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# Energy meter problems

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#### hafizimran18

##### Member level 4
I AM WORKING ON 'SINGLE PHASE ENERGY METER' ,i have a lot of i.c for that purpose but each of them needs only mV on their analogue input channels,, how can i acheive such a small voltage from 220VAC and i also think that there would be a loss of major information when stepping 220V down to mVolts,, it can be disturbed even by thermal noise,, please suggest me suitable solutions if you can...........

Which inputs are you referring to, the voltage or the current?

You can step down the voltage with ether a resistive voltage divider or a small transformer.

Thermal noise is usually lower than millivolts.

I suggest you try it out first with a transformer. It will not be as bad as you have imagined.
Which IC are you using that accept mV?

I AM WORKING ON 'SINGLE PHASE ENERGY METER' ,i have a lot of i.c for that purpose but each of them needs only mV on their analogue input channels,, how can i acheive such a small voltage from 220VAC and i also think that there would be a loss of major information when stepping 220V down to mVolts,, it can be disturbed even by thermal noise,, please suggest me suitable solutions if you can...........

Try to create a circuit with the help of Ic's it will help you a lot in that purpose.

I AM WORKING ON 'SINGLE PHASE ENERGY METER' ,i have a lot of i.c for that purpose but each of them needs only mV on their analogue input channels,, how can i acheive such a small voltage from 220VAC and i also think that there would be a loss of major information when stepping 220V down to mVolts,, it can be disturbed even by thermal noise,, please suggest me suitable solutions if you can...........

What IC exactly, and can you describe that mV range? Often ADC inputs are in range of several Volts up to 5V.

There is lots of energy metering projects.

You can use dedicated power metering IC for this, or uC with user code. For sensors you can use current transformer, hall sensor,...

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Do you plan to take signal-impulse from energy metering counting device or you want to sense from cable?

What IC exactly, and can you describe that mV range? Often ADC inputs are in range of several Volts up to 5V.

There is lots of energy metering projects.

You can use dedicated power metering IC for this, or uC with user code. For sensors you can use current transformer, hall sensor,...

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Do you plan to take signal-impulse from energy metering counting device or you want to sense from cable?

i am using ade7757 energy meter i.c,, i think i was wrong and it can take -6V to +6V ,, can somebody verify it from its datasheet for me please????

i am using ade7757 energy meter i.c,, i think i was wrong and it can take -6V to +6V ,, can somebody verify it from its datasheet for me please????
The V1 channel, which reads the current shunt voltage, has a maximum linear input of 30mV.

The V2 channel, which reads the voltage, has a maximum linear input of 165mV.

Both inputs can take ±6V without damage.

Look at the table on page 5 of the data sheet. Look at Figure 2 for a typical configuration.

The V1 channel, which reads the current shunt voltage, has a maximum linear input of 30mV.

The V2 channel, which reads the voltage, has a maximum linear input of 165mV.

Both inputs can take ±6V without damage.

Look at the table on page 5 of the data sheet. Look at Figure 2 for a typical configuration.

it mean i can use my 220V to 5V transformer for it,, right??

it mean i can use my 220V to 5V transformer for it,, right??
You can if you reduce the 5V to a maximum of 165mV peak voltage at the V2 input with a resistive divider.

What you want to measure power or voltage ?

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Current Transformer is different thing from standard transformer.

What you want to measure power or voltage ?

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Current Transformer is different thing from standard transformer.

i am using it for energy meter,, my purpose is energy measurement

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thats good, but i want to use 5V as it is ,, i don't want to reduce it,, should i do so or not ??

Yes, but in your post #10 you mention 220V to 5V transformer, with that you can measure voltage, not power. You need to use some way for current sensing, such as current transformer, hall sensor, shunt resistor.

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See another example with ADE7757:

http://educypedia.karadimov.info/library/Low Cost Energy Meter.pdf

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Both examples uses shunt resistor to sense current. Power supply voltage of 5V for IC is made by reducing voltage with unipolar capacitor and resistor (transformeless psu).

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I will use c.t to sense curent,, is that good??

Yes it is.

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thats good, but i want to use 5V as it is ,, i don't want to reduce it,, should i do so or not ??
Yes you must reduce the voltage. If you look in the data sheet you will see that the maximum V2 input voltage for normal operation is 165mV peak. You can input 5V without damage but the circuit won't give the proper power output value, which I assume is what you want.

Yes you must reduce the voltage. If you look in the data sheet you will see that the maximum V2 input voltage for normal operation is 165mV peak. You can input 5V without damage but the circuit won't give the proper power output value, which I assume is what you want.

hello im doing a similar project which has ade7756 a pic microcontroller and then wireless transmission..... . . .

hello im doing a similar project which has ade7756 a pic microcontroller and then wireless transmission..... . . .

i am also doing same,,, where are you from??? email me at hafizimran18@yahoo.com,,,

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