a) getting the signal voltage down to a 5V or 3,3 V level.
A resistor divider would work
b) measuring the frequency with an arduino.
Count the number of input voltage transitions in a period of time using millis() for timing
a) getting the signal voltage down to a 5V or 3,3 V level.
A resistor divider would work
b) measuring the frequency with an arduino.
Count the number of input voltage transitions in a period of time using millis() for timing