Dual range tachometer

摘要

A tachometer has a display responsive to an rpm signal for producing an observable indication of an rpm value. A circuit responsive to an engine input develops a standard rpm signal representative of instantaneous engine rpm, and a differential Power Band amplifier circuit amplifies the difference between the standard rpm signal and an adjustable "offset" rpm signal by predetermined gain to produce an amplified differential rpm signal. A switching circuit selects the standard rpm signal or the amplified differential rpm Power Band signal for driving the display. A peak or valley rpm signal may also be developed and selected for display either in a standard mode or a differentially amplified Power Band mode.