THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
NATURE OF THE INVENTION

PROTECTION OF METER FROM TAMPER DEVICE
A) Technical Field
1. The present invention speaks generally about method of protection of electricity
meter from tamper device excited by spark plug which generates high frequency
signals. The present invention speaks particularly about method of protection of
electricity meter where the electricity meter is a Tri Vector meter.
2. The present invention speaks more particularly about a method of protection of
electricity meter from tamper device excited by spark plug, where the protection
is achieved by attenuating the signal at the primary end of the energy meter
which reduces the signal strength and hence protect the energy meter. The
present invention speaks more particularly about a method of protection of
electricity meter from tamper device excited by spark plug, where the protection
is provided by keeping the distance between phase and base plate lesser then the
distance between phase and the electronic circuit of the electric meter.
B) Background of the invention
3. Electricity is one of the basic necessities in the present day. The electricity in
INDIA is provided by the government. The government has installed electricity
meter for billing the electricity consumer according to the power consumption of
user. In earlier times there were mechanical electricity meters which could be
tampered easily by putting a magnet in the vicinity of meter which slows down or
stops the meter. With the growth of technology there was the advent of digital
meter which were not affected by the magnet. The digital meters were tamper
free for sometime. However, at a later stage new methods were devised to

tamper the digital meters. A few of the available tamper monitoring and tamper protection methods are being described in the following patents.
4. In US patent numbered 4,542,337, an electro mechanical anti-tampering device
for electric meters has been described. In it there is an apparatus for indicating
electric meter tamper is disclosed having a switch provided with normally closed
contacts in the nature of an enclosed race having a central inner contact and a
plurality of spaced outer contacts operating in conjunction with a conductive,
magnetic ball disposed in the race such that when the ball is in a stable position
one of the outer contacts is electrically connected to the center contact and when
the ball is disturbed from a stable position the circuit is temporarily opened. The
system further includes an actuator device responsive to the opening of the
normally closed contacts and an indicator device responsive to the actuator
device to indicate the opening of contacts which marks the meter or otherwise
signals a tampering incident. Thus, the system is sensitive to changes in position
of the meter, vibration and/or magnetic fields, which are sufficient to cause said
contacts to temporarily open.
5. In US patent numbered 5,086,292 a tamper detection device for utility meter has
been described. The system detects tampering with a utility meter which provides
not only an indication that tampering has occurred but also sufficient
information to enable an estimation of actual consumption to be made as
opposed to the tampered metered consumption. The device includes a plurality7
of tampering sensors sensing tilt, electric field, magnetic field, temperature,
sound, reverse rotation of a moving element and excessive difference between
metered consumption and an approximate actual consumption. The device also
measures the movement of the moving element. These sensed signals are
recorded in sequential time periods of for example eight hours so that an analysis
can be made on a daily basis to provide an accurate pattern of consumption as
opposed to the tampered meter consumption pattern.

6. In US patent numbered 6,801,865 a method of meter monitoring and tamper
protection has been described. The commodity-meter management system
includes commodity meters (e.g., electrical energy meters, gas meters, and/or
water meters), one or more servers, and a communications application to
communicate between the meters and the servers. The meters are connected to
the servers via communication mediums. The communications application can
communicate bi-directionally in real-time between the meters and the servers via
the communication mediums. The communications application can determine
the actual configuration parameters according to which the meter is operating at
any given time. In order to detect theft of a commodity, the communications
application can compare the actual configuration parameters to default
configuration parameters. If the actual and default configuration parameters arc
not equal, substantially equal, or within a predetermined threshold, the
communications application indicates that a tamper event has occurred.
7. In US patent numbered 6,236,197 an apparatus and method for detection in a
multiphase system has been described. It consist of an apparatus for
determining loss of reference voltage (indicating possible tampering) in a 2-
element electronic meter that includes a processor for determining electrical
power from voltage and current signals, and a display for indicating an operating
status of the meter. To determine if the reference voltage of the meter in a 3-wirc
delta or network installation has been lost, a measurement of the phase angle
difference between the two phases is made. If the phase difference is equal to a
predetermined value, the meter indicates on the display that loss of reference
voltage and possible tampering has taken place. The apparatus may further be
adapted to determine a length of time that this condition has occurred such that
the appropriate enforcement and billing agencies may be informed.

8. The above mentioned patents speak about various available methods for tamper
determination and tamper protection. The present day digital meters are
tampered by passing a high amplitude high frequency signal using a spark plug.
The present available methods for tamper protection does not address to this
problem. The present invention provides a novel method of tamper protection
by providing a grounding mechanism which reduces the amplitude of this high
amplitude signal and thus protects the important components of the meter from
being destroyed. The present invention protects from tamper caused by high
frequency and high amplitude signal.
C) Objects of the present invention
9. A primary objective of the present invention is to provide a method to immune
tri vector meter from high amplitude high frequency tamper induced by spark
plug.
10. Another objective of the present invention is to provide a method to immune tri
vector meter from high amplitude high frequency tamper by attenuating the
signal at primary side so that the tamper signal strength reduces.
11. Another objective of the present invention is to provide a method to immune tri
vector meter from high amplitude high frequency tamper by providing
differential chokes for filtering the signal.
12. Another objective of the present invention is to provide a method to immune tri
vector meter from high amplitude high frequency tamper by keeping the distance
between phase and base plate lesser then the distance between phase and the
electronic circuit of the tri-vector meter.

