Frequency meter circuit composed of CD4046

The frequency meter uses the hands to indicate the level of the measured frequency. R1 is made up of a 47k fixed resistor in series with a 51k potentiometer. R4, R5 and C4 form a low-pass filter. R3 is connected in series with the meter M as a source follower load. R3 is also used to adjust the full-scale current of the meter. There is a large capacitance of 100LF on the meter head to eliminate the jitter of the hands at low frequencies. The measurement range of the frequency meter is 20Hz ~ 1kHz. When calibrating with a standard signal generator and a standard frequency meter, the 51k potentiometer needs to be adjusted, which has good linearity. The frequency meter circuit composed of CD4046: