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Quiz 3

Quiz 3. ME368 Spring 2011. Open: book, notes, calculator. Closed: laptop, wireless device, neighbor. Data from National Instruments specification sheets can be summarized as follows:. Calculate the digital resolution, Q [V], for the 9211 module.

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Quiz 3

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  1. Quiz 3 ME368 Spring 2011 Open: book, notes, calculator Closed: laptop, wireless device, neighbor Data from National Instruments specification sheets can be summarized as follows: Calculate the digital resolution, Q [V], for the 9211 module. How many 9215-module data points must be averaged to bring Sx,9215,averaged down to Sx,9211,unaveraged = 1 µV? What is the minimum time [s] needed for the 9215 to record this number of data points? Correct the following sentence from a previous ME368 lab report: “The 9215 module samples much faster than the 9211 module, but it is also much noisier.”

  2. Quiz 4 ME368 Spring 2011 Open: book, notes, calculator Closed: laptop, wireless device, neighbor Consider the following recorded during calibration of a thermometer: Choose a reasonable fit function by inspection, and based on this choice, compute the standard error of the fit, Syx [K]

  3. Quiz 5 ME368 Spring 2011 Open: book, notes, calculator Closed: laptop, wireless device, neighbor Consider a spring with a spring constant, k equal to exactly 2 N/m. The spring is extended a distance x = 0.060 ± 0.005 m. The energy stored by the spring is given by E = ½kx2 Report the energy stored by the spring [J] with its uncertainty. Note: 1 J = 1 N-m

  4. Quiz 6 Closed: laptop, wireless device, neighbor Open: book, notes, calculator A single strain gage is mounted to a cantilever beam. During calibration, 10 data points were measured with each of 5 reference masses as shown. Associated x-from-y bands (at P = 95%) are shown: based on the plot, what mass (value with uncertainty at P = 95%) should be reported when a delta_R value of 4 ohms is measured? b) same as (a) but delta_R = 10 ohms? based on the plot, what is the smallest mass that can be detected (with 95% confidence) from a single measurement of delta_R?

  5. Now, Fourier transforms. Consider first analytical Fourier transforms. Some good online resources, e.g. www.falstad.com/fourier:

  6. Now, Fourier transforms. Consider first analytical Fourier transforms. Some good online resources, e.g. www.falstad.com/fourier:

  7. What if you have a non-standard signal, can’t just look-up the Fourier series, and/or can’t find a website that has your answer. Ex Consider a f=0.5 Hz, 2 Vpeak-peak sine wave, which can be mathematically expressed as V(t) = sin πt:

  8. What is the period, T, of this function in [s]? Now, imagine this signal was measured through a rectifier. The signal can now be expressed as V(t) = |sin πt|. Because the rectifier ‘flips’ the negative voltages into the positive half-plane, the signal appears as shown below: 3 • What is the period, T, of this signal in [s]? • What is the frequency, f, of this signal in [Hz]? • Find the first 4 terms of the Fourier series representation of this signal.

  9. comparison, see L19_Ex1.vi

  10. much more common to do this digitally: “Fast Fourier Transform” LabVIEW Spectral Measurements block

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