13. Another objective of the present invention is to provide a method to immune tri
vector meter from high amplitude high frequency tamper and provides accurate
measurement and billing.
D) Statement of the invention
14. Accordingly the present provides a method to immune an electric meter from
tamper device excited by spark plug which generates high frequency signals.
15. The circuit for tamper protection consist of connecting differential chokes a
neutral between the three phase and the neutral. The tamper as well as normal
signal first comes to the base plate even if the signal is applied on the phase.
16. The method involved for isolating the tamper is by maintaining the distance
between phase and base plate is less then the distance between phase and the
electronic circuit. The furthermost end of the base plate is connected to the PCB
of the meter.
17. Due to the large size of the base plate the high amplitude of the signal is
considerably reduced. The signal is then passed through some more filter which
will remove the tamper and the signal reaching the electronic part of the meter
will be tamper free.
E) Brief description of the diagram
18. The diagram in FIG.l shows a setup for protection of meter from tamper device
excited by spark plug which generates high frequency signals.

F) Detailed description of the invention
19. The electric meter is basically designed to bill the customer according to the
power consumption. Each unit consumes a large amount of power and so any
unauthorized consumption of power will lead to large loss to the government.
Each meter has an IR port or optical port. There is a meter reading instrument.
The meter reading instrument is connected to the optical port and it sends
commands to get back data about the power consumption.
20. The present day digital meter is tampered by a small tamper device. The tamper
device consists of a spark plug connected to a transformer. The spark plug is
excited by a 50 Hz signal which generates 35 kilo Watt pulse signal with an
amplitude of around 25 KV to 40KV having a frequency of 15 to 30 kHz. This
results in a ringing waveform which is applied direcdy to the terminals of the
meter. The average energy of this signal is not much high, but it results in a very
high instantaneous energy. The internal memory registers store erratic values and
the data gets corrupted. As a result of the data corruption the consumer has to
pay the Electricity board only the basic minimum amount which is very small.
This is a great loss to the Electricity Board or Utility.
21. The present invention provides an effective method of removing tamper induced
by a high amplitude high frequency signal. The diagram in fig.l (101) shows a
complete setup for isolating the meter from the above mentioned tamper. The
internal base plate is connected to grounding plate (103). The ground plate (103)
is connected to neutral line.
22. Any external signal first comes to the base plate (103) even if the signal is applied
directly to the phase terminals. The signal first passes through differential chokes
(102) between three phase and neutral as shown by fig.l (101).

23. The distance (104) between phase and base plate (103) is lesser then the distance
between phase and the electronic circuit. The electronic circuit is the PCB board
shown by dotted line (106). The furthermost end of the base plate (103) is
connected back to the PCB board.
24. The tamper signal first comes to the base plate which reduces the strength
(amplitude) considerably and brings it within safe limits. The circuit is then
provided by filters and conditioning circuit (105) which further fine tunes the
circuit before it is fed to the circuit.
G) Scope of the invention
25. The present invention has many advantages over the existing inventions for
removing tamper from an electric meter.
26. A primary advantage of the present invention is to have a method to immune tri
vector meter from high amplitude high frequency tamper induced by spark plug.
27. Another advantage of the present invention is to have a method to immune tri
vector meter from high amplitude high frequency tamper by keeping the distance
between phase and base plate lesser then the distance between phase and the
electronic circuit of the tri-vector meter.
28. Another advantage of the present invention is to have a method to immune tri
vector meter from high amplitude high frequency tamper, where the immunity to
the meter can be provided in an old meter with easy compatibility.
29. Another advantage of the present invention is to have a method to immune tri
vector meter from high amplitude high frequency tamper, where the method to
provide immunity is cost effective.

30. Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention.

We claim:
1. A system to provide tamper protection for an electric meter which comprises of:
a) a base plate for grounding purpose,
b) a differential choke for filtering signal,
c) a signal conditioning circuit for conditioning the signal before feeding it to the
meter.

2. A system to provide tamper protection for an electric meter as claimed in claim 1,
where the base plate is connected to a differential choke.
3. A system to provide tamper protection for an electric meter as claimed in claim 1,
where the base plate end is connected to a conditioning circuit.
4. A system to provide tamper protection for an electric meter as claimed in claim 1,
where the differential choke is connected to the phase and filters the incoming
signal.
5. A system to provide tamper protection for an electric meter as claimed in claim 1,
where the signal conditioning circuit conditions the signal before sending it to the
electric meter.
6. A method to provide tamper protection for an electricity meter, where the method
comprises of:

a) Connecting a differential choke filter between the three phases and the
neutral,
b) Connecting the neutral to one end of the base plate,
c) Connecting the other end of the base plate to the printed circuit board.
7. A method to provide tamper protection for an electricity meter as claimed in claim 6,
where differential choke is connected between the three phases and the neutral to
reduce noise induced by the tamper device.
8. A method to provide tamper protection for an electricity meter as claimed in claim 6,
where the neutral is connected to one end of the base plate to reduce the amplitude
of the tamper signal and thus protect the electronic circuit from the tamper signal
9. A method to provide tamper protection for an electricity meter as claimed in claim 6,
where the other end of the base plate is connected to the PCB to reduce the
amplitude of the tamper signal and thus protect the electronic circuit from the
tamper signal.
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