automotive tachometer is used to measure the revolutions per minute
(rpm) of both two and four stroke engines, and distributorless ignition
Automotive tachometers use inductive pickup to measure the rpm rate,
and the LCD display provides at-a-glance information.
Automotive Tachometers are designed to clip over one of the spark
plug wires, then the number of cylinders is input into the machine
and it uses this information, coupled with the rate of electrical
pulses for calculating the rpm.