THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE NATURE OF THE INVENTION

MAGNETIC TAMPER DETECTION DEVICE FOR ENERGY
METER
A) TECHNICAL FIELD
[0001] The present invention generally relates to energy meter such as watt- hour meter used for measuring the domestic and industrial electrical power consumption and particularly to sensor devices used for detecting a tampering event in the energy meter. The present invention more particularly relates to a solid state device used for detecting the tampering of the energy meter using magnetic flux.
B) BACKGROUND OF THE INVENTION
[0002] An electric meter or energy meter is a device that measures the amount of electrical energy suppUed to a residence or business. The most common type is more properly known as a (kilo)watt-hour meter or a joule meter. The most common unit of measurement on the electricity meter is the kilowatt-hour which is equal to the amount of energy used by a load of one kilowatt over a period of one hour, or 3,600,000 joules. The demand is normally measured in watts, but averaged over a period, most often a quarter or half an hour.

[0003] The meters for measuring single phase energy are also available. It also provides capabilities like Maximum demand with date & time, a kWh Backups, etc. The modern electricity meters operate continuously by measuring the instantaneous voltage (volts) and current (amperes) levels and computing the product of these to give an instantaneous electrical power (watts) which is then integrated against time to give the energy consumed (in joules, kilowatt-hours etc). The meters fall into two basic categories, namely, the electromechanical meters and the electronic meters.
[0004] The most common type of electricity meter is the electromechanical induction meter. The electromechanical induction meter operates by counting the revolutions of an aluminum disc which is made to rotate at a speed proportional to the power. The number of revolutions is thus proportional to the energy used. It consumes a small amount of power, typically around 2 watts.
[0005] The metallic disc is acted upon by two coils. One coil is connected in such a way that it produces a magnetic flux in proportion to the voltage and the other produces a magnetic flux in proportion to the current. This produces eddy currents in the disc and the effect is such that a force is exerted on the disc in proportion to the product of the instantaneous current and voltage. A permanent magnet exerts an opposing force proportional to the speed of rotation of the disc so that the rotation of the disc is stopped, when power is not supplied. As a result, the disc is rotated at a speed proportional to the power being used. The type of meter described above is used on a single-phase AC supply. Different phase configurations use additional voltage and current coils.

[0006] Some of the electricity meters are solid state type and they display the energy consumed on an LCD module, while the electronic meters can be read automatically. In addition to measuring the consumption of the electricity, the solid state meters may also record other parameters of the load and supply such as maximum demand, power factor and reactive power used etc. They may also include the electronic real time clock mechanisms to compute a value, rather than an amount, of electricity consumed, with the pricing varying of by the time of day, day of week, and seasonally.
[0007] The AMR (Automatic Meter Reading) and RMR (Remote Meter Reading) describe various systems that allow meters to be checked by without the need to send a meter reading personnel out. This may be effectively achieved using the off-site metering technology. The electronic meter is placed at the junction point where all the connections originate, inaccessible to the end-user, and it relays the readings via the AMR technology to the utility.
[0008] The meters may be manipulated so as to make them under-register or even run backwards, effectively allowing usage of power without paying for it. There are several forms of tampering that are effectively done on inductive meters and solid state Energy Meters. The magnets above 0.5 tesla can saturate the magnetic circuits, causing the loss of registration. Some industry traditionally inserts rectifiers in light-bulb sockets to induce DC loads. The grounded, disconnected or reversed terminals also cause misregistration. Some industries historically alternated the inductive motors and capacitive loads (such as arc-smelters) to alternately run the meters forward then backward.

[0009] Hence there is a need to develop a system to detect the tampering of the energy meters due to high magnetic flux reliably and cheaply. Also there is a need to provide a permanent record of the tampering event due to magnetic flux for future reference and evidence.
C) OBJECT OF THE INVENTION
[0010] The primary object of the present invention is to develop a system to detect the tampering of the energy meter by high magnetic flux reliably and cheaply.
[0011] Another object of the present invention is to develop a system provided with solid state detector to detect the tampering of the energy meter by high magnetic flux.
[0012] Yet another object of the invention is to develop a system to detect the magnetic flux with high sensitivity.
[0013] Yet another object of the present invention is to develop a system to detect the magnetic flux reliably and independently of the magnetic flux rate.
[0014] Yet another object of the present invention is to develop a system to detect the applied magnetic filed/flux in any direction reliably and easily.
[0015] Yet another object of the invention is to develop a magnetic flux tamper detection system to withstand high magnetic flux.

