# Energy Meter

Thread Starter

#### devgorkha

Joined May 17, 2010
29
how does the energy meter work? how can we measure current and voltage for any load?

#### crutschow

Joined Mar 14, 2008
27,177
The meter takes many simultaneous and instantaneous samples of the voltage and current over each waveform cycle. Each voltage and current sample is multiplied together to get the instantaneous power value. These values are then averaged over the waveform period to get the average (RMS) power.

• devgorkha

#### samin

Joined Oct 14, 2011
32
In energy meter there are 2 CT's are used.
One for recording current through incoming phase and other through outgoing phase .When the load is ON on outgoing side the current flowing through both CT's is compared by electronic circuit. An watt-meter is calibrated as per standards which measures wattage proportional to current.

#### crutschow

Joined Mar 14, 2008
27,177
In energy meter there are 2 CT's are used.
One for recording current through incoming phase and other through outgoing phase .When the load is ON on outgoing side the current flowing through both CT's is compared by electronic circuit. An watt-meter is calibrated as per standards which measures wattage proportional to current.
You only need one CT. The current out of the meter is the same as the current going into the meter (where would any difference current go?). Thread Starter

#### devgorkha

Joined May 17, 2010
29
Does it measure only current consume? or the measure current is multiply with voltage of instantaneous time period to get watt.
the current is measured by ct. what about the measuring of voltage?
Is there any ready-mad component to measure power?
And i am confuse about digital and analog energy meter, does these have same working principle?

#### Lundwall_Paul

Joined Oct 18, 2011
228
There are some good products on the market to measure your house power. I use the TED-5000.

More on measuring power.

You must take two readings to measure power. The current you have the current loops the second would be using a volt meter. By measuring current and voltage you can come up with the KVA (Kilo volt amps). NOT to be confused with KW (Kilo-watts)
The difference between KW and KVA is the power factor. KVA*Power factor is KW. The power factor comes from a phase difference between volts and current. Typically from an inductive loads like a motor or power supplies.

Better explanation of power factor check out http://www.energymanagertraining.co...cal_measuring/how to measure power factor.htm

Thread Starter

#### devgorkha

Joined May 17, 2010
29
I understand about pf and kw. how can we calculate pf in our project energy meter?
In our project we measure current by current transformer and voltage by using voltage drop in resistor. the problem is to multiply VA term by power factor for measuring KW.

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