mate with the channel and 
thereby provide a simple arrangement to enable the rotation of the upper 
housing portion (comprised of the first shell portion 14a, the second 
shell portion 14b, and the support means 18a) with respect to the base 18. 
As shown in FIG. 1 a compass 54, which may be mounted concentricity on the 
base, is included to enable the electrostatic meter 10, and in particular 
the loop/solenoid coil 20, to be oriented with respect to the magnetic 
north pole of the earth. For example, if an operator of the electrostatic 
meter 10 desired to align the meter 10 or the coil 20 with a (true) 
north-south orientation, the upper housing S portion may be rotated (with 
respect to the base 18b) until the desired orientation is realized. 
It should be noted that the embodiment of FIGS. 1 and 2 is intended to be 
illustrative only. For example, variations to the shape of the housing and 
the material utilized to construct it are contemplated, and may be 
provided by skilled persons. 
Referring now to FIGS. 3 and 4, there are illustrated a block diagram and 
schematic diagram of the present invention, respectively. As shown, the 
electrostatic meter 10 is comprised of the loop/solenoid coil 20, the 
metering unit 12, and the DC source 38, and may further include the DC 
source recharging circuit 56. As discussed herein, and illustrated in FIG. 
4, the coil 20, the metering unit 12, and the DC source 38 are connected 
in a parallel arrangement. However, as illustrated in FIG. 4, an on-off 
switch 60 may also be included to enable an individual to selectively 
connect and disconnect the DC source 38 and the parallel combination of 
the metering unit 12 and the coil 20--thereby providing an "on-off 
switch". Also shown in FIGS. 3 and 4, is the DC source recharging unit 56, 
which may be included with the electrostatic meter 10 if the DC source 38 
is provided by a suitable rechargeable battery, preferably a Ni-Cad type 
battery. An external power source 58 may be electrically coupled to the 
recharging unit 56 to supply an external source of power for recharging a 
rechargeable embodiment of the DC source 38. 
While there have been described the currently preferred embodiments of the 
present invention, those skilled in the art will recognize that other and 
further modifications may be made without departing from the present 
invention and it is intended to claim all modifications and variations as 
fall within the scope of the invention.