Coupling power transformer to ADC

[ashugtiwari]

Hello All,
In one of my power circuit powered through a step down power transformer converting 230V ac rms to +-5Vp-p for powering circuit ahead. I want to get the instantaneous value of AC supply through ADC sampling at higher rate to find different values. Is the circuit shown can work to interface transformer output to ADC input or some different circuit should be used?

As far as capacitor goes, I added it to decouple DC to transformer outputs. How to get capacitor value to have negligible phase delay?

Thanks
Ashutosh

 

[smijesh]

Power transformer will do the voltage isolation, Then voltage level should be considered. ADC voltage level seems to be 3.3V , So you should be attenuate ac voltage(10VRMS) to 3 voltage peak to peak , then no clipping happen. For coupling you can use 100nF to 10uF capacitor it will also attenuate the AC signal.

In the real world you would need to design op-amps as buffers before ADC

 

[KlausST]

Hi,

It can´t work with only one connection at the secondary transformer side.
and as smijesh noted you need a third resistor for input signal attenuation.


Klaus