High-precision delay timer (CD4016AE, LM307N)

As shown in the figure, this is a high-precision delay timing circuit. In the figure, Rt and Ct are timing elements, and the timing time is T=RtCt(s). In order to adjust the timing time, it can be achieved by changing Rt and Ct, but doing so will make the stability worse, so it is generally achieved by adjusting the comparison level of the comparator, that is, adjusting RV1 in the figure. This circuit is to improve the timing accuracy. It requires the use of stable comparators, capacitors, resistors, and mode switches with no offset voltage, low on-resistance, and high off-resistance. Therefore, the comparator generally uses an operational amplifier, such as LM307N; Ct uses polystyrene or polycarbonate capacitors; Rt uses metal film resistors; analog switches are best to use CMOS devices, such as CD4016AE in this circuit.