U.S. patent application number 15/247971 was filed with the patent office on 2017-11-30 for hand-held voltmeter for electric fence.
The applicant listed for this patent is Byung-Hak Cho. Invention is credited to Byung-Hak Cho.
Application Number | 20170343590 15/247971 |
Document ID | / |
Family ID | 58497927 |
Filed Date | 2017-11-30 |
United States Patent
Application |
20170343590 |
Kind Code |
A1 |
Cho; Byung-Hak |
November 30, 2017 |
Hand-held Voltmeter for Electric Fence
Abstract
The present disclosure relates to a hand-held voltmeter
measuring a peak voltage of a high voltage pulse applied to an
electric fence. The voltmeter includes a body case of which one
side has an opening, a sensor case protruded from the opening of
the body case, a voltage divider disposed over the inside and the
outside of the sensor case for dividing the high voltage pulse into
a low divided voltage, a peak detector for detecting the peak
voltage of the divided voltage, a display unit for displaying the
peak voltage, and an MCU for controlling the input and the output
of the elements constituting the voltmeter. According to the
present disclosure, an electric fence voltmeter that measures the
peak voltage accurately without need to make a ground connection to
the earth, and has a low risk of an electric shock during a
measurement is provided.
Inventors: |
Cho; Byung-Hak; (Daejeon,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Cho; Byung-Hak |
Daejeon |
|
KR |
|
|
Family ID: |
58497927 |
Appl. No.: |
15/247971 |
Filed: |
August 26, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01R 19/04 20130101;
G01R 1/06788 20130101; G01R 19/0084 20130101 |
International
Class: |
G01R 19/04 20060101
G01R019/04; G01R 13/00 20060101 G01R013/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 25, 2016 |
KR |
10-2016-0063810 |
Claims
1. An electric fence voltmeter, comprising: a body case (60) of
which one side has an opening: a sensor case (61) connected to the
opening of the body case (60) to protrude from the body case (60):
a voltage divider (10) disposed over the inside and the outside of
the sensor case (61) for dividing the high voltage pulse (Vp)
applied to a probe (11) into a low divided voltage (V2); a peak
detector (20) for detecting the peak voltage of the divided voltage
(V2); a display unit (40) for displaying the peak voltage: and an
MCU (micro controller unit) (30) for controlling the input and the
output of the elements constituting the voltmeter.
2. The electric fence voltmeter of claim 1, wherein the voltage
divider (10) is a capacitor voltage divider composed of a capacitor
(C1) of which the first electrode (C1a) is connected to a probe
(11), and a capacitor (C2) of which one electrode is connected to
the second electrode (C1b) of the capacitor (C1) and the other
electrode is connected to a ground (P2).
3. The electric fence voltmeter of claim 2, wherein the first
electrode (C1a) of the capacitor (C1) is placed on the outer end of
the sensor case (61) in the form of a surface electrode, and the
second electrode (C1b) is placed in the inside of the sensor case
(61) in the form of a surface electrode that is spaced oppositely
to the first electrode (C1a) at a predetermined gap.
4. The electric fence voltmeter of claim 3, further comprising: a
bolt shaped capacitance adjuster (12) made of a conductive material
screwed through a hole formed at the center of the first electrode
(C1a) of the capacitor (C1) into a threaded blind hole (61b) formed
inside of the sensor case (61) directed to the second electrode
(C1b); and a locking means (12a) for locking the screw coupling of
the bolt shaped capacitance adjuster (12) and the threaded blind
hole (61b) at an arbitrary position.
5. The electric fence voltmeter of claim 1, wherein the body case
(60) is made of a conductive material, and the sensor case (61) is
made of a non-conductive material.
6. The electric fence voltmeter of claim 5, wherein the body case
(60) is made of an aluminum, and the sensor case (61) is made of a
transparent plastic.
7. The electric fence voltmeter of claim 5, wherein the body case
(60) is connected electrically to the ground (P2) of the
voltmeter.
