Saturday, 17 March 2012

AF Wave analyzer principle and Working



AF Wave analyzer principle and Working :

The wave analyzer consists of a very narrow pass-band filter section which can
Be tuned to a particular frequency within the audible frequency range(20Hz to 20 KHz)).





The block diagram of a wave analyzer is as shown in fig
The complex wave to be analyzed is passed through an adjustable attenuator which
serves as a range multiplier and permits a large range of signal amplitudes to be analyzed without
loading the amplifier.




The output of the attenuator is then fed to a selective amplifier, which amplifies
the selected frequency. The driver amplifier applies the attenuated input signal to a high-Q active filter. This high-Q filter is a low pass filter which allows the frequency which is selected to pass and
reject all others.
 The magnitude of this selected frequency is indicated by the meter and the filter section identifies the
frequency of the component. The filter circuit consists of a cascaded RC resonant
circuit and amplifiers. For selecting the frequency range, the capacitors generally used are of the closed tolerance polystyrene type and the resistances used are precision potentiometers. The capacitors are used for range changing and the potentiometer is used to change the frequency within the selected pass-band, Hence this wave analyzer is also called a Frequency selective voltmeter. The entire AF range is covered in decade steps by switching capacitors in the RC section
.
The selected signal output from the final amplifier stage is applied to the meter
circuit and to an unturned buffer amplifier. The main function of the buffer amplifier is to drive
output devices, such as recorders or electronics counters.
The meter has several voltage ranges as well as decibel scales marked on it. It is
driven by an average reading rectifier type detector. The wave analyzer must have extremely
low input distortion, undetectable by the analyzer itself. The band width of the instrument is
very narrow typically about 1% of the selective band given by the following response
characteristics shows in fig.


the applications of wave Analyzer........
1. Electrical measurements
2. Sound measurements
3. Vibration measurements.
In industries there are heavy machineries which produce a lot of sound and vibrations, it is very
important to determine the amount of sound and vibrations because if it exceeds the permissible

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