Electronic measuring instruments
Signal generator is electronic equipment that provides standard testing signals like sine wave, square wave , triangle wave, etc. It is also called an oscillator because it produces periodic signals.
The signal generator, which produces the periodic signal having a frequency of audio frequency (AF) is called AF signal generator . the audio frequency range is 20 Hz to 20 kHz.
Sine and Square Wave AF Generator
The AF signal generator, which generates sine wave or square wave in the range of audio frequencies on the requirement is called Sine and square wave generator AF. Its functional diagram is illustrated in the figure below.
The diagram above consists mainly of two paths . These are the upper path and the lower path. The upper path is used to produce a wavesinusoidal AF and the lower path is used to produce a square wave AF.
The Wien Bridge Oscillator will produce a sine wave in the range of audio frequencies. According to the requirement, we can connect the output of the Wien bridge oscillator to the upper path or the lower path by a switch.
The upper path consists of blocks like the sinusoidal amplifier and attenuator. If the switch is used to connect the oscillator output of the Wien bridge to the upper path, it will produce a desired AF sine wave at the output of the upper path.
The lower path consists of the following blocks: square waveform, square wave amplifier and attenuator. Square wave shaper converts sine wave to square wave. If the switch is used to connect the oscillator output of the Wien bridge to the lower path, then it will produce a car wave.AF road desired at the exit of the lower path. In this way, the block diagram we have considered can be used to produce either an AF sine wave or AF square wave based on the requirement.
The function generator is a signal generator, which generates three or more periodic waves. Consider the following block diagram of a function generator, which will produce periodic waves such as triangle wave, square wave, and sine wave.
There are two current sources , namely upper current source and lower current source in the diagram above These two current sources are regulated by the frequency controlled voltage.
The integrator shown in the diagram below above, obtains constant current alternately from the top and bottom current sources for an equal time repeatedlytee. So the integrator will produce two kinds of output for the same time repeatedly -
The output voltage of an integrator increases linearly with respect to time for the period during which the integrator receives current from the upper current source.
The output voltage of an integrator decreases linearly with respect to time for the period during which the integrator obtains the current from 'a weaker current source.
In this way, the integrator shown in the diagram above will produce a triangle wave .
Square wave and sine wave
The output of integrator, i.e. triangle wave is applied as input to two other blocks as shown in the diagram above in order to get the square wave and the sine wave respectively. Let's discuss these two one by one.
The triangle wave has a positive slope and a negative slope alternately for an equal duration repeatedly. Thus, the voltage comparator multi-vibrator shown in the diagram above will produce the following two types of output for an equal duration repeatedly.
A type of co voltage (higher) at the output of the multi-vibrator voltage comparator for the period during which the multi-vibrator voltage comparator obtains the positive slope of the triangle wave.
Another type of constant (lower) voltage at the output of the multi-vibrator voltage comparator for the period during which the multi-voltage comparator -vibrator obtains the negative slope of the triangle wave.
The voltage comparator multi-vibrator shown in the diagram above will produce a square wave . If the amplitude of the square wave producese at the output of the multi-vibrator voltage comparator is not sufficient, it can be amplified to the required value by using a square wave amplifier.
The sine wave shaping circuit will produce sine wave output from the sine wave 'triangular entrance. Basically, this circuit consists of a network of diode resistors. If the amplitude of the sine wave produced at the output of the sine wave shaping circuit is insufficient, it can be amplified to the required value by using a sine wave amplifier.