8. The electric fence voltmeter of claim 1, wherein: the display
unit (40) further displays the start of the high voltage pulse; and
the start of the pulse and the value of the measured peak voltage
are displayed in the form of sound, light, characters, or a
combination thereof.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present disclosure relates to a voltmeter for measuring
the peak voltage of a high voltage pulse applied to an electric
fence. More particularly, the present disclosure relates to the
electric fence voltmeter having high measurement coupling factor
that eliminates the need for connecting the ground terminal of the
voltmeter to the earth. The high coupling factor can be achieved by
optimizing the distribution of various stray capacitances acting on
the voltmeter.
Related Art
[0002] An electric fence prevents the intrusion of wild animals, or
the escape of livestock cultivated in the fence. A pulse shaped
high voltage generated from an energizer is applied between the
earth and the fence wire which is supported by the insulators
installed around fence posts. If an animal is in contact with the
fence wire, a strong pain is caused by an electric shock due to the
circulating current flowing through the animal.
[0003] Most of the electric fence energizer has a transformer that
has more turns on the secondary winding than the primary to
generate a high voltage pulse having a peak value of 2 kV to 10 kV.
The high voltage pulse is induced from the secondary winding of the
transformer when the electric charge stored in an energy storage
capacitor is discharged through the primary winding. The reason for
raising the fence voltage up to 10 kV is to breakdown the
electrical insulating effect that the animal hairs have.
[0004] The period of applying high voltage pulses to the electric
fence wire is usually 0.75 to 1.5 seconds, and the pulse duration
is 5 to 500 microseconds. The high voltage pulses have normally
positive polarity relative to the ground, but may also have a
negative polarity.
[0005] Sometimes, the electric fence experiences unwanted low
voltage on the fence wire due to the various reasons including the
failure of the electric fence energizer itself, the fence wire in
contact with trees or weeds, the broken or sagging fence wire on
the ground, and the broken insulators.
[0006] Once the fence voltage is lowered, the current flowing
through the animal becomes weak or may not flow at all. Thus, in
order to maintain the electric fence effectively, the voltage
applied to the fence wire must be measured frequently by using an
adequate voltmeter to ensure that a predetermined high voltage is
applied.
[0007] In JP Pat. No. 03145408 U, issued to Tiger company, on Sep.
17, 2008, the patent discloses a non-contact type portable voltage
measuring device for electric fences. The device utilizes the
phenomenon that the intensity of the electromagnetic wave emitted
from the electric fence wire to the surroundings is proportional to
the strength of the voltage applied to the wire. The
electromagnetic wave signal detected by the antenna of the device
is amplified by a high gain amplifier. The device is easy to use in
a non-contact manner without need to make a ground connection to
the earth. However, this device has a problem with a poor
measurement accuracy especially when the fence voltage is low.
[0008] Detailed discussion on recent technologies is provided in
"The design of an electric fence fault finder", M. Sc. Thesis,
Massey University New Zealand by Glen McGillan (2009), pp 123-130.
The article describes a detailed design of the peak voltage
detecting circuits. The voltage measuring circuits are based on a
resistor voltage divider of which the output is fed to additional
two peak detector circuits to provide the peak voltages of both
positive and negative pulses. The peak voltages are read by A/D
(analog to digital) conversion channels of an MCU (micro controller
unit) and displayed on a display unit. The test result shows that
the voltage readings taken without an earth connection are
approximately 10% lower than the readings taken when the earth
connection is present.
[0009] Thus, referring to the prior art literature and the
commercially available products, it becomes evident that the
electric fence voltmeter based on known technologies has to be
grounded to the earth to measure a voltage adequately.
[0010] In more detail, a ground rod connected to a ground terminal
of the voltmeter via a lead wire has to be inserted into the earth
prior to contacting the probe of the voltmeter to the fence wire.
In this reason, the measurement process of the conventional
voltmeters is known to be too cumbersome, and takes long time to
use.
[0011] In addition, since the high voltage probe of the
conventional voltmeter is usually disposed close to the case, it
may inadvertently cause an electric shock to a user during a
measurement.
SUMMARY OF THE INVENTION AND ADVANTAGES
[0012] The present disclosure is directed to an electric fence
voltmeter which overcomes the problems arising from the known
electric fence voltmeters.
