Download In this method cross correlation is used to find the impedance of the

Omar Nasr
Weekly Report
In this method cross correlation is used to find the impedance of the crystal,
reducing much of the complications thought of before, and also minimizing the error
percentage. Using white noise as an input signal will drown out interfering signals
coming from surrounding obstacles that can affect results. The white noise signal will be
stimulated by the computer using a software program, which will then be sent to a D/A
converter. The signal coming out from the D/A converter will stimulate the crystal to
oscillate via an Op-amp. Using the Op-amp here will be beneficial in allowing low output
impedance, and flat frequency response. The crystal’s output signal will then be fed into
an Op-amp of the same type as the input. The signal will then be converted back to digital
using an A/D converter, which will then be sent to the computer for data analysis. Using
this data the impedance can be measured and by finding the impedance components the
viscosity can ultimately be found.
In the process a TTL signal is also taken into consideration as it will keep the system
coordinated together, which will be used to mark the beginning of each stimulus while
collecting data.
To apply white noise input using a stimulator the design would require a ‘pseudo random
binary noise source’ which would be complex in design.
Figure 1 shows a general view of the design components.
Figure 1
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Omar Nasr
Components to be used:
Analog Devices Catalog
AD 8033 Op-Amp is a voltage feedback amplifier which has a small signal bandwith of
80 MHz
AD 7656 Converter operates with an input bandwidth of 50 KHz.
AD 7273 Converter operates with an input bandwidth of 1 MHz.
AD 5660 16-Bit nanoDAC converter.
Using another approach a voltage controlled oscillator (VCO) generates an AC
control voltage signal which is sent to the crystal by an Op-amp having it oscillate at a
defined input. Using the Op-amp here will also be beneficial in allowing low output
impedance, and flat frequency response. The output from the crystal will then be sent to
another Op-amp of the same type as the input Op-amp. The output from this Op-amp will
then be fed into a comparator which will identify between the high and low voltages. This
will also be performed for the input signal going into the crystal. From this point the data
is sent to a phase detector which output the phase difference signal. The output from the
phase detector will then be sent to the computer for analysis. The impedance components
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Omar Nasr
of electrical resonant resistance and resonant frequency shift can then be found to solve
for viscosity, and visco-elasticity. The resonant resistance and the resonant frequency are
proportional to the viscosity of the fluid, and thus the viscosity can be determined.
Figure 2 shows a general overview of the design layout.
Figure 2
Components that will be used:
Max 08 Voltage Controlled Oscillator
LUCDA4044 Phase Frequency Detector
LM339 Comparator
Communicator to send information to computer
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