[0016] Yet another object of the present invention is to develop a magnetic flux tamper detection system to detect steady and alternate current magnetic flux reliably and accurately.
[0017] Yet another object of the present invention is to develop a magnetic flux tamper detection system to provide a permanent record of the tampering event.
[0018] Yet another object of the present invention is to develop a magnetic flux tamper detection system to record the energy by assuming maximum load current, irrespective of the actual load current used during the tamper event.
[0019] Yet another object of the present invention is to develop a magnetic flux tamper detection system to provide a permanent record that may be displayed on LCD display to indicate the tampering of the meter by external magnetic field and the normal working condition of the meter.
[0020] These and other objects and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.
D) SUMMARY OF THE INVENTION
[0021] The abovementioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.

[0022] The various embodiments of the present invention provide a system and a method to detect the tampering of the solid state energy meter by magnetic flux reliably and efficiently.
[0023] According to one embodiment of the invention the sensor includes plurality of resistors that are arranged in a Wheatstone bridge network to detect the applied magnetic field. The resistors are mixed with ferrous materials so that the resistance values of the resistors are changed based on the applied magnetic field. The Sensor is sensitive to the direction of field applied. The resistors in the opposite arms of the Wheatstone bridge are arranged at 90° to each other so that the magnetic flux in any direction may be detected reliably and accurately. The sensor detects an applied magnetic filed and outputs a signal. The output signal from the sensor is amplified and conditioned. The amplified and smoothened detection signal is converted into a digital signal which is input to a micro controller for time stamping of the detected event and recording in a permanent memory for future retrieval of tamper detection data.
[0024] The micro controller is installed with an intelligent software to calculate and record the consumed electrical energy by assuming the maximum load current during the magnetic tamper event instead of actual consumption thereby penalising the consumer for malpractice. Thus the consumer is deterred from applying an external magnetic field to the meter and is punished to pay for maximum load instead of actual consumption. The micro controller calculates the actual consumption, when the external magnetic field is removed. The micro controller activates a display device like Liquid Crystal Display (LCD) device to indicate the detected tampering of the energy meter due to magnetic field and the normal working condition of the energy meter.

[0025] According to another embodiment of the present invention, a magnetic tamper detection method in energy meter involves arranging sensors in a Wheatstone bridge network. The sensors are the resistors mixed with ferrous material so that the resistance values of the resistors are changed with respect to the applied magnetic field. The resistors provided in the opposite arms of the Wheatstone bridge network are arranged at 90 degrees to each other to detect the magnetic field applied in any direction reliably and accurately. The output of the sensor is amplified and output to a comparator. The amplified signal is compared with the preset threshold values produced by the threshold value generator to detect a magnetic tamper event. The output signal from the comparator is level shifted and fed to a micro controller. The micro controller detects a magnetic tamper event based on the received signal from the comparator and calculates the duration of the tamper detection event. The micro controller records the magnetic tamper detection event with a time stamp in a memory such as electrically erasable programmable read only memory (EEPROM) for future evidence. The memory can hold data for 100 years. The micro controller forwards the data to user to take suitable action with respect to the meter tamper event. The micro controller activates a display device like Liquid Crystal Display (LCD) device to indicate the detected tampering of the energy meter due to magnetic field and the normal working condition of the energy meter.
[0026] Thus the sensor of the present invention produces an output voltage which is independent of rate of the magnetic flux detected. Normally in inductive sensors, the output voltage is varied proportionately with respect to the detected magnetic flux. The smaller the variation in flux, the smaller is the output voltage. The detection system uses the semiconductor technology rather than metals. The mobility of ions in

