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Weekly Report
Omar Nasr
As a group the decision for choosing a method to conduct this project has been
decided. The design using white noise has been eliminated due to hardware
complications that deal with generating white noise to stimulate the crystal. There are
other complications in using the white noise method as finding the components necessary
to function at a high frequency. Therefore the VCO method has been selected for its
simplicity in finding hardware IC’s that will be operating at lower frequencies.
Continuing from last weeks development of the design there has been a few additional
components added to the design. Figure 1 shows a general view of the design after adding
the additional components.
Figure 1
Voltage Controlled Oscillator (VCO)
Using the voltage controlled oscillator this will allow the user to control the input sine
wave into the crystal. The VCO used is an IC Max038 that generates sine waves. This
way we will be able to change the voltage over the crystal. This chip can generate
frequencies from the range of 0.1Hz to 20MHz, which is a very good range for the
frequencies that this crystal will be operating.
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Weekly Report
Omar Nasr
POA 1
This power operational amplifier has low output impedance, and a high gain factor that
will stabilize the frequency of the input signal going into the crystal. The max4493
operational amplifier will be used since it has a 1MHz gain bandwidth.
POA 2
This Op-amp will be the same as POA 1, used for the same reason to stabilize the signal
frequency.
HSC Comparator
The comparator here is used to compare input analog signals which will then output this
signal as a binary signal.
True Root Mean Square (TRMS)
These are true RMS to DC converters. This will convert the input signals into a DC
waveform which will be fed to the computer for data analysis. There are 2 TRMS in the
circuit because one will be the voltage coming out from the crystal and the other will be
the input current of crystal. TRM 1 has a voltage output that is proportional to the current
going into the crystal. Finding these values will allow us to obtain the admittance which
is equal to the current divided by the voltage.
Phase Detector
This device detects the phase difference between two into signals. Using the AD4044
phase detector we can find the phase difference between the input and output signal of
the crystal.
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Weekly Report
Omar Nasr
Low Band Pass Filter (LPF)
The LPF will filter out of band frequencies that can interfere with the signal we are
looking for. The LPF will also function as an ADC so that the output signal will be in DC
form.
By finding the admittance and the phase difference from the crystal we can then send the
data to the computer for data analysis and find the viscosity and visco-elasticity for the
fluid sample.
Week Accomplishments:
Parts have been ordered and still waiting for them to arrive. The following components
are ordered:
Max038 Voltage Controlled Oscillator
Max 7425 Low Band Pass filter, and Max 7491 Universal Band pass filter.
Max 4493 Operational Amplifier
Max 9025/27 Comparator, and Max 9015 Comparator.
Mx536A TRMs
Reference:
Robert Northrop
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