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How to Make an Analog Frequency Meter

Frequency meters measure the frequency from signal generators. They do this by counting the number of pulses, or oscillations, so are also called frequency counters. Two of their roles are to test and fix circuits or electronic devices. Frequency meters may be analog or digital. To make an analog frequency meter, build a circuit that can perform a voltage to frequency conversion. An example is a circuit made with a 555 timer chip and a meter. A resistor and capacitor combination sets the maximum frequency range.

Things You'll Need

555 timer chip
3 4.7k-ohm resistors
10k-ohm resistor
10k-ohm potentiometer
0.01uF capacitor
0.1uF capacitor
Signal generator
0-1 mA meter
9V battery
Battery holder
Breadboard
Jumper wires

Instructions

- 1
  Select the maximum frequency (f) for the circuit. The circuit is based on a monostable multivibrator, which means it outputs a stable pulse. The equation to select the frequency is f = R * C, where R is a resistor, and C is a capacitor.
- 2
  Calculate the frequency using the values of R = R3 = 10k, and C = C2 = 0.01. The maximum frequency is 10k *0 .01 = 1kHz, or kilohertz.
- 3
  Connect the 555 chip to the breadboard. Its notch must face left, so its pins may be counted counterclockwise. Each of the pins must be in a different column.
- 4
  Connect pins 6 and 7 by placing a small jumper wire between them. Use a jumper wire to connect pin 4 to the breadboard voltage source row or column, then do the same for pin 8.
- 5
  Attach the 0.1 capacitor between pin 5 and a breadboard row or column selected as ground. Attach pin 1 to ground.
- 6
  Connect one end of the first 4.7k resistor to the voltage source, and its other end to pin 2. Connect one end of the second 4.7k resistor to pin 2 as well, but connect its other end to ground.
- 7
  Place the 10k resistor between pin 6 and the voltage source. Put one end of the 0.01 capacitor at pin 7, and put its other end at ground.
- 8
  Attach one end of the remaining 4.7k resistor to pin 3, and attach its other end to the voltage source. Attach the middle, or wiper part of the potentiometer, to pin 3. Insert one of its other ends into an unoccupied column on the breadboard. Add one end of the 100 resistor to this same column, and connect the resistor̵7;s other end to the positive lead of the meter. Attach the meter̵7;s negative lead to ground.
- 9
  Adjust the signal generator so it outputs a 1kHz sine or square wave. Connect its positive lead to the chip̵7;s pin 2, and attach its negative lead to ground. Add the battery holder to the circuit, attach the 9V battery to it, then turn the signal generator on.
- 10
  Calibrate the meter by turning the potentiometer knob. For example; adjust it so a reading of 1.0 means 1kHz, while 0.5 means 500Hz. Recalibrate the meter if the values for C2 and R3 are changed.

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