# Ac voltage measurement

Hi!

I got a simple problem. My objective is to measure voltage and power factor of a 16V AC through a differential ADC (ADS1115) that measures voltage difference between 2 channels. I only managed to measure current accurately through a CT.

In the positive cycle of the the circuit shown, the voltage across the 1k resistor is 1.45Vp which is measurable. In the negative cycle, the voltage across the resistor will be -14.54V which will burn the ADC.

Hence, how do I modify this circuit to achieve a safe voltage measurement? I will need to detect the waveform at point 0V in order to compare it to the current then measure power factor. I thought of connecting A2 to the ground of the DC supply instead of the nuetral, but I was not sure if that's the right approach.

Sorry i'm a beginner. Any input/ advice will be highly appreciated.

• Do you need to digitize the AC waveform or are you just interested in measuring the peak-to-peak voltage? – kjgregory Nov 9 '17 at 15:57
• Is your ADC ground the same as the "DC Ground" in your schematic? – The Photon Nov 9 '17 at 17:32
• @kjgregory, Just interested in measuring the peak to peak voltage as well as the 0 crossing really for power factor. – Moha Sawyer Nov 10 '17 at 2:34
• @ThePhoton, Yes indeed it is. The bridge rectifier is also supplying the ADC. – Moha Sawyer Nov 10 '17 at 2:36