Hi there,I have a rpm sensor that I want to interface to an Arduino. I am not sure what I need to search for?It is on an old Starter/Alternator test bench and is used to drive an analogue gauge. It has a shaft driven straight off the front of an Alternator/Starter Motor.I have run up the sensor and I get out of the 2 wire an AC voltage which varies depending on speed. I got out 500mV AC just running it up with a drill at full speed. I want to interface it to the Arduino but I am not sure what to do with AC voltage. I am using an MCP3208 for 2 other circuit as the resolution wasn't enough with the 10 bit onboard ADC.