I am using a pic12f675 to measure the duration of a prox switch to determine rpm. The signal is a sine wave that increases in frequency and voltage with rpm. I have been running this signal right into an input pin and working just fine for a long time. Sometimes though I need to measure a lower rpm and because the voltage drops below the detectable voltage of the pic, it doesnt see the signal. What is my simplest way of showing a high signal over 1.5 volts and low signal under 1.5 volts? Noise hasnt been a problem with the higher voltages but could arise at the lower voltages?

Thanks all!

Jason