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This device uses the ammeter with full-scale deflection of 0. Also refer to Transistor Multivibrator Circuits.
All this allows to create very simple frequency meter circuit with several iic ranges:. The pulse frequency depends on the input frequency. C5 and trimming potentiometers R Adjust the trimming potentiometer R3 to move the needle of ammeter PA1 to the maximum value on the scale.
There are two different methods of connecting Rx and Cx.
Frequency meter with monostable multivibrator
The Figure 1 shows the circuit diagram of the frequency meter, the circuit based on the digital IC The load Capacitance CL is 50pF, including scope probe, wiring, and any stray capacitance. Frequency meter with monostable multivibrator Digital integrated circuits can be used in the design of an analogue frequency meter with a frequency range to several MHz.
The first chart works for either the 74L or 74L; however, the second chart only applies 71421 the 74L How to Read Logic Truth Tables: VD4 protects iv integrated circuit from overloading. 74211 IC is the monostable multivibrator that may generate a pulse of a different width from 35 ns and wider that depends on RC components. A Monostable Multivibrator is also called a One Shot.
or Timer as a One-Shot
The shown above provides a single Monostable Multivibrator function. 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 method for a Cx of less than pF [below] and a second connection [below that] for an external capacitor, Cx, of greater than pF.
Note the uses a 4k internal resistor, while the uses a 20k resistor. The two graphs below show the resultant pulse width for different values of resistors and capacitors. To use the internal timing resistor connect Rint to Vcc. The Diodes used in the circuit are 1N or equivalent.
Electronic Engineering Dictionary
The pulse 741121 produced by the monostable multivibrator depends on the values of capacitors C The ammeter PA1 indicates the voltage across the capacitor C1. You’ll need a source of stable frequency reference signal that can produces a set of frequencies Hz, 1 kHz, 10 kHz and kHz.
By the way, the ammeter PA1 can be replaced with a digital multimeter. Reference oscillator circuit diagram.
Frequency meter with 74121 monostable multivibrator
The number of frequency ranges can be increased by lc a rotary switch SA1 with more than four positions, and by adding some additional RC components.
The device can measure sinusoidal wave and square wave input signals. While the shown below provides a retriggerable Monostable Multivibrator function with 741211. Digital integrated circuits can be used in the design of an analogue frequency meter with a frequency range to several MHz. 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 pulse voltage is proportional to the input frequency, through the diode VD5 this voltage charges the capacitor C1.
Instead ofthe SN or DM can be used. All this allows to create ix simple frequency meter circuit with several frequency ranges: 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.
How to calibrate this frequency meter? Do the same operation for all ranges. 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.