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Dependencies:   ADXL362 Lab7 mbed

report.txt@2:1dab962fe6f0, 2018-02-07 (annotated)

Committer:
dprowe
Date:
Wed Feb 07 22:47:01 2018 +0000
Revision:
2:1dab962fe6f0
report included

Who changed what in which revision?

UserRevisionLine numberNew contents of line
dprowe 2:1dab962fe6f0 1
dprowe 2:1dab962fe6f0 2 RESULTS:
dprowe 2:1dab962fe6f0 3 Our end results were fairly good in terms of expected output, given the difficulty
dprowe 2:1dab962fe6f0 4 of the task. When looking at our results of 1V sine waves, We noted marked
dprowe 2:1dab962fe6f0 5 decrease in output voltage of sine waves that had over 200Hz. We also noted
dprowe 2:1dab962fe6f0 6 some decreases at all increasing frequencies from the initial 100Hz. This is
dprowe 2:1dab962fe6f0 7 evidence that our low pass filter is functioning differently than an ideal low
dprowe 2:1dab962fe6f0 8 pass filter.
dprowe 2:1dab962fe6f0 9
dprowe 2:1dab962fe6f0 10 Difficulties:
dprowe 2:1dab962fe6f0 11 We had huge difficutlies with creating a sinewave that had accurate amplitude
dprowe 2:1dab962fe6f0 12 and frequency. We eventually achieved this simply by taking several data points
dprowe 2:1dab962fe6f0 13 from inputs of 5 - 70 micro seconds in delay, with ouputs of frequency from
dprowe 2:1dab962fe6f0 14 100Hz - 500Hz, in delay and using this data to create a function that would then
dprowe 2:1dab962fe6f0 15 work in the reverse. That is to say that we used the data points with frequency
dprowe 2:1dab962fe6f0 16 as an input and the wait time as an output to convert input frequencies to
dprowe 2:1dab962fe6f0 17 wait times that the STM board would then use to output the correct frequencies.
dprowe 2:1dab962fe6f0 18 This function was relatively accurate, and ended up being more accurate than the
dprowe 2:1dab962fe6f0 19 relatively simple and "exact" mathmatically correct function that converts
dprowe 2:1dab962fe6f0 20 frequency to delta time.
dprowe 2:1dab962fe6f0 21
dprowe 2:1dab962fe6f0 22 Expected vs Actual Results:
dprowe 2:1dab962fe6f0 23 Due to this somewhat "approximate" approach to creating the correct frequency,
dprowe 2:1dab962fe6f0 24 we obviously had some differences in our actual results when compared to our
dprowe 2:1dab962fe6f0 25 expected results. Our generated function was most accuate at low voltages and low
dprowe 2:1dab962fe6f0 26 frequencies, often achieving less than 1% error in the 1V and 100Hz range. When
dprowe 2:1dab962fe6f0 27 using higher frequencies, the function would usually output a frequency that was
dprowe 2:1dab962fe6f0 28 roughly 2-4% higher than our desired frequency. The voltage output was a similar
dprowe 2:1dab962fe6f0 29 story, with 1V being almost perfect, while 3V was usually off by around 3-5%.
dprowe 2:1dab962fe6f0 30 Because of these differences, and the nature of imperfect capacitors and resistors,
dprowe 2:1dab962fe6f0 31 our actual results when measuring our low pass filter were even further from
dprowe 2:1dab962fe6f0 32 the ideal results. We did note marked decrease in the output strength of
dprowe 2:1dab962fe6f0 33 frequencies over 200Hz, but not as sharp of decreases as expected. We also
dprowe 2:1dab962fe6f0 34 meausured a decrease in strength of the signal even when frequency was still below
dprowe 2:1dab962fe6f0 35 200Hz, which should only happen when very close to 200Hz. These differences
dprowe 2:1dab962fe6f0 36 must be attributed to many factors, the primary ones being slightly incorrect
dprowe 2:1dab962fe6f0 37 voltage and frequency outputs, imperfect wires, resistor, and capacitors, and
dprowe 2:1dab962fe6f0 38 some limitations in the measuring equipment.