Schematic Rise

This proposed analogue frequency meter circuit may be used as a pulse counter, tachometer, or if preceded by a Schmitt trigger, an analogue frequency meter.
Output linearity better than 2% can be obtained with duty cycles of less than 30%. The meter is selected so that it reads full scale when the duty cycle of the UL914 is 30%. The choice of C1 and the meter sensitivity determines the range of measurement. Potentiometer RV1 is used to calibrate the meter to full scale deflection, and resistor R2 counteracts the slight zero offset of the saturated lC. Diode D1 protects the meter.