The variable diameter tachometer will read in IPM (inches per minute) on a 4-digit 5/8" LED Display. The diameter settings made on two (2) potentiometers, one having Tens scale and the other having Units scale for diameters of 0" to 260" in 1" increments. A selector switch is provided for IPM or RPM checking. This device comes in a metal case with a shielded remote cable and has handles and holes for hanging purposes. The actual running speed sensed by a precision generator.