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A quartz crystal oscillator circuit that can generates kHz signal with a 3-stage decade counter can be used as a reference frequency source see the Figure 2. The device can measure sinusoidal wave and square wave input signals. C5 and trimming potentiometers R How to calibrate this frequency meter? The Figure 1 shows the circuit diagram of the frequency meter, the circuit based on the digital IC The shown above provides a single Monostable Multivibrator function.
The load Capacitance CL is 50pF, including scope probe, wiring, and any stray capacitance. Adjust the trimming potentiometer R3 to move the needle of ammeter PA1 to the maximum value on the scale. Digital integrated circuits can be used in the design of an analogue frequency meter with a frequency range to several MHz. Turn the rotary switch S1 of the frequency meter to the range of Hz and connect the device to the reference signal source of Hz.
The first chart works for either the 74L or 74L; however, the second chart only applies to the 74L There are two different methods of connecting Rx and Cx. The circuit could be used for any TTL family, such as LS, or H, but the load capacitor might need to be changed to reflect that. Do the same operation for all ranges.
The first method for a Cx of less than pF [below] and a second connection [below that] for an external capacitor, Cx, of greater than pF.
All this allows to create very simple frequency meter circuit with several frequency ranges:. While the shown below provides a retriggerable Monostable Multivibrator function with clear.
or Timer as a One-Shot
Frequency meter if monostable multivibrator Digital integrated circuits can be used in the design of an analogue frequency meter with a frequency range to several MHz. Note the uses a 4k internal resistor, while the uses a 20k resistor. How to Read Logic Truth Tables: This device uses the ammeter with full-scale deflection of 0.
The Diodes used in the circuit are 1N or equivalent.
Frequency meter with 74121 monostable multivibrator
The pin out diagram works any any style 74xx or 74xx DIP chip, but the timing graphs are only valid for the TTL families indicated. The number of frequency ranges can be increased by using a rotary switch SA1 with more than four positions, and by adding some additional RC components.
The pulse voltage is proportional to the input frequency, through the diode VD5 this voltage charges the capacitor C1. To use the internal timing resistor connect Rint to Vcc. Reference oscillator circuit diagram. I two graphs below show the resultant pulse width for different values of resistors and capacitors.
Instead ofthe SN or DM can be used. The ammeter PA1 indicates the voltage across the capacitor C1. A Uc Multivibrator is also called a One Shot.
This IC is the monostable multivibrator that may generate a pulse of a different width from 35 ns and wider that depends on RC components.
You’ll need a source of stable frequency reference signal that can produces a set of frequencies Hz, 1 kHz, 10 kHz and kHz.
All this allows to create very simple frequency meter circuit with several frequency ranges: The pulse width produced by the monostable multivibrator depends on the values of capacitors C VD4 protects the integrated circuit from overloading. Also refer to Transistor Multivibrator Circuits. By the way, the ammeter PA1 can be replaced with a digital multimeter. The pulse frequency depends on the input frequency.