555 direct reading frequency meter schematic
Posted on Dec 11, 2010 8239
Direct reading frequency meter by the amplifier, and trigger one-shot circuit and table top components. It can be directly detected in the read head of the table 1mA signal, th
e maximum signal frequency up to 20kHz, sensitivity is not less than 100mV. IC1, IC2 using LM741 operational amplifier is used as a first amplifying stage, the second stage is a Schmitt trigger, the input signal is shaped so that the frequency of IC2 output signal frequency of the input signal is the same. Independent of the input signal amplitude. 555 and R12 ~ R15, C5 etc. monostable trigger circuit, monostable duration of temporary stability in accordance with the level of the input signal frequency, choose a different time constants, or file, 555 output high duration proportional to the frequency of the input signal, thereby changing table pointer deflection angle. DW regulator use as a chopper, so added to the header of the same pulse amplitude. 555 can be varied to adjust RP1 internal comparator reference voltage value, that is the time to change the monostable continued to the present frequency meter calibration.