I want to interface the following CT to Arduino:
So I have the following data:
- Primary Current: 600 Arms
- Secondary current: 5 Arms
- Burden: 2 VA
Burden = 2 VA means that:
Rmax = P/I^2 = 2/25 = 0.08 Ohms max burden resistor (am I right?)
At 5A, there should be a voltage drop of V = P/I = 2/5 = 0.4 Vrms
Let's say that Rburden = 0.05 Ohms:
Pmax = 5^2 * 0.05 = 1.25W.
0.05 Ohms/3W is available on the market, so I'd go for it.
Given Rburden = 0.05 Ohms, at 5A we have Vdrop = 0.05*5 = 0.25 Vrms or 0.35 Vpeak.
So the output voltage at the burden resistor will range from 0 to 0.35V. I want to map this range from 0 to 4V for the Arduino's ADC.
I have decided to bias the signal at 2.5V as follows:
This means I will have a max differential voltage of Vdiff = 4-2.5 = 1.5V. I would want the Arduino to read 4V at 5A.
A non-inverting amplifier will be suitable for this case. Calculating the gain resistors I get R3 = 10K and R4 = 33k. See output waveform below:
To sum up, these are my questions:
- Would this approach work properly? Do I need to add some filtering or adjust something in the current design?
- This approach uses the DC bias principle, but another approach is to use a precision rectifier. Which one would perform better?