but the problem is, i do not have any idea how to start. can any one help please?
*Safety approval: TUV
i need to make a CT under this specification
Shunt resistor RS and the current transformer are scaled such that a voltage signal of
no more than 1V peak-to-peak is present at the amplifier output when maximum
current flows through the primary of the current transformer and the amplifier is set to
minimum gain.
A prototype built for 230V and 10A operation showed better than 1% accuracy over
a dynamic range of 500:1. With careful PCB design and following the guidelines
given at the end of this document the accuracy can be further increased. The meter
is easily configured to fit any other voltage and current settings.
Remember our 10 amps that gave us .004 amp through the 68 ohms for a voltage of .272? Well let's amplify that .272 * 1.25 and we get 0.340 Volts RMS. To get the peak value we multiply that 0.340 * 1.414 = 0.48076 Volts Peak and the Peak to Peak is now = 0.4876 * 2 = 0.96152 Volts Peak to Peak. There are a few ways to arrive at this number as can be seen in the AVR sheet but you should get the idea
It's getting more clearer to me now. I have got a CT of 200:5 ratio. I think i can connect it with the load, but the problem is, i got one pcs, so what if i don't take the reading of neutral? My understanding is the T1 and T2 both same circuit, the mcu compare the current in both circuit and take the maximum value as result.
I did not understand where do u get 1.414 of 0.340 * 1.414 = 0.48076 and 2 of 0.4876 * 2 = 0.96152?
Another thing is our line is 230volt line, so i think that will change calculation for Rshunt for the CT of 200:5 as you did above?
My understanding is the T1 and T2 both same circuit, the mcu compare the current in both circuit and take the maximum value as result.
For sine waves:
To calculate the RMS value of a sine wave, multiply the peak value by 0.707. The peak value is, of course, one half the peak-to-peak value. To go the other way, reverse the order of operations. That is, if you're starting with an RMS value, divide by 0.707 and then multiply by two to get the p-p value. Another way to convert from RMS to p-p is to multiply the RMS value by two square roots of two: RMS x 2 x SQR(2).
Or more simply, to convert from RMS to peak to peak voltage:
(RMS x 1.414) x 2=P-P
For example:
120vac x 1.414= 170vac
169.68vac x 2 = 339.36vac P-P
This application note describes a single-phase power/energy meter with tamper logic. The design measures active power, voltage, and current in a single-phase distribution environment. It differs from ordinary single-phase meters in thatto measure active power in both live and neutral wires. This enables the meter to detect, signal, and continue to measure reliably even when subject to external attempts of tampering.it uses two current transducers
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