Design and Development of a Low Cost Function Generator cum

Abstract

This- paper presents the design and development offunction generator/frequency counter for generating sine wave, square wave, and triangular wave. It might be used to measure the input frequencies from 0 to 20kHz of amplitude 5volts. It has two ranges for frequency selection XI & XI 0 and four ranges for X2, X20, X200 & X2K frequency measurement.

Keywords: Function Generator, Frequency Counter, Sinusoidal, Triangular and Square Waves.

Introduction

Function Generator Frequency Counter are very convenient for indoors use and it is widely used in research laboratory or any educational institute. In order to obtain all the waves viz. sinusoidal, triangular and square waves, the waveform generator chip 8038 has been employed. In fact, the 8038 is a monolithic IC capable of generating sinusoidal, triangular and square waves with high accuracy . The output waveforms require suitable amplification, as they would not be in same amplitude level. To maintain similar amplitude levels, voltage amplifiers have been used. It has facilities to change the frequency range from 20Hz to 20KHz and the duty cycle of frequency with a switch. It has an easy handling ON/OFF switch and a BNC socket to connect the output of the frequency counter to other device. It has an analogue display unit to read the frequency of the device. The function generator/ frequency counter comprises of the following units:

i)          Waveform selector circuit

ii)         Waveform generating circuit

iii)         Frequency selector circuit

iv)        Pulse shaping amplifier circuit

v)         Range selector circuit

vi)        Meter driver and display circuit.

The specifications of the designed function generator /frequency counter are given in Table 1.

Table 1: Specifications of the Function Generator / Frequency
Counter

Feature Specification
Case	Size	250X95XI30mm including handle
	Weight	1.3kg
	Material	Plastic
Frequency range		1) X1
		ii) X10
Waveform selection		i) Square wave.
		ii) Triangular wave
		iii) Sine wave
Range selection		i) X2
		ii) X20
		iii) X200
		iv) X2000
Power supply		+ 5Volts dc
Indication		1001tA fsd, linear •anel meter

Principle of Operation

The wave generator IC produces sine, square & triangular waveforms. This wave is feed to a monostable IC through a switch, which shapes the pulse. The shaped pulse supplies current for read out to the meter. The frequency range can be selected with a range selector switch from 20Hz to 2KHz.

  

Range Selector circuit:

The range selector circuit is consisting of R₉- R₁₂, VR_3­ -VR₆,C₄, D₂ and switch SW₃. When the switch SW₃- is in X₂ position, the +5volt supply is connected in series to the resistor R₉ and VR₃ to the pin 2 of IC₂ and capacitor C₄ is connected to the ground. When the switch SW₃ is in X20 position, the +5volt supply is connected in series to the resistor R_1O and VR₄ to the pin 2 of IC₂ and capacitor C₄ is connected to the ground. When the switch SW₃ is in X200 position, the +5volt supply is connected in series to the resistor R₁₁ and VR₅ to the pin 2 of IC₂ and capacitor C₄ is connected to the ground. When the switch SW₃ is in X200 position, the +5volt supply is connected in series to the resistor R₁₂ and VR₆ to the pin 2 of IC₂ and capacitor C₄ is connected to the ground.

Meter Driver and Display Circuit: The meter and driver circuit is consisting of R₁₃, R₁₄, R₁₅, VR₇ and IC₃. The output of IC₂ is connected to pin 3 of IC₃ via a resistor R₇ and output of IC₃ from pin 6 is connected to the positive of meter M via a R₁₅ and VR₇. The variable resistor VR₇ is used to calibrate the rate meter in full-scale deflection. The amount of deflection is proportional to the average current flows through the meter. The larger the value of the capacitor, the longer time it takes to charge and discharge.

Conclusion

The function generator cum frequency counter was put under a series of tests and its performance was very satisfactory. As this instrument fulfills the specification to calibrate the dose rate equipment, it can be use for calibration of Dose Rate Meter, Area Radiation Monitor, and Hand & Shoe Radiation Monitor etc. The overall cost of our designed function generator/ frequency counter is relatively low compared to the imported ones.

Design and Development of Area Radiation Monitor

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