The three phase digital energy meter works by sensing the voltages and currents of each phase using sensors. The sensed voltages and currents are converted to digital using an A/D converter. The processing and communication unit then calculates various derived quantities from the digital values and interfaces with other modules. It stores accumulated energy values in memory, which can be read even during power failures. Digital meters use communication protocols to allow for remote and automatic meter reading without needing a physical meter reader.

1. THREE PHASE DIGITAL
ENERGY METER
• The demand readings stored with the profiles accurately
indicates the load requirements of the customer
• This load profile is processed at the utilities for billing
and planning purposes
INTRODUCTION
• Digital meter use low power radio,GSM, Bluetooth,As well as RS-485 wired link

2. CONSTRUCTION:
• The block diagram of Three phase digital Energy meter is as shown in
figure
• The meter consists of voltage and current sensors,a processing and
communication engine(micro processer),a temperature sensor,a
memory,and other modules such as LCD display,communication ports/
modules and so on.
• The meter is given the voltage and current inputs and has a voltage
reference,samplers And quantizes Followed by an Arc section to yield the
digitalised equivalents of all the inputs.
• These inputs are then processed using a digital signal processor (dsp) to
calculate various metering parameters such as powers, energies etc
• Digital meters have an electronic watt transducer which is a solid-state
circuit that performs the multiplication of current and voltage signals and
delivers an output in the of a Pulse train At a rate proportional to power

3. BLOCK DIAGRAM

4. WORKING
• When the three phase supply is applied to it the voltage is sensed by voltage sensor and current is
sensed by current sensor.
• the voltages and currents of each phase are sensed by the sensors
• These sensed voltages are converted into digital by using A/D converter.
• The processing and communication unit responsible for calculating the various derived quantities
from digital values generated by the meter
• These unit also responsible for using protocols and interface with other add on modules connected
• A digital energy meter consists of power measuring circuit which measures power and generates the
pulses proportional to the power

5. WORKING
• A digital meter consists of power measuring circuit which measures the power and generates
the pulses proportional to the piwer
• A counter device counts the each of the pulses generated by the power measuring circuit
The output of the counter is displayed in the display device In digital nemara
• The digital energy meter utilising a counter device counting the pulses generated in
proportion to the power to be measured.
• The accumulated energy values are stored in memory device and can be read even during the
power failures
• Digital meter uses RS-485 wired link for communication purpose between various devices
• AMR(AUTOMATIC METER READING) And remote meter reading (RMR) technologies are
employing today,that allows metervto be checked without the need to send a meter reader
out.

6. ADVANTAGES
• Single and three phase both are available with 6;digit coumter
• Current reversal indication is privided
• LED indication is accurate
• Rugged construction,dust proof body,elegant polycarbonatr counter
• Not effected by external magnetic firld
• Not effected by mounting position

7. DIGITAL FREQUENCY METER
• Introduction:
The frequency of a unknown signal can be measured by
digital frequency meter
Principle of working:
• The signal whose frequency is to be measured is converted
into train of pulses.on epulse for each cycle of the signal

8. WORKING OF DIGITAL FREQUENCY METER:

9. WORKING
• When an unknown frequency signal is applied to the meter it passes on
to amplifier which amplifies the weak signal. Now the amplified signal is now applied
to Schmitt trigger which can convert input sinusoidal signal into a square wave.
• The oscillator also generates sinusoidal waves at periodic intervals of time, which is
fed to Schmitt trigger.
• This trigger converts sin wave into a square wave, which is in the form of continuous
pulses, where one pulse is equal to one positive and one negative value of a single
signal cycle.
• The first pulse which is generated is given as input to the gate control flip flop turning
ON AND gate. The output from this AND gate count decimal value. Similarly, when the
second pulse arrives, it disconnects AND gate, and when the third pulse arrives the
AND gate turns ON and the corresponding continuous pulses for a precise time
interval which is the decimal value is displayed on the counter display

10. INTRODUCTION TO CLAMP METER (TONG
TESTER)
• Tong tester is an electrical device used to read
the magnitude Of current in an conducted or
cable
• It is very convenient testing instrument
• It is also known as clamp meter or clamp on
meter

11. CONSTRUCTION
• It consists of two jaws which open to
• allow clamping around an electrical conductor
• This allows to measure current in the conducte
Withoutt having to make physical contact with it
• For electricians ,a clamp meter is a quick and versatile
Instrumentt

12. ADVANTAGES
• It permits current measurement on live
conducted without circuit interruption.
• Using clamp meter,current can be measured
by simply clamping live conductor
• One of the benefits of this method
• is that,large currents can be measured without disturbing load

13. WORKING
• While making current with an multy meter ,
measurement;it depends ,it needs to cut and
connect the instrument
To the circuit under test

14. TYPES OF TONG TESTERS
• Two types of tong testers are available in the market
Namely analog tong tester and digital tong tester respectively.
• Analog tong testers indicates the current to be measured by
deflecting the pointer ,
• Whereas digital tong testers gives reading on the digital display.
• The DC currents and low and current are difficult to measure with
the tong tester

15. USES OF TONG TESTER
• Tong tester used to measure leakage currents in the cables up to
10 micro amps
• Used to measure low currents
• High AC currents are easily measured
• It can be used as a multi meter
• It is also used to measure capacitance ,temperature, frequency
etc...

16. COMPARISON BETWEEN DIGITAL AND ELECTRO
MECHANICAL INSTRUMENTS
Digital instruments
1. Accuracy is high
2. The construction is complex
3. It has no moving parts
4. Power consumption is less
5. Cost is high
6. These are free from parallax error
and approximation errors
Electro mechanical instrumnet
1. Accuracy is less
2. The construction is simple
3. It has moving parts
4. Power consumption is less
5. Cost is less
6. These give considerable parallax
and approximation errors