Looking for a low-cost voltage and current acquisition solution

linkai

Looking for a low-cost voltage and current acquisition solution [Copy link]

Who can use a single-chip microcomputer to collect single-phase and three-phase voltage and current data?

maychang

If isolation is not required, the voltage can be collected by using resistors for voltage division, and the current is best collected by using a current transformer.

If isolation is necessary, a small voltage transformer (actually a current transformer with a large primary series resistor) is used to collect the voltage, and a current transformer is still used to collect the current.

Of course, to collect three-phase voltage and current, three voltage transformers and three current transformers should be used.

Theoretically, because the sum of the three-phase voltage and current phases is zero, only the two-phase voltage and current need to be collected. However, this is only possible when the three phases are symmetrical. When the three phases are asymmetrical, three voltage transformers and three current transformers are still required.

linkai

AD conversion generally involves DC voltage acquisition. How is AC voltage converted into DC? Is it converted into DC using a bridge and then rectified with a capacitor and then divided by a resistor, or is it divided by a resistor first and then converted into DC? I don't know how to acquire the AC voltage signal.

chunyang

What is "low cost" can only be determined by considering the specific application. The original poster should first state the specific application requirements.

maychang

linkai posted on 2019-9-9 13:14 AD conversion is generally DC voltage acquisition. How to convert AC voltage into DC is to use a bridge to convert it into DC, add capacitors to rectify it, and then use resistors to divide the voltage. ...

It is not allowed to connect the current transformer directly to the secondary side of the transformer using a rectifier bridge, as this will cause the current transformer core to saturate, the waveform to be distorted, and the error to be very large.

A bias can be added so that the signals input to the A/D are all in the same direction, or precision rectification can be used to take the absolute value of the AC signal before sending it to the A/D.

linkai

There is a feasible solution now, but there is no complete solution to implement it considering the cost improvement.