555 Pocket digital frequency meter schematic
Circuit using an ordinary digital quartz electronic watch, the lower its crystal welding, as shown by the connected circuit constitutes a digital frequency meter. The test sign
al is applied to E, F side by R6, D3, D4, etc. limiter, and adjust RP1, control the intensity of the input signal. When measuring, click K5, the IC2 monostable delay circuit is set, four analog switch IC3 (CD4066) of CK2, CK3 closed, CK1 off, form the core of memory circuit is cut off, the signal being measured by CK2, R5, C4 is added to form the core of the D point, form the core division, counting circuit starts operating. To be a preset time, IC2 of 3 feet referred to the low level, CK2, CK3 off, CK1 is closed, the signal to be measured into the memory state. When reading, just click K4, the liquid crystal display panel will show the frequency of the signal to be measured. The timing switch K6 is divided into two tranches of 33 seconds and 328 seconds. When debugging, adjust RP3 at the second speed, timing of 328 seconds; adjust RP2 at the first speed for 33 seconds. A positive figure point of access electronic watch, B point of access form the core of the upper end of the function keys, C point of access form the core negative reed, D point of access to any foot pads quartz crystal. The reading on the LCD screen when a file, the value is multiplied by the frequency 1000Hz, the value is multiplied by 2 files 100Hz.