Frequency Counter/Tachometer with High Precision

For convenient reading, the display of this tachometer circuit show inthe reading in hertz directly.  The conversion time will be equal to the gating time, which is 0.1 second with pin 11 of the ICM7027A connected to Vdd, make the display show tens of hertz at the least significant digit. An ICM7207 can be used with a 6.5536 MHz crystal for shorter gating times, giving a 0.001 second gating with pin 11 connected to Vdd, and 0.1 second gating with pin 11 open.