Analog to Digital Conversion
- Page ID
- 283114
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Note
The LabVIEW run-time engine needs to be installed on the computer (Windows only), and can be obtained for free from here (user registration required, also free): http://www.ni.com/download/labview-run-time-engine-2010-sp1/2292/en/
Simulations themselves can be obtained here: https://sites.google.com/a/cord.edu/labview-for-analytical-chemistry/
Run the ADC.exe application.
- Calculate the total number of possible values that the digital value can take for each of the following bit depths: 2-bit, 4-bit, 6-bit, 8-bit, 10-bit, 12-bit, 14-bit. For example, with 1 bit of resolution, there are 21 = 2 possible binary values.
|
Bit depth |
1 |
2 |
4 |
6 |
8 |
10 |
12 |
14 |
|---|---|---|---|---|---|---|---|---|
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Values |
2 |
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- For each of the bit depths in question #1, determine the minimum value and maximum value for each bit depth. For example, with a bit depth of 1 bit, the possible values are 0 and