[0013] An electric fence voltmeter in a generic aspect of the
present disclosure may include: a body case 60 of which one side
has an opening; a sensor case 61 connected to the opening of the
body case 60 to protrude from the body case 60; a voltage divider
10 disposed over the inside and the outside of the sensor case 61
for dividing the high voltage pulse Vp applied to a probe 11 into a
low divided voltage V2; a peak detector 20 for detecting the peak
voltage of the divided voltage V2; a display unit 40 for displaying
the peak voltage; and an MCU 30 for controlling the input and the
output of the elements constituting the voltmeter 1.
[0014] The electric fence voltmeter 1 may have a sufficiently high
measurement coupling factor enough to eliminate the need for
connecting the ground of the voltmeter to the earth. The
measurement coupling factor is defined as the ratio of the voltage
detected from the voltmeter to the voltage applied to the electric
fence.
[0015] More specifically, the measurement coupling factor may be
increased by adequately arranging the various stray capacitances
acting on the voltmeter.
[0016] In order to provide a means for setting up the voltage
division ratio, the voltage divider 10 may have a capacitance
adjuster.
[0017] According to the exemplary embodiments, the present
disclosure provides a voltmeter that can measure the peak voltage
of an electric fence accurately without need to make a ground
connection to the earth, thereby having an advantage of becoming
easy to use and allowing quick measurement.
[0018] In addition, the voltmeter has a low risk of an electric
shock during the measurement.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a block diagram of the electric fence voltmeter
according to the present disclosure.
[0020] FIG. 2 is an equivalent circuit of stray capacitances acting
on the voltage divider.
[0021] FIG. 3 is a plan view of the electric fence voltmeter
according to the first embodiment of the present disclosure.
[0022] FIG. 4 is a plan view of the electric fence voltmeter
according to the second embodiment of the present disclosure.
DETAILED DESCRIPTION OF THE INVENTION
[0023] The present disclosure may be understood more readily by
reference to the following detailed description of embodiments and
the accompanying drawings. However, the present disclosure may be
embodied in many different forms, and should not be construed as
being limited to the embodiments set forth herein. Rather, these
embodiments are provided so that this disclosure will be thorough
and complete and will fully convey the concept of the invention to
those skilled in the art, and the present disclosure will only be
defined by the appended claims.
[0024] The terminology used herein is defined in consideration of
the function of corresponding elements used in the present
disclosure and may be varied according to users, operator's
intention, or practices. In addition, an arbitrarily defined
terminology may be used in a specific case and will be described in
detail in a corresponding description paragraph. Therefore, the
terminology used herein is for the purpose of describing particular
embodiments only and is not intended to be limiting of the
invention.
[0025] Referring to FIG. 1, the electric fence voltmeter 1
includes:
[0026] a body case 60 of which one side has an opening;
[0027] a sensor case 61 connected to the opening of the body case
60 to protrude from the body case 60;
[0028] a voltage divider 10 disposed over the inside and the
outside of the sensor case 61 for dividing the high voltage pulse
Vp applied to a probe 11 into a low divided voltage V2;
[0029] a peak detector 20 for detecting the peak voltage of the
divided voltage V2;
[0030] a display unit 40 for displaying the peak voltage; and
[0031] an MCU 30 for controlling the input and the output of the
elements constituting the voltmeter 1.
[0032] The voltmeter 1 further includes a power supply unit 50 for
supplying electric power to the elements constituting the
voltmeter.
[0033] Now, the working principle of a voltage divider 10 according
to the present disclosure will be described in detail.
[0034] Referring to FIGS. 1 and 2, the voltage divider 10 is a
capacitor voltage divider composed of a capacitor C1 of which the
first electrode C1a is connected to a probe 11, and a capacitor C2
of which one electrode is connected to the second electrode C1b of
the capacitor C1 and the other electrode is connected to a ground
P2.