semiconductors can be controlled easily by adding the impurities. They are easily re¬producible and the reliability is high. The cost of the system is reduced.
[0027] Thus the present invention provides a detection system to prevent the tinkering of the energy meter with applied magnetic field reliably and cheaply. The system detects the magnetic field applied in any direction to improve the efficiency of magnetic tamper detection process. The system detects the tampering of the energy meter by an applied magnetic field with high sensitivity. The system detects the magnetic tampering event reliably and accurately regardless of the intensity of the applied magnetic field. The rate of detection is independent of the magnetic flux. The system is able to measure both the steady and the alternate current magnetic flux applied on the energy meter. The system provides a permanent evidence for future investigation by storing the detection data in a memory for 100 years. The system counts and records the number of magnetic tamper detection events. The system stores the detected magnetic tamper detection event with a time stamp and the duration of each magnetic tamper detection event in the memory such as EEPROM. The system helps to stop the energy theft. During magnetic tampering event, the microcontroller calculates and records the consumed electrical energy by assxaming the maximum load current irrespective of actual load current to punish the guilty customer. Thus the consumer is deterred from indulging in malpractice or applying an external magnetic field to the meter.
[0028] These and other objects and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.

E) BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:
[0030] FIGURE.l illustrates the circuit diagram of a sensor in the magnetic tamper detection system according to one embodiment of the present invention.
[0031] FIGURE.2 illustrates the block diagram of the magnetic tamper detection system according to one embodiment of the present invention.
[0032] FIGURE. 3 illustrates a flow chart explaining the magnetic tamper detection method in an energy meter according to one embodiment of the present invention.
[0033] Although specific features of the present invention are shown in some drawings and not in others. This is done for convenience only as each feature may be combined with any or all of the other features in accordance with the present invention.
F) DETAILED DESCRIPTION OF THE INVENTION
[0034] In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which the specific embodiments that may be practiced is shown by way of illustration. These embodiments are described in sufficient

detail to enable those skilled in the art to practice the embodiments and it is to be understood that the logical, mechanical and other changes may be made without departing from the scope of the embodiments. The following detailed descriptidn is therefore not to be taken in a limiting sense.
[0035] The various embodiments of the present invention provide a system and method for detecting the tampering of an energy meter with an applied magnetic field easily, reliably, accurately and cheaply.
[0036] According to one embodiment of the present invention, the magnetic tamper detection system has a sensor to detect and measure a magnetic field applied on an energy meter. The sensor has plurality of resistors that are arranged in a Wheatstone bridge network to detect the applied magnetic field. The resistors are mixed with ferrous materials so that the resistance values of the resistors are changed based on the applied magnetic field. The Sensor is sensitive to the direction of field applied. The resistors in the opposites arms of the Wheatstone bridge are arranged at 90° to each other so that the magnetic flux in any direction may be detected reliably and accurately. The sensor detects an applied magnetic filed and outputs a corresponding signal.
[0037] The output signal from the sensor is DC clamped and amplified. The amplified sensor output signal is fed to a comparator. An upper threshold level generator and a lower threshold level generator are connected to the comparator to produce upper threshold level and a lower threshold level respectively. The received and amplified

sensor output signal is compared with the generated lower and upper threshold values to judge whether the amplified signal exceeds the generated threshold value levels to detect a magnetic tamper detection event. The output signal from the comparator is passed through a logic circuit device such as OR logic gate device. The level of the comparator output signal is level converted and input to a microcontroller so that the level converted signal is within the acceptable range of the micro controller. The amplified and smoothened detection signal is converted into a digital signal which is input to a micro controller for time stamping of the detected event and recording in a permanent memory for fijture retrieval of tamper detection data.
[0038] The microcontroller records the detected magnetic tamper detection event in a memory such as electrically erasable programmable memory (EEPROM) with a time stamp for fiature evidence. The micro controller calculates and records the duration of each magnetic tamper detection event. The micro controller also counts and the records the number and frequency of magnetic tamper events in the memory. The memory may store the data for 100 years.
[0039] The micro controller is installed with an intelligent software to calculate and record the consumed electrical energy by assuming the maximum load current instead of actual consumption during a magnetic tamper event thereby penalising the consumer for malpractice. Thus the consumer is deterred from applying an external magnetic field to the meter and is punished to pay for maximum load instead of actual consumption. The micro controller calculates the actual consumption, when the external magnetic field is removed. The micro controller activates a display device such as Liquid Crystal Display

