This document defines and provides examples of different types of power meters, including electricity meters, wattmeters, optical power meters, cycling power meters, and Google Power Meter. It also explains some of the basic principles of how analog wattmeters and electricity meters work to measure electrical power.

1. RAJKUMAR A/L RAJENDARAN
LEENA A/P MUNIANDY

2. POWER METER may refer to :
Electricity meter - measures electrical energy (electrical
power supplied to a residence, business or machine over
time)
Wattmeter - measures the electrical power circulating in
any electric circuit
Optical power meter - measures energy in an optical
signal
Google Power Meter – is a tool to track a household’s
energy usage
A cycling power meter – measures the power output of a
bicycle rider

3. • Electric power is the rate at which electric energy is
transferred by an electric circuit.
• The SI unit of power is the watt.
• When electric current flows in a circuit, it can transfer
energy to do mechanical or thermodynamic work.
• Device convert electrical energy into many useful forms
such as, heat (electric heaters), light (light bulbs), motion
(electric motors), sound (loudspeaker), information
technological processes (computer), or even chemical
changes.

4. • A meter for measuring the amount of electric power used.
• Some examples of power meter are:
Wattmeter KWH meter Clamp meter

5. • Symbol of analogue wattmeter
• Basic Principle of Analogue Wattmeter
A wattmeter has two coils that multiply volts times amps.

6. • One coil is wired as an ammeter with a shunt, the other as
a voltmeter with a multiplier.
• This instrument is of the electrodynamic type.
• It consist of a pair of fixed coils, known as current coils and
movable coil known as the potential coil.
• The voltage is measured across (parallel) the load and
charges the pointer magnet.

7. • The current is measured in series with the load and
charges the field magnets.
• The movable coil carries a needle which moves over a
suitable marked scale.
• Spiral coil springs hold the needle to a zero position.
Fig1: A simplified electrodynamic wattmeter
circuit

10. • An electric meter or energy meter is a device that
measures the amount of electrical energy consumed by a
residence, business, or an electrically powered device.
• Electric meters are typically calibrated in billing units, the
most common one being the kilowatt hour.
• The most common type of electricity meter is the
electromechanical induction watt-hour meter.
• The electromechanical induction meter operates by
counting the revolutions of an aluminium disc which is
made to rotate at a speed proportional to the power.

11. • The metallic disc is acted upon by two coils.
• One coil is connected in such a way that is 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.
• A permanent magnet exerts an opposing force proportional to
the speed of rotation of the disc. The equilibrium between
these two opposing forces results in the disc rotating at a
speed proportional to the power being used.

12. • An electrical meter with integral AC current clamp.
• This allows properties of the electric current in the
conductor to be measured, without having to make
physical contact with it.
• Clamp meters are often sold with a device that is plugged
in between the power outlet and the device to be tested.
The device is essentially a short extension cord with the
two conductors separated.

13. Leakage current measurement basics
Leakage current most commonly flows in the insulation surrounding
conductors and in the filters protecting electronic equipment around the home
or office. So what's the problem? On circuits protected by GFCIs (Ground
Fault Current Interrupters), leakage current can cause unnecessary and
intermittent tripping. In extreme cases, it can cause a rise in voltage on
accessible conductive parts.

14. • Insulation has both electrical resistance and capacitance –
and it conducts current through both paths. Given the high
resistance of insulation, very little current should actually leak.
But -- if the insulation is old or damaged, the resistance is
lower and substantial current may flow. Additionally, longer
conductors have a higher capacitance, causing more leakage
current. That's why GFCI breaker manufacturers recommend
one-way feeder length be limited to 250 feet, maximum.
• Electronic equipment, meanwhile, contains filters designed to
protect against voltage surges and other disruptions. These
filters typically have capacitors on the input, which adds to the
overall capacitance of the wiring system and the overall level
of leakage current.

15. • When the load is connected (switched on), the leakage current measured
includes leakage in load equipment. If the leakage is acceptably low with
the load connected, then circuit wiring leakage is even lower. If circuit
wiring leakage alone is required, disconnect (switch off) the load.
• Test single-phase circuits by clamping the phase and neutral conductor.
The measured value will be any current flowing to ground.
• Test three-phase circuits by clamping around all three-phase
conductors. If a neutral is present, it should be clamped along with the
phase conductors. The measured value will be any current flowing to
ground.

16. Measuring leakage current through the ground conductor
• To measure the total leakage flowing to the intended ground connection, place the
clamp around the ground conductor.
Measuring leakage current to ground via unintentional paths to ground.
• Clamping phase/neutral/ground together identifies imbalance current that represents
leakage at an outlet or electrical panel via unintentional paths to ground (such as the
panel sitting on a concrete base). If other electrical bonding connections exist (such as a
connection to a water pipe), a similar imbalance may result.

17. Tracing the source of leakage current
• This series of measurements identifies the overall
leakage and the source. The first measurement can be
made on the main conductor to the panel. Measurements
2, 3, 4 and 5 are made subsequently to identify circuits
carrying the larger amounts of leakage current. j k l m n

18. • Summary
Leakage current can be an indicator of the effectiveness of insulation
on conductors. High levels of leakage current may be present in
circuits where electronic equipment with filters is used, and can
cause voltages that disrupt normal operation of equipment. It is
possible to locate the source of leakage current by using a low
current leakage current clamp to take methodical measurements as
described above. If necessary, this enables you to re-distribute loads
around the installation in a more balanced way.

19. • Step 1
Turn on the clamp meter and set the function for measuring current. A
selection knob or button to select whether we are measuring alternating
current (AC) or direct current (DC) flow. Most household electric
devices use household voltage from an outlet, which will be AC current.
• Step 2
Clamp the meter onto the power cord. The ends of the clamp meter
arms, which resemble pinchers, will have a recessed area through
which the power cord should be placed. Ensure that the clamp meter
arms are stable with the cord between them.

20. • Step 3
Read the current flow on the clamp meter display. Most clamp
meters have automatic range finders, but if it does not, increase
the range of the meter until get a reading. Write down the
reading, which will be numbers that represent the amount of
amperes, or amps, flowing through the cable.
• Step 4
Measure the amount of current flow through an appliance
(washing machine) by turning it on and having it perform its
functions. The current flow will be much higher when the
appliance motor is turning. For a refrigerator, turn down the
thermostat to turn on the cooling action, which will increase
current flow.
• Step 5
Adjust the position of the clamp meter to ensure we are getting
accurate current flow readings.
• Step 6
Remove the clamp meter from the power cord

21. Optical power meter Cycling power meter
A cycling power meter is a device on
a bicycle that measures the power output
of the rider. Most cycling power meters
use strain gauges to
measure torque applied,
and, combined with angular velocity,
calculate power. The technology was
adapted
to cycling in the late 1980s and was tested
in professional bicycle racing
An optical power meter (OPM)
is a device used to measure the
power in an optical signal.

22. • Google PowerMeter was a software project of Google's
philanthropic arm, Google.org, to help consumers track their
home electricity usage. The development of the software was
part of an effort by Google to invest in renewable
energy, electricity grid upgrades, and other measures that
would reduce greenhouse gas emissions. It was launched on
October 5, 2009 and ended on September 16, 2011.
• The software was designed to record the user's electricity
usage in near real-time. According to the company, if half of
America's homes' energy use was cut by ten percent, it would
equal the average energy used by eight million cars.

23. • https://www.google.com/#q=summary+of+chapter+5+po
wer+meter%2FEE101+Measurement
• http://mysya01.files.wordpress.com/2012/04/power_mete
r.pdf
• http://en.wikipedia.org/wiki/Electricity_meter