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Help with registers ADE7753, Urgent

Question asked by JuanTV on Apr 27, 2018
Latest reply on May 15, 2018 by Gary.Kang.AnalogDevices

Hello everyone,

I have created an energy meter with the ade7753 and using ACS712 of 20 A as current sensor (in my application I will only measure up to 750W), the schematic can be seen below, in my application, I am not using the CF pin (since I do not have a reference meter). The MODE register is at its default value (0x000C), I do not use interruptions, I simply base myself on the schematic of the data sheet.

The communication with my uC (microcontroller) is fine, I can also read the values of the registers of VRMS (0x17), IRMS (0x16), and Energy (0x02).

 

My question is: How do I convert the data I am reading to physical values? for example, the value of the VRMS register (0x17) that is an unsigned integer convert to volts, or the IRMS register (0x16) to amperes.

According to the data sheet, on page 23, the ADC code for channel 1 (IRMS) and channel 2 (VRMS) is:

 Code (ADC) = 3.0492 * (Vin / Vref) * 262144

 

then in the case for channel 1, on page 25 Channel 1 RMS calculation section, it says that:

"The conversion from the register value to amps must be done externally in the microprocessor using an amps / LSB constant. To minimize noise, synchronize the reading of the rms register with the zero crossing of the voltage input and take the average of a number of readings".

How do I get that amps / LSB constant?

 

then for channel 2 (VRMS) on page 26 Channel 2 RMS calculation section ,it says:

"The conversion from the register value to volts must be done externally in the microprocessor using a volts / LSB constant. Since the low-pass filtering used for calculating the rms value is imperfect, there is some ripple noise from 2ω term present in the rms measurement "

Like the previous one how do I get that constant of volts / LSB?

 

How would you do for the Energy Register? What is the constant of Wh / LSB?

 

I repeat: I do not have a reference meter or an accurate source and I am unable to perform the calibration process as indicated in the datasheet ,its a college application.

 

I would appreciate your help, since I am not very good at reading in English and maybe there is something I am omitting in the data sheet.

 

Regards,

Juan

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