(LCD) device to indicate the detected tampering of the energy meter due to magnetic field and the normal working condition of the energy meter.
[0040] According to another embodiment of the present invention, a magnetic tamper detection method in energy meter involves arranging sensors in a Wheatstone bridge network. The sensors are the resistors mixed with ferrous material so that the resistance values of the resistors are changed with respect to the applied magnetic field. The resistors provided in the opposite arms of the Wheatstone bridge network are arranged at 90 degrees to each other to detect the magnetic field applied in any direction reliably and accurately. The output of the sensor is ampEfied and output to a comparator. The amplified signal is compared with the preset threshold values produced by the threshold value generator to detect a magnetic tamper event. The output signal from the comparator is level shifted and fed to a micro controller.
[0041] The micro controller detects a magnetic tamper event based on the received signal from the comparator and calculates the duration of the tamper detection event. The micro controller records the magnetic tamper detection event with a time stamp in a memory such as electrically erasable programmable read only memory (EEPROM) for fiature evidence. The memory can hold data for 100 years. The micro controller forwards the data to user to take suitable action with respect to the meter tamper event. The micro controller activates a display device like Liquid Crystal Display (LCD) device to indicate the detected tampering of the energy meter due to magnetic field and the normal working condition of the energy meter.

[0042] Thus the sensor of the present invention produces an output voltage which is independent of rate of the magnetic flux detected. Normally in inductive sensors, the output voltage is varied proportionately with respect to the detected magnetic flux. The smaller the variation in flux, the smaller is the output voltage. The detection system uses the semiconductor technology rather than metals. The mobility of ions in semiconductors can be controlled easily by adding the impurities. They are easily re¬producible and the reliability is high. The cost of the system is reduced.
[0043] The FIG.l shows the block circuit diagram of a sensor circuit in the magnetic tamper detection system for energy meter according to one embodiment of the present invention. The sensor includes resistors Rl, R2, R3 and R4 that are connected in the form of a Wheatstone bridge network Rl, R2, R3, R4 are in single package to detect and measure the applied magnetic field. The resistors Rl, R2, R3 and R4 are arranged respectively in four different arms of the Wheatstone bridge network so that the resistors in the opposite arms are arranged at 90 degrees to each other to detect the magnetic field applied in any direction. The resistors R1-R4 are mixed with ferrous material so that the resistance values of the resistors Rl- R4 are varied with respect to the intensity of the applied magnetic field. The junction of the resistors R4 and Rl is connected to a supply voltage Vcc, while the junction of the resistors R2 and R3 is connected to ground. The voltage Vol measured across the junction of the resistors R3 and R4 is compared with the voltage Vo2 measured across the junction of the resistors Rland R2. The value of the measured voltages Vol and Vo2 are equal in the normal circumstances, i.e. when the energy meter is not tampered with a magnetic field. The voltages Vol and Vo2 are not equal, when the energy meter is tampered with an applied

magnetic field. The difference (Vol-Vo2) in the measured voltages corresponds to the intensity of the applied magnetic field. The difference in voltage levels measured during the presence of an applied magnetic field is amplified, smoothened, conditioned and digitised. The digitised voltage difference is fed to a micro controller through a comparator to detect a magnetic tamper detection event.
[0044] The FIG. 2 shows a fianctional block diagram of a magnetic tamper detection device for energy meter according to one embodiment of the present invention. The system has a sensor to detect the applied magnetic field in any direction. The sensor has resistors arranged and connected in a Wheatstone bridge network. The resistors are mixed with ferrous material so that the resistance values of the resistors are changed with respect to the magnetic field applied on the energy meter. The resistors provided in the opposites arms of the Wheatstone bridge are arranged at 90 degrees to each other so that the sensor detect the magnetic field applied in any direction reliably with high sensitivity. The difference in the voltages measured across the two different junction arms corresponds to the intensity of the applied magnetic field. The differential voltage obtained from the bridge will be in milli volts.
[0045] A DC voltage clamp circuit is used to shift the output signal from the sensor. The DC voltage clamp circuit super imposes a DC voltage with the sensor output signal. The output of the DC voltage clamp circuit is amplified by voltage amplifier. The amplifier increases the signal with small amplitudes so that even the small variation in resistance due to applied magnetic field with small flux may be detected reliably. The gain of the

