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N. Yadav and R. Dhar
both these analyzers. Amplitude and phase can be accurately measured by this kind
of analyzers.
2.2 Time Domain Techniques
Interfacial impedance can be deduced from the external perturbation and the corresponding output in time domain. Any time domain stimulus can be used to find
impedance but the response has to be recorded for a very long time so that the
transforms are completed over the chosen frequency range. Time domain can be
converted into frequency domain by myriad linear integral transforms such as
Laplace and Fourier transforms. Pound and Mcdonald [33] have evaluated several
time to frequency transformation methods which includes fast Fourier transform
(FFT), Laplace transform and a mathematical operation similar to FRA. Perturbation and response are recorded in digital format in time domain before processing
of signal by software. The accuracy of the transformations is critically dependent on
the acquisition of data of desired frequency and length irrespective of the mode of
processing.
2.2.1 Analog to Digital Conversion
Analog signal is converted into digital signal and finally into binary form in analog
devices which are equipped with digital recording and processing. The magnitude
of the converted binary form is proportional to the signal which is sampled. Two
operations viz. sampling and quantization are involved in the process of conversion.
The former freezes the analog signal in time to get a discrete value. In the later
operation, this value is changed into binary form with the cycle being repeated.
Numerous techniques of quantization are available. Selection of analog to digital (AD) converter is based on accuracy, precision, cost, power requirements and interfacing
ease. There are varieties of (A-D) converters such as successive approximation,
integrating, tracking, multi comparator, voltage frequency converter. All the above
mentioned methods have certain advantages as well as disadvantages. Successive
approximation method gives high speed and rates of conversion can be in the MHz
region but it has limited precision and accuracy as well as is prone to noise. Integrating
method gives more immunity to noise and has great precision.
2.2.2 Computer Interfacing
Interfaces operating at high level having a driver program are of paramount importance to experimentalist in implementing ac techniques. Commonly used high
level interfacing system is the general purpose interface bus (GPIB), also called
N. Yadav and R. Dhar
both these analyzers. Amplitude and phase can be accurately measured by this kind
of analyzers.
2.2 Time Domain Techniques
Interfacial impedance can be deduced from the external perturbation and the corresponding output in time domain. Any time domain stimulus can be used to find
impedance but the response has to be recorded for a very long time so that the
transforms are completed over the chosen frequency range. Time domain can be
converted into frequency domain by myriad linear integral transforms such as
Laplace and Fourier transforms. Pound and Mcdonald [33] have evaluated several
time to frequency transformation methods which includes fast Fourier transform
(FFT), Laplace transform and a mathematical operation similar to FRA. Perturbation and response are recorded in digital format in time domain before processing
of signal by software. The accuracy of the transformations is critically dependent on
the acquisition of data of desired frequency and length irrespective of the mode of
processing.
2.2.1 Analog to Digital Conversion
Analog signal is converted into digital signal and finally into binary form in analog
devices which are equipped with digital recording and processing. The magnitude
of the converted binary form is proportional to the signal which is sampled. Two
operations viz. sampling and quantization are involved in the process of conversion.
The former freezes the analog signal in time to get a discrete value. In the later
operation, this value is changed into binary form with the cycle being repeated.
Numerous techniques of quantization are available. Selection of analog to digital (AD) converter is based on accuracy, precision, cost, power requirements and interfacing
ease. There are varieties of (A-D) converters such as successive approximation,
integrating, tracking, multi comparator, voltage frequency converter. All the above
mentioned methods have certain advantages as well as disadvantages. Successive
approximation method gives high speed and rates of conversion can be in the MHz
region but it has limited precision and accuracy as well as is prone to noise. Integrating
method gives more immunity to noise and has great precision.
2.2.2 Computer Interfacing
Interfaces operating at high level having a driver program are of paramount importance to experimentalist in implementing ac techniques. Commonly used high
level interfacing system is the general purpose interface bus (GPIB), also called