We can consider this question to be the sequence of this previous one.
Now I'm working on the current and voltage acquisition part (red marker) of the CS5463 (datasheet).
The CS5463 is an integrated power measurement device which combines two analog-to-digital converters, power calculation engine, energy-to-frequency converter, and a serial interface on a single chip. It is designed to accurately measure instantaneous current and voltage, and calculate VRMS, IRMS, instantaneous power, apparent power, active power, and reactive power for single-phase, 2- or 3-wire power metering applications.
First of all, one question about the spec:
- The datasheet page 16 contains: "the full-scale differential input voltage for the current and voltage channel is +/-
250 mV". From this, I assumed this channels can receive voltages from
250mV, and the reference for this values is the AGND pin. Am I right? (This information is kid of confirmed on pages 7 and 8.)
About the circuit itself, this time, I'm having more trouble to figure it out. My intuition says it's a simple voltage divider to measure the voltage and a high power resistor (shunt) to measure the current. The circuit is almost that, but I don't know the purpose of the extra components. And without knowing it, I can't define their values correctly.
First question: why all the circuit considers the "line" as the ground and not the "neutral"? This way, all the waves are inverted to the originals. What's the advantage of doing this?
What happens if I plug it inverted, in a way that the IC's "neutral" connects to the "line" of the outlet and vice versa?
The R1 and R2 is a voltage divider block. The peak voltage in my region is 311V (220V RMS). Aiming for a 250mV peak, I chose the values
12.4 kohms(if this last one doesn't exist, I'll put an approximate one or some resistors in series).
The shunt resistor may be of
25 ohms. If a maximum current of
10Apasses through it, it'll dissipate
2.5Wand generate a
mVshould I leave as a safe range in this case? These values can be rezised to leave a safe range of
50mVabove and bellow the waveform.
The remaining components:
- I can't identify their purposes. So, I can't size them correctly. The
Cv+capacitor has the grounds between its terminals, so what's it goal? This capacitor and the
Rv-resistor appear to be a RC filter. But I've never seen one plugged on the ground. The
Cvdiff… I have no idea what they do. I can say the same for the equivalent components of the current sampling circuit, which also has the
Ri+resistor (without an analogue component on the voltage circuit).
The questions are scattered all over the question, but any doubts you have I try to summarize here below.