amplifier is selected based on the resolution and sensitivity to be attained. The amplified sensor signal is output to an upper window comparator and a lower window comparator.
[0046] A high threshold value generator is connected to the upper window comparator to supply a high threshold value to the upper window comparator. The upper window comparator judges whether the pulse height width of the received sensor output signal from the voltage amplifier is more than the supplied upper threshold value.
[0047] A low threshold value generator is connected to the lower window comparator to supply a low threshold value to the lower window generator. The lower window comparator judges whether the pulse height width of the received sensor output signal from the voltage amplifier is more than the lower threshold value supplied from the low threshold generator. The differential voltage obtained from bridge will be in few milliVolts. After DC shifting the amplified signal will be less than upper window and greater than lower window. The amplified signal limit will be with in the middle of the window in absence of external magnetic flux.
[0048] During the application of magnetic field to the energy meter, the differential
voltage output from the Wheatstone bridge is more. The differential signal is DC shifted
to have swing of signal in both sides. The signal swings equally on both sides. The
Vcc
normal voltage level is . The swing is determined by direction of the magnetic flux.
If the direction of the magnetic flux is positive, then the swing is positive and vice versa. The Upper Window estimates the maximum field that may be allowed in positive

direction. The Lower window calculates the maximum field that may be allowed in a negative direction. The width of the windows may be changed to increase or decrease the sensitivity. The narrow the window, the higher is the sensitivity. The window with a wide width reduces the sensitivity of detection.
[0049] The window comparator always checks for the signal limit. If the magnitude of the swing of the signal crosses either the upper threshold limit or the lower threshold limit, the output of the window monitor will be high. In a permanent magnetic flux, the swing will be always on one side, as the direction of flux doesn't change with the time. On the contrary, the direction of magnetic flux changes with the time in an AC magnetic field. In such circumstances, the out put of the upper window comparator and the output of the lower window comparator are passed through an OR logic circuit device. The output of the comparator is ORed, i.e., the sensor output signal exceeding the limit in any one side (upper limit or lower limit) will be detected. The output of the OR logic circuit is passed through a level converter circuit.
[0050] The level converter circuit may be a resistive network. The out put of the OR circuit is converted so that the signal is within the acceptable range of the micro controller. Normally the output of the level converter is 5 volts, while the micro controller may receive a signal upto a level of 3.6 volts only. However this can directiy connected to 5V microcontroller also. Hence the output of the OR circuit is converted using the level converter and fed to a micro controller.

[0051] The micro controller detects the magnetic tamper detection event based on the received signal from the comparator through the OR logic circuit and the level converter. The micro controller records the detected magnetic tamper event with a time stamp on a memory such as electrically erasable programmable read only memory (EEPROM). The micro controller also calculates the duration of each magnetic tamper detection event. The micro controller calculates the number and frequency of the magnetic tamper events for recording on the computer for future reference and evidence. The memory may retain the stored magnetic tamper detection data for 100 years. Data can down loaded from Energy meter by attaching a meter reading instrument to the infra red (IR) port in the energy meter. The user computer installed with custom made software reports the detected magnetic tamper event to the user or Board of electric supply/ distribution company for further action.
[0052] The Microcontroller is part of the energy meter and the protective relay. The Energy meter may be a single phase meter or a three phase meter. The input to the micro controller is in digital format. The output Voltage from the comparator is divided using a resistive network for interfacing with a micro controller working with a voltage of 3.6V so that the micro controller ^.C operating at 5V and 3.6V can be interfaced with same hardware. When the high input signal is received at the micro controller, the micro controller starts the recording of the tamper detection event. The micro controller time stamps the starting as well as the ending of the magnetic tamper event to calculate the duration of each magnetic tamper event. The detected magnetic tamper event with time stamp is logged in permanent memory which has data retrieval period of lOOYears. The Maximum count of the event is programmable. The last-in-first-out is used. The stored

