TITLE: AN IMPROVED ENERGY METER
FIELD OF INVENTION
The present invention relates to an improved energy meter with a battery power saving and tamper proof feature.
This present invention is directed towards a method to enhance the battery life of an energy meter during storage and transportation approximately from just 12 months to > 15 years.
Prior Art and Background
Conventionally, an energy meter is an electrical measuring device, which is used to record electrical energy consumed over a specified period of time in terms of units.
Energy meter is basically an assembly of electrical and mechanical components. The design of energy meter depends upon which rating of current and voltage upon meter has to work. The components like potential coils and current coils are to be designed in accordance with customer's requirements. Other components like, power supply, metrology circuitry, processor, memory, communication ports and LCD display are to be designed accordingly. All these components are fixed in a housing and connection to be made as per circuit designed.
Generally, energy meters are provided with a battery which is utilized by the controller in sleep mode drawing power during Storage and Transportation (i.e. Shelf Life) and power outage conditions. The power drawn from this battery is utilized to display the data stored in the system on the LCD screen with a press of button. The Battery power is also required to detect unauthorised opening of the meter Top cover for the purpose of tampering the meter.
It has been observed that due to irregular or situational power consumption, during conditions like ESD (Electro Static Discharge), stationary or sleep mode conditions like storage and transportation, the life of the battery in the said meters gets drained / exhausted quicker than usually expected / calculated due to the controller entering an undefined, high current consuming state. In addition, a common problem among energy meters, are that they are tamper prone (e.g. opening of the top cover to change the measurement circuit inside) and is in constant need of a viable tamper proof feature.
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In view of the above shortcomings, the energy meters currently consume high power from the battery. This high consumption power from the Battery makes the conventional energy meters costly and commercially unviable.
As discussed, another common problem with these energy meters is that they are tamper prone The Energy thieves open the meter and change the measurement components inside to make the meter slow. Hence if the meter is smart to detect and register the attempt of opening the meter cover with time and date, the defaulters can be caught with the evidence. This Anti tamper feature requires the meter's controller to automatically boot up on battery, triggered by the cover opening event and go back to shutdown mode automatically after registration of tamper event.
Certain conventional steps taken in order to improve Battery life are:
• Battery mAH is increased to prolong life of the battery resulting in the increase in the size of battery and cost.
• Two battery solutions are used one for external RTC and other for Microcontroller Sleep Mode operation, need more space to accommodate extra battery and also increase the cost.
In the past, several practitioners have attempted to enhance the life of the battery, thereby saving power. In addition, efforts have been made in order to reduce tampering activity of the energy meter, thereby reducing erratic readings.
Some of the relevant prior arts wherein such attempts to improve battery life as well as bring in tamper correction features are made are as below.
As for relevant literature on the tamper proof feature, EP 91304102, teaches an apparatus and method is disclosed for measuring the consumption of electricity from a mains supply which is either single or multi phase. The apparatus and method of the invention is also able to detect when tampering with connections to the supply ocuurs as for instance, may be done in an attempt to reduce the quantity of energy regisetered as having been used. In a meter which takes as inputs signals indicative of the voltage and currents present in the supply a tamper is registered whenever the voltage reading , for instance in one phase of the three -phase
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supply, is absent while the corresponding current is present. If both the voltage and current are absent this is not registered as tampering but may be noted as a fault in the system.
EP 81300419, teaches an electricity meter for metering the amount of electrical energy supplied by a power consumer is provided with means for detecting unauthorized attempts to gain access to the interior of the meter. The detecting means typically comprises an optical path or an electrically conducting path which is arranged to be broken by such attempts. In one embodiment, the path is formed by a filamentary member used to seal a bolt holding on the meter case or cover, while in another embodiment, the path is broken by the removal of the meter cover or the terminal block cover. In either embodiment, a further path may be formed in or on the surface of the meter cover so as to be broken if the cover is broken or drilled.
WO 2011004336 discusses tampering with an electricity network is detected from an electricity meter by transmitting a probe signal over at least part of the electricity network from a signal source in the electricity meter. A reflected signal produced by reflection of the probe signal in the electricity network is received back. The reflected signal is comapared with a reference signal. An alarm signal is generated when said comparing detects a deviation between the reflection signal and the reference signal, in particular when reflections from a new position on the electricity network near the electricity meter are detected.
The estimated power consumption of the Energy Meter in Sleep Mode "During Storage and Transportation (i.e. Shelf Life) is around 80 micro-amperes, with this rate of consumption a battery of lOOOmAH will drain out in period of just 12 months. Thus, this hampers the battery life to a great extent. To overcome this problem a battery of higher power can be used, but this makes the whole process expensive and hence not advisable. Moreover, the increased battery size will require a redesigning of whole of the circuit and mechanical plastics casing which is used in Energy Meter.
In view of the above drawbacks and the shortcomings of the above features of convention energy meters, the Inventors have attempted to develop the state of the art towards power saving of the battery as well as introducing a tamper proof feature in the energy meter. The instant invention is explained in the description as illustrated herein supported by necessary illustrations and working protocols.
Objective of the Invention
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The objective of the present invention relates to an improved energy meter with a power saving and tamper proof feature.
Another objective of the present invention relates to a method to enhance the battery life of an energy meter in sleep mode approximately from just 12 months to > 15 years.
Description of the Invention
Energy meter is a device that measures the amount of electric energy consumed by an electrically powered device.
The proposed invention primarily meant for improving the EM5400 Energy Meter by increasing the battery life and equipping it with more reliable tamper proof feature.
