Microchip DSPIC blockset ADC reading issues

Hi I am using the Version 3.37 of microchip blockset and was trying to simultaneously read two channels (AN0 and AN1 ) and take its ratio. If I read DC with equal magnitude, the ratio read is 1 , but when I connected a low frequency AC signals, the ratio fluctuates between 0 and 1. Why and where from zero appears is not clear. Help will be greatly appreciated.

The custom C code is given below

#include<stdio.h>

void uart(unsigned int a , unsigned int b) { if(b/a==0) { printf("ratio is zero\n"); } }