[0035] When a high voltage is applied between the probe 11 and the
ground P2, a circulating current flows through the capacitor C1 for
charging the capacitor C2. At this time, the capacitors C1 and C2
are charged with the same amount of electric charge (Q). Thus, the
capacitors C1 and C2 have the voltage potential of V1=Q/C1, and
V2=Q/C2. In the formula, C1 and C2 represent the capacitances of
the capacitor C1 and C2, respectively.
[0036] The voltage division ratio (Rd) is expressed as the divided
voltage V2 divided by the input voltage Vp. In other words, the
voltage division ratio (Rd) is V2/Vp, or V2/(V1+V2). The voltage
division ratio (Rd) can be expressed with the capacitance of the
capacitors C1 and C2, as shown in equation (1).
Rd = C 1 C 1 + C 2 ( 1 ) ##EQU00001##
[0037] According to equation (1), it can be seen that the
capacitance of the capacitor C1 needs to be small and that of the
capacitor C2 needs to be large to make the voltage division ratio
(Rd) small to be suited for measuring a high voltage applied to an
electric fence.
[0038] The present disclosure is to simplify the complicated
measurement process that the prior art has. In other words, the
present disclosure is to provide an electric fence voltmeter having
high measurement coupling factor so that the voltmeter is able to
measure accurately even if the readings are taken without a ground
connection to the earth. The high coupling factor may be achieved
by optimizing the distribution of various stray capacitances acting
on the voltmeter through the shape and arrangement of the voltage
divider 10.
[0039] Now, referring to the FIG. 2, the various stray capacitances
acting on the electric fence voltmeter 1 will be described.
[0040] FIG. 2 shows the voltage dividing capacitors C1 and C2, a
first stray capacitance C5 existing between the probe P3 and the
ground P2 of the voltmeter, and a second stray capacitance C8
existing between the ground P2 of the voltmeter and the earth P0
via a user P1 who is holding the voltmeter.
[0041] The voltmeter measures the voltage Vp applied to both ends
of the voltage divider 10 instead of the voltage Vf applied between
the electric fence wire and the earth. Referring to FIG. 2, the
relationship between the voltages Vf and Vp is shown in equation
(2).
V p = C 8 C 1 C 2 C 1 + C 2 + C 5 + C 8 Vf = K Vf ( 2 )
##EQU00002##
[0042] In equation (2), the proportional constant K is the
measurement coupling factor of the electric fence voltmeter 1.
Therefore, it can be seen that the measurement coupling factor is
maximized by converging to 1 as the second stray capacitance C8
becomes larger. However, the measurement coupling factor is
minimized by converging to zero as the capacitance C1C2/(C1+C2) or
the first stray capacitance C5 becomes larger.
[0043] That is, the second stray capacitance C8 needs to be large,
and the capacitance C1C2/(C1+C2) and the first stray capacitance C5
need to be small to increase the measurement coupling factor of the
voltmeter 1. The term C1C2/(C1+C2) is the capacitance of the
voltage divider 10 where the capacitances C1 and C2 are connected
in series.
[0044] The second stray capacitance C8 is determined by a third
stray capacitance C6 existing between the user P1 and the ground P2
of the voltmeter 1, and a fourth stray capacitance C7 that exists
between the user P1 and the earth P0. The capacity of the fourth
stray capacitance C7 is known to be approximately 100 pF.
[0045] Therefore, the third stray capacitance C6 should be kept
large to increase the second stray capacitance C8. To this end, the
body case 60 where a user contacts with may be made of a conductive
material and connected to the ground P2 of the voltmeter 1.
[0046] On the other hand, for example, in the case that the voltage
divider 10 is to divide 10 kV into 1V, referring to equation (2),
the capacitance of the capacitor C1 can be chosen to be as small as
0.1 pF to increase the measurement coupling factor of the voltmeter
1. In this case, the capacitance of the capacitor C2 is determined
to be 1 nF from equation (1).
[0047] Since the capacitance of the capacitor C1 is so small, the
electrodes of the capacitor C1 should be spaced at a significant
distance apart from each other if the electrodes are placed in the
air.
[0048] It is also necessary to decrease the stray capacitance C5 to
improve the measurement coupling factor. It is accomplished by
placing the first electrode C1a of the capacitor C1 apart from the
body of the voltmeter 1 at a significant distance, too.