data may be downloaded from the Energy Meter for future evidence and proof of the event through the infra red (IR) port provided in the energy meter.
[0053] The micro controller is installed with an intelligent software to calculate and record the consumed electrical energy by assuming the maximum load current instead of actual consumption during a magnetic tamper event thereby penalising the consumer for malpractice. Thus the consumer is deterred from applying an external magnetic field to the meter and is punished to pay for maximum load instead of actual consumption. The micro controller calculates the actual consumption, when the external magnetic field is removed.
[0054] The micro controller activates a display device like Liquid Crystal Display (LCD) device to indicate the detected tampering of the energy meter due to magnetic field and the normal working condition of the energy meter. During the magnetic tampering event, a text "tanp," is displayed on the LCD device to indicate the detected tampering of the meter by an external magnetic field to alert the user. When the external magnetic field is removed, a text "no tanp", is displayed on the LCD device to indicate the normal working of the meter
[0055] The FIG.3 shows a flow chart explaining the method for detecting the tampering of an energy meter with an applied magnetic field. The meter is started to carry out the regular metering operations to compute the electrical energy consumed by a user. During the regular metering operations, the sensor will detect the presence of applied magnetic field. The variation in the resistors mixed with ferrous materials and arranged in the Wheatstone bridge network is calculated to detect the presence of an external magnetic field.

[0056] When the external magnetic field does not exist, the regular metering operations are continued and the results are recorded. On the contrary when the presence of an external magnetic field is detected by the sensor, the consumed electrical energy is recorded by assuming the maximum load current irrespective of actual load current by a micro controller. The same is recorded in the memory such as EEPROM. The magnetic tamper detection event is time stamped and stored in EEPROM for 100 years for referring at a future date. The sensor once again starts detecting the presence of external magnetic field. When the external magnetic field is not detected, then the meter starts executing the regular metering operations. When the external magnetic field is detected again, then the measuring of the maximum load current and the recording of the detected magnetic tamper event with a time stamp in EEPROM are continued by the micro controller until the sensor detects the external magnetic filed no longer.
[0057] The micro controller activates a display device like Liquid Crystal Display (LCD) device to indicate the detected tampering of the energy meter due to magnetic field and the normal working condition of the energy meter. During the magnetic tampering event, a text "tanp" is displayed on the LCD device to indicate the detected tampering of the meter by an external magnetic field to alert the user. When the external magnetic field is removed, a text "no tanp" is displayed on the LCD device to indicate the normal working of the meter.
[0058] Thus the present invention provides a detection system to prevent the tinkering of the energy meter with applied magnetic field reliably and cheaply. The system detects the magnetic field applied in any direction to improve the efficiency of magnetic tamper

detection process. The system detects the tampering of the energy meter by an applied magnetic field with high sensitivity. The system detects the magnetic tampering event reliably and accurately regardless of the intensity of the applied magnetic field. The rate of detection is independent of the magnetic flux. The system is able to measure both the steady and the alternate current magnetic flux applied on the energy meter. The system provides a permanent evidence for future investigation by storing the detection data in a memory for 100 years. The system counts and records the number of magnetic tamper detection events. The system stores the detected magnetic tamper detection event with a time stamp and the duration of each magnetic tamper detection event in the memory such as EEPROM. The system helps to stop the energy theft. During magnetic tampering event, the microcontroller calculates and records the consumed electrical energy by assuming the maximum load current irrespective of actual load current to punish the guilty customer. Thus the consumer is deterred from indulging in malpractice or applying an external magnetic field to the meter.
G) ADVANTAGES OF THE INVENTION
[0059] Thus the various embodiments of the present invention provide a detection system to detect the applied magnetic flux in any direction reliably. The system may detect the applied magnetic filed accurately irrespective of the rate of applied magnetic flux. The sensor uses a semiconductor material thereby reducing the cost of the system. The system is able to withstand high magnetic field reliably. The system may detect steady and alternate current magnetic flux accurately. The detection event is recorded on a memory. The detection event is time stamped and stored in memory like EEPROM.

The system may retain the detection data for 100 years. During magnetic tampering event, the microcontroller calculates and records the consumed electrical energy by assuming the maximum load current irrespective of actual load current to punish the guilty customer. Thus the consumer is deterred from indulging in malpractice or applying an external magnetic field to the meter.
[0060] Although the invention is described with various specific embodiments, it will be obvious for a person skilled in the art to practice the invention with modifications. However, all such modifications are deemed to be within the scope of the claims.
[0061] It is also to be understood that the following claims are intended to cover all of the generic and specific features of the present invention described herein and all the statements of the scope of the invention which as a matter of language might be said to fall there between.

