AnsweredAssumed Answered

Energy meter. Current Measurement Circuit

Question asked by aflamerich on Oct 23, 2012
Latest reply on Oct 23, 2012 by hmani

Hi hmani

 

Really my question is focus on the current measurement. It's clear for me that the differencial peak value must be + 500 mV to the ADEXXXX. No problem with that. What I'm care about is the voltage between a point measurement of the shunt and AGND. (See circuit below Vx-Vneutro = 110V aprox).  It is in my case 110VAC so the datasheet sais that it should not be more dan + 2V.

Is It really true?

We should put a transformer 1:1 or something?

 

Regards.

Alejandro

 

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Hi

 

There must an attenuation network attached between the line voltage and the chip so that the signal level at the chip inputs meets the given specification.

 

Also, for ADE7953, the max differential peak value that can be applied to input pins are + 500 mV and not + 2 V. Kindly refer to the specifications table on the datsheet. So if the line voltage is either 110 V or 220 V, your attenuation network must reduce the signal level to within + 500 mV differential for the ADE ICs to work properly. For current inputs, choose the value of the shunt resistor appropriately.

 

I also encourage you to post your future questions in public so that others might get benefited too.

 

Regards

hmani

 

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Hi

 

I'm design a Residential Energy Meter and I'm using a ADE7953. The voltage that go to home is 220VAC but in the house there are load in 110VAC and 220VAC so We need to measure two current, Phase Current and Nuetral Current.

If I use two shunt as current sensors I have a question about it.

 

the datasheet said (page 8, table 4)

 

Table 4. Parameter

Rating

VDD to AGND

−0.3 V to +3.7 V

VDD to DGND

−0.3 V to +3.7 V

Analog Input Voltage to AGND, IAP, IAN, IBP, IBN, VP, VN

−2 V to +2 V

Reference Input Voltage to AGND

−0.3 V to VDD + 0.3 V

Digital Input Voltage to DGND

−0.3 V to VDD + 0.3 V

Digital Output Voltage to DGND

−0.3 V to VDD + 0.3 V

Operating Temperature

Industrial Range

−40°C to +85°C

Storage Temperature Range

−65°C to +150°C

 

 

Vx-Vy and Vz-Vw <250mV and it is OK but

 

If you see in the circuit Vx, Vy, Vz, Vw with respect to AGND is around 110V so I dont know if this circuit is ok. But all of documentation circuits and Application note has circuit like this. So the table said no more than +/-2V.

 

De differential voltage is ok.

Common Mode is OK.

But as datashet sais IA,IAN, IB, IBN an VP to AGND should be max +-2V so this circuit this voltages are around 110V

 

Maybe I am understanding something wrong. Or maybe de design should be different?

 

Thanks for any comments o recomendations

 

Best Regards

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