[0049] In addition, the probe 11 which is connected to the first
electrode C1a of the capacitor C1 needs to be spaced apart from the
body case 60 at a significant distance to prevent an electric shock
to a user during a measurement.
[0050] Now, the first embodiment of the present disclosure which
reflects the aforementioned design considerations will be described
in detail.
[0051] Referring to FIG. 3, in the first embodiment, the electric
fence voltmeter 1A includes:
[0052] a cylindrical body case 60 of which one side has an
opening;
[0053] a cylindrical sensor case 61 connected to the opening of the
body case 60 to protrude from the body case 60;
[0054] a printed circuit board 70 in which a part of the voltage
divider 10, the peak detector 20, the MCU 30, the display unit 40,
and other electronic parts are assembled; and
[0055] a power supply unit 50 for supplying electric power to the
elements constituting the voltmeter.
[0056] The capacitor C1 of the voltage divider 10 has the first
electrode C1a placed on the outer end of the sensor case 61 in the
form of a surface electrode, and the second electrode C1b placed in
the inside of the sensor case 61 in the form of a surface electrode
that is spaced oppositely to the first electrode C1a at a
predetermined gap.
[0057] The body case is composed of a first body case 60a and a
second body case 60b being coupled by a screw thread type coupling
means 63. The body cases 60a and 60b are made of a conductive
material, and the sensor case 61 is made of a non-conductive
material.
[0058] Locking protrusions 60c and 61a are formed on the inside of
the first body case 60a and the outside of the sensor case 61. The
sensor case 61 inserted into the body case 60a is engaged by the
protrusions 60c and 61a, and fixed each other by a screw thread
type hollow fastening means 62 made of a conductive material.
[0059] At this time, a disc-shaped fixing member 70a of the printed
circuit board 70 formed around the board 70 is arranged between the
protrusion 61a and the fastening means 62. Thus, a negative power
terminal 71a placed on the surface of the fixing member 70a is
connected electrically to the body case 60a via the conductive
fastening means 62.
[0060] Aluminum can be applied as the conductive material, and a
transparent plastic such as polycarbonate resin or acrylic resin
can be applied as the non-conductive material for the sensor case
61.
[0061] Once the voltmeter 1 is assembled, the negative pole of the
battery 51 is connected electrically to the ground P2 of the
printed circuit board 70 via a spring 53, a switch 52, the body
cases 60a and 60b, the fastening means 62, and the negative power
terminal 71a. The positive pole of the battery 51 is connected to
the printed circuit board 70 via a positive power terminal 71b.
[0062] Accordingly, the electric potential of the conductive cases
60a and 60b becomes same with the potential of the negative pole of
the battery 51 which is the ground P2 of the voltmeter 1.
[0063] When the switch 52 is turned on, the MCU 30 monitors the
divided voltage V2 to detect the start of a pulse, and measures the
peak voltage detected from the peak detector 20 at the peak of the
pulse. The start of the pulse signal and the measured peak voltage
are transmitted to the display unit 40.
[0064] The display unit 40 receives the start of the high voltage
pulse and the measured peak voltage from the MCU 30, and may
indicate them in the form of sound, light, characters, or a
combination thereof.
[0065] For example, a buzzer 42 or an LED 43 can be used to make
sound or emit light for indicating the occurrence of a high voltage
pulse. In addition, it is possible to light a plurality of lamps
(not shown) selectively depending on the strength of the measured
voltage. Also, the measured voltage can be displayed in the form of
characters through a character display unit 41.
[0066] Thus, the body case 60 and the sensor case 61 may have
openings (not shown) for passage of sound and transparent parts
(not shown) for passage of light so that the display unit 40 is
recognized from the outside.
[0067] Meanwhile, referring to FIG. 4, in the second embodiment of
the present discloser, the voltmeter 1B has a means for adjusting
the capacitance of the capacitor C1 to set up the voltage division
ratio (Rd). The capacitance of the capacitor C1 can be adjusted by
modulating the equivalent distance between the first electrode C1a
and the second electrode C1b of the capacitor C1.
