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The resultant signal should be an 800 mV sine wave with minimal offset.

Using the inverting gain circuit shown in Figure 8, amplify the output of the differential amplifier circuitby an additional factor of ten. This can be done with another op-amp and a 10 k ohm resistor and a 30 k ohm resistor. Theresultant output signal should have a mean of zero and amplitude of ~2.4 V. Adjust the potentiometer to remove any offset.

Differential Amplifier Circuit

Part 7: low-pass filtering

A low pass filter can be used to attenuate high-frequency noise in an analog signal and to minimize the portion of the signal that will be aliased. Later in this lab, youwill see a demonstration of the damaging effects of aliasing.

First-Order Low-Pass Filter

7.1 build an active low-pass filter

  • Build the first-order filter shown in Figure 9 with R1 = R2 = 10 k ohm and C2 = 0.1 micro F. First order filters are so-called becausetheir dynamics are modeled by first-order differential equations.
  • Connect the output of the circuit to Channel 1 on your DAQ system.
  • The filter’s time constant is equal to R2C2. Calculate values for the cut-off frequency and the time constant.

7.3 modifying existing vi to measure magnitude ratio

By measuring the magnitude of the input and output of a filter, you can determine the how much the filterattenuates the signal.

Completed Block Diagram
  • Delete the Amplitude and Frequency constants from the Block Diagram.
  • Hold Ctrl as you drag the Tone Measurements icon to make a copy.
  • Place a Split Signals icon to the left of the Tone icons.
  • Place a Divide function to the right of the Tone icons.
  • Create a numeric indicator at the x/y output terminal of the Divide function.
  • Rename the numeric indicator Magnitude Ratio. (The Magnitude Ratio represents the output amplitude divided by the inputamplitude.)
  • Wire the Block Diagram as shown in Figure 10.
  • Save the VI.

7.2 testing a filter

We expect that the filter will allow frequencies below the cut-off frequency to "pass", and willattenuate signals at higher frequencies. The Magnitude Ratio will be recorded as the output magnitude divided by the inputmagnitude.

  • Connect the signal going into your filter to Channel 0 of module 1 of the SCXI.
  • Connect the signal coming out of your filter to Channel 1 of module 1 of the SCXI.
  • Input a 1 V sine wave with zero offset into the low-pass filter circuit.
  • Starting with a frequency of about 10 Hz, slowly increase the frequency of the input signal. What happens to the outputsignal?
  • Increase frequencies to 2 kHz.
  • Using the table below, determine the magnitude ratio at several frequencies.

Table 1: Magnitude Ratio Data for First-Order Low-Pass Filter (Active)

frequency (Hz) Input magnitude (V) Output magnitude (V) Magnitude ratio
10 1V
18 1V
32 1V
58 1V
110 1V
190 1V
340 1V
620 1V
1100 1V
2000 1V
  • Using Excel, plot the following two sets of data on a single log-log chart.
    • Calculated magnitude ratio vs. frequency.
    • Measured magnitude ratio vs. frequency

Do the magnitude ratio and phase difference between the input and output behave as you would expect?

Questions & Answers

anyone know any internet site where one can find nanotechnology papers?
Damian Reply
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
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s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
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are you nano engineer ?
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That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
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Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
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for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
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what is biological synthesis of nanoparticles
Sanket Reply
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Source:  OpenStax, Introduction to mechanical measurements. OpenStax CNX. Oct 18, 2006 Download for free at http://cnx.org/content/col10385/1.1
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