One of the essential features of the energy meter is the Battery. The power through the battery is drawn on to display the data which is stored in the system on the LCD Screen with the press of button provided for this purpose during the Sleep mode i.e. during Storage and Transportation (i.e. Shelf Life) and power outage conditions.
While the system is ON during displaying the stored data, it consumes power which is drawn from battery. Thus, this imposes a huge load on battery and shreds away the battery at higher rate as the power consumed is very much.
The present invention intends to take away the load of the battery while system performs the job of displaying the stored data on LCD screen and hence in this way the life of the battery is enhanced.
The present invention introduces a device called 74HC221 which has Dual Single Trigger Mono Stable Multivibrator which carries out the desired job of lessening the battery load and thus increasing the life of battery.
The present invention relates to an improved energy meter with a battery power saving feature as a tamper proof feature.
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Further, the present invention relates to a method to enhance the battery life of an energy meter in sleep mode approximately from just 12 months to > 15 years. At the same time it also prevents the heavy drainage of the battery when the controller in sleep mode goes into an undefined state (e.g. ESD, tamper) consuming heavy current from the battery
Before this invention Energy meter was consuming 80uA with lOOOmAH Battery.
Current Consumption 80uA = lOOOmAH / 0.08ma = 12500 Hours
12500 Hours 7 24 = 520 days
520days 7 31 = 16 months (But in actual we will get only 12Months as battery discharges
itself small amount of power from the time it is manufactured to time it is used).
After this invention Energy meter was consuming 1.5uA with lOOOmAH Battery.
Current Consumption 1.5uA = lOOOmAH / 0.0015 ma = 666666.7 Hours
666666.7 Hours / 24 = 27777 days
27777 days / 31 = 896 months
896 months /12 = 74 Years
At 1.5uA Battery consumption will give 74 years. For all practical purpose we have taking
for greater than 15 years, as there will be self-discharges of the Battery of 2% to 4% every
year due to possible decomposition of the chemical contents, occurrence of the unwanted
chemical or physical changes to, or the loss of, the active materials in the battery.
Temperature etc...
The present invention relates to a system for power saving of battery in an energy meter. The present invention is also a successful attempt to introduce top cover tamper proof feature in (0.2 Class Energy Meter).
Other Classes are class 0.5 and class 1 Energy Meters
The sleep mode circuit as referred herein Fig 1. said sleep mode circuit comprising of-
(1) Mains Power Supply
(2) Battery.
(3) P- Channel MOSFET
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(4) Micro Controller
(5) 74HC221 which has Dual Single Trigger Mono Stable Multivibrator
(6) External RTC
(7) Memory, LCD and other CKT
The power through the battery is drawn on to display the data which is stored in the system on the LCD Screen with the press of button provided for this purpose.
The instant invention relates to a method in which Dual Single Trigger Mono Stable Multivibrator is used to regulate the power consumption through battery during Storage and Transportation (i.e. Shelf Life) and power outage conditions. Further, any Dual Complementary-symmetry Metal-Oxide- Semiconductor (CMOS) Single Trigger Mono Stable Multivibrator with less than 2uA current consumption in quiescent state, may be preferable.
The instant invention utilizes a method by which the battery life during storage and transportation (i.e. Shelf Life) and as well as during power outage conditions is enhanced. The present invention is applicable to batteries of a wide range of voltages, for ex. 3.6 V.
The invention relates to a system for power saving enabling RTC sleep feature with top cover tamper proof in EM5400 (0.2 Class Energy Meter), where the invention envisages an improved process for power saving and tamper proofing.
The function of the Mono stable Multivibrator is to generate multiple vibrations of desired frequency, which turns ON the micro controller and MOSFET. The power will be drawn from battery only by External RTC and Single Trigger Mono Stable Multivibrator which is less than 1.5 Micro - amperes. Hence, Mono stable Multivibrator takes off the pressure from the battery thus increasing battery life.
The proposed invention is depicted in the accompanying drawing in order to illustrate the invention.
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The illustration shown in drawing is only representative to show the invention. The invention is proposed to work in following said manner.
During Storage and Transportation (i.e. Shelf Life) and power outage conditions, the system i.e. the energy meter is not in use and hence, it is in OFF stage.
At this time only External real time clock (RTC) and Single Trigger Mono Stable Multivibrator will be drawing current from the battery which is less than 1.5 Micro- amperes.
When the button is pressed to display the stored data on LCD screen, the multivibrator will trigger a pulse of around 6 seconds which will cause driving of MOSFET. Simultaneously the Micro Controller will boot up in low power mode. The power drawn by the Micro Controller to boot up will be supplied from battery but it would be around 12mA which is very less. The time required by the Micro Controller to boot up will be around 2.5 to 3 seconds.
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Once Micro Controller boots up, it takes control of MOSFET and sends CLR signal to Multi Vibrator to disable it. Then the Micro Controller turns ON the external peripherals. Subsequent to this, the Micro Controller will display and scroll the data required on the LCD for about 8 seconds.
If no button is pressed during this ensuing time of about 8 seconds the system will shut down.
If the stored data is required to be displayed subsequently, the button will be required to be pressed again. As a result of the whole arrangement of the circuit as executed and as described in the preceding paragraph, considerable amount of power of the battery is saved.
Top Cover Tamper Proof:
The instant invention also relates to equip the energy meter with a tamper proof feature. The Single Trigger Mono Stable Multivibrator is utilized for this purpose as well. The Multivibrator package contains Dual Non - Retriggerable Mono Stable Multivibrator, of which one set is used in Battery Power Saving Circuit and other is used here as tamper proofing the top cover.
Dual non-retriggerabie monostable Multivibrator in single Package
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