[0068] That is, in the second embodiment, the electric fence
voltmeter 1B further includes:
[0069] a bolt shaped capacitance adjuster 12 made of a conductive
material screwed through a hole formed at the center of the first
electrode C1a of the capacitor C1 into a threaded blind hole 61b
formed inside of the sensor case 61 directed to the second
electrode C1b; and
[0070] a locking means 12a for locking the screw coupling of the
capacitance adjuster 12 and the threaded blind hole 61b at an
arbitrary position,
[0071] on the electric fence voltmeter 1A.
[0072] The head of the bolt shaped capacitance adjuster 12 may also
be used as the probe 11 of the voltmeter.
[0073] The locking means 12a may be a nut type. The nut also has a
function of fixing the first electrode C1a of the capacitor C1 on
the sensor case 61. To this end, a spring washer 12b may be
disposed between the nut and the electrode C1a.
[0074] In order to demonstrate the performance of the present
disclosure, a prototype according to the second embodiment shown in
FIG. 4 is fabricated. The major specification of the prototype is
as follows: the voltage division ratio (Rd) is 1/10,000, the
capacitance of C2 is 1 nF, and the protruded length of the sensor
case 61 is 75 mm. The capacitance of C1 is obtained to be 0.1 pF by
using the capacitance adjuster 12.
[0075] As a test result, the prototype voltmeter shows that the
voltage readings taken without a ground connection to the earth are
approximately 0.5% smaller than the readings taken with the ground
connection. This degree of error may not cause problem in the
electric fence voltmeter, besides the value is much smaller than
the 10% error that the voltmeters of the prior art have.
[0076] The theoretical measurement coupling factor (K) of the
prototype voltmeter can be obtained by equation (2) as follows:
[0077] Firstly, the capacitance of the human skin is known to be in
the range of between 0.01 uF and 0.05 uF per square centimeter.
Thus, assuming that the area for gripping the conductive body case
60 of the voltmeter 1 by hand is 50 square centimeters, the
capacitance found at the contacting area amounts to at least 0.5
uF, that is, the third stray capacitance C6 is chosen to be 0.5
uF.
[0078] Secondly, the other design data necessary for computing the
measurement coupling factor (K) are defined as follows: as
mentioned previously, the fourth stray capacitance C7 is 100 pF,
the capacitance of the capacitor C1 is 0.1 pF, and the capacitance
of the capacitor C2 is 1 nF, and the first stray capacitance C5 is
set equal to the capacitance of the capacitor C1. Note that the
second stray capacitance C8 is obtained by a formula
C8=C6C7/(C6+C7).
[0079] By substituting the design data defined above into equation
(2), the measurement coupling factor is obtained as K=0.998. That
is, an error of only 0.2% can be found theoretically from the
readings of the voltmeter even if the ground connection to the
earth is not present.
[0080] The errors found from the performance test and the
theoretical calculation show a slight difference. This is
considered to be due to the first stray capacitance C5 having
sensitive effect to the measurement coupling factor (K) is
estimated a little bit smaller.
[0081] According to the specifications described so far, the
present disclosure provides an electric fence voltmeter that
measures the peak voltage accurately without need to make a ground
connection to the earth, and has a low risk of an electric shock
during a measurement is provided.
[0082] While this invention has been described in connection with
what is presently considered to be practical exemplary embodiments,
it is to be understood that the invention is not limited to the
discovered embodiments, but, on the contrary, is intended to cover
various modifications and equivalent arrangements.
LIST OF REFERENCE NUMERALS
[0083] 1 hand-held voltmeter [0084] 10 voltage divider [0085] 11
probe [0086] 12 capacitance adjuster [0087] 12a locking means
[0088] 20 peak detector [0089] 30 MCU [0090] 40 display unit [0091]
50 power supply unit [0092] 51 battery [0093] 52 switch [0094] 53
spring [0095] 60 body case [0096] 61 sensor case [0097] 61b
threaded blind hole [0098] 62 fastening means [0099] 63 coupling
means [0100] 70 printed circuit board [0101] 71a negative power
terminal [0102] 71b positive power terminal
* * * * *