Sine Wave Tracking

Thread Starter


Joined Oct 8, 2012
I need to track the sine wave of a 240vac line. I want to isolate the ADC completely from the 240vac. I visualize a bridge and divider into an specialized optical isolator with data and power on the other side to a remote micro and ADC. Does anyone have any recommendations for parts? I don’t want to reinvent the wheel, are there already devices available? Thanks.


Joined Jan 15, 2015
You can try a Google of ZMPT101B (AC Output Voltage Sensor Active Single Phase Voltage Transformer Board Module for Arduino Mega ZMPT101B 2mA). While they mention Arduino the module is useable with any uC having ADC capabilities.



Joined Jun 5, 2013
What do you mean by track? Do you need to sample the voltage throughout the cycle, or just sync to the frequency? If the latter, a zero cross detector is what you need.



Joined Aug 7, 2020
If you need the phase to be correct use one of these:
not one of these:

The split bobbin transformers have much lower L(mag) and much higher L(leak).
L(mag) is 12.6H for the split bobbin and 1600H for the toroid.
L(leak) is about 1H for both of them.
The low value of L(mag) gives a phase advance due to a highpass LR filter being formed.

If you are monitoring 3-phase for a missing neutral, you'll need a transformer with a 400V primary. A standard 230V transformer will saturate and burn out the primary if that happens.