CLAIMS
WHAT IS CLAIMED IS;
1. A magnetic tamper detection device for energy meter, comprising:
Sensor to detect magnetic filed applied on energy meter to output detection signal;
Microcontroller to receive comparison output detection signal from said sensor to notify, time stamp and to record tamper detection event;
Wherein said sensor comprises resistors mixed with ferrous materials so that resistance values of said resistors are changed with respect to applied magnetic filed on energy meter.
2. The magnetic tamper detection device according to claim 1, wherein said resistors are arranged in the form of a Wheatstone bridge network.
3. The magnetic tamper detection device according to claim 1, wherein said resistors provided in the opposite arms of the Wheatstone bridge network are arranged at 90 degrees to each other to detect magnetic field applied in any direction.

4. The magnetic tamper detection device according to claim 1, further comprises a voltage amplifier to receive said sensor out put signal and to amplify said sensor output signal.
5. The magnetic tamper detection device according to claim 1, further comprises a comparator to receive the amplified sensor output signal and to compare the amplified sensor output signal with preset threshold values to output a signal indicating the comparison result.
6. The magnetic tamper detection device according to claim 1, further comprises a threshold value generator to produce preset threshold values.
7. The magnetic tamper detection device according to claim 6, wherein the threshold value generator may be an upper threshold value generator to produce an upper threshold value.
8. The magnetic tamper detection device according to claim 6, wherein the threshold value generator may be a lower threshold value generator to produce a lower threshold value.
9. The magnetic tamper detection device according to claim 1, further comprises a level converter to convert the signal output from the comparator to levels that are acceptable by the microcontroller.

10. The magnetic tamper detection device according to claim 1, wherein the
microcontroller receives the level converted comparator output signal to detect a
magnetic tamper event.
11. The magnetic tamper detection device according to claim 1, wherein the micro
controller detects the magnetic tamper event, when the received amplified sensor
output signal at the comparator exceed either of the two generated threshold
values.
12. The magnetic tamper detection device according to claim 1, wherein the microcontroller records the detected magnetic tamper event along with a time stamp on a memory.
13. The magnetic tamper detection device according to claim 12, wherein the memory is an electrically erasable programmable read only memory (EEPROM).
14. A magnetic tamper detection method in energy meter, comprising:
Arranging resistive sensors mixed with ferrous material in Wheatstone bridge network to detect applied magnetic field;
Measuring the variation in resistance values with respect to the applied magnetic field to output a measurement signal;

Comparing the measurement signal with preset threshold values using a comparator;
Processing the comparator output signal with a microcontroller to detect a magnetic tampering event on energy meter.
Recording consumed electrical energy by assumimg maximum loads current during application of external magnetic field, and
Calculating actual consumption of electrical energy after removal of external magnetic field.
15. The magnetic tamper detection method according to claim 14, wherein the resistors provided in the opposite arms of the Wheatstone bridge are arranged in 90 degrees to each other.
16. The magnetic tamper detection method according to claim 14, wherein the resistance values of the resistors are varied with respect to the magnetic flux of the applied magnetic field.
17. The magnetic tamper detection method according to claim 14, wherein the
sensor measurement signals are clamped and amplified before forwarding to the
comparator.

18. The magnetic tamper detection method according to claim 14, wherein the
threshold value may be a lower threshold value produced with a lower threshold
value generator.
19. The magnetic tamper detection method according to claim 14, wherein the
threshold value may be an upper threshold value produced with an upper
threshold value generator.
20. The magnetic tamper detection method according to claim 14, wherein the
detected magnetic tamper event is time stamped by the micro controller.
21. The magnetic tamper detection method according to claim 14, wherein the
detected magnetic tamper event is stored in a memory along with the time stamp.
22. The magnetic tamper detection method according to claim 14, wherein the
detected magnetic tamper event is stored in an electrically erasable programmable
read only memory (EEPROM).
/