Encoders can detect speed when output pulses are counted in a specified time span. The number of pulses in one revolution must also be known. In the equation here, “S” represents speed, “C” represents the number of pulses counted, “PPR” the resolution of the encoder, and “t” represents the time interval in seconds during which the pulses were counted. The second equation shows that if 60 pulses are counted in a time interval of 10 seconds using a 250 CPR encoder, the shaft speed is 1.44 RPM.