ELC Lab 4

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School

Thomas Edison State College *

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Course

201

Subject

Electrical Engineering

Date

Jan 9, 2024

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pdf

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Uploaded by kevinalandro

Kevin Austin ELC-201 Lab 4 1.1 Calculate the displayed Hex values for the following analog voltages: 0.5 V → 19 1.5 V → 4C 2.5 V → 80 3.5 V → B3 4.5 V → E6

1.2 Adjust the potentiometer so the input voltage at the ADC corresponds to the previous values. Record the output in Hex for each input. 0.5 V → 19 1.5 V → 4C 2.5 V → 7F 3.5 V → B3 4.5 V → 00

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1.3 Compare your calculated against your measured values. Comment on any differences. The values observed matched calculated values with the exception of 4.5V and 2.5V with the HEX output read 00 and 7F.

1.4 Substitute the potentiometer with an AC Signal with the following values: Peak Voltage: 2.5 V Offset: 2.5 V Frequency: 0.5 Hz 1.5 Run the simulation and observe the change in values in the Hex Displays. What happens when they reach FF or 00? Why do you think this happens? When the HEX display reaches FF or OO it increases and decreases. This represents the points where the AC input signal reaches its positive and negative peak. 1.6 Connect Channel 1 of the oscilloscope to pin D0 of the ADC and Channel 2 to pin D7. Run the simulation again. Explain the resulting waveforms Pin D0 signal is a square wave. 1.7 Change the frequency of the input signal to 40 Hz 1.8 Explain the reason for the staircase waveform seen for the reconstructed signal. The staircase waveform is the result of the digital signal being converted to analog.

1.9 Increase the frequency of the input signal to 150 Hz and comment on the resulting waveform. Is it still possible to recognize the analog signal? The resulting waveform is a ragged staircase but close to the analog signal. 1.10 Increase the frequency of the input signal until it is not possible to recognize the reconstructed signal. When does this happen? Don’t be surprised if this happens at a frequency much lower than predicated by the Nyquist criteria. Keep in mind that we are only sampling the signal with 8 bits, while the Nyquest criteria assumes ideal sampling. The analog signal became unrecognizable at 250 Hz which is lower than the 500 Hz that would represent the half sample frequency. Conclusion: In conclusion, I became more familiar with ADC using decimal and hex format as well as DAC using the o’scope to analyze the signal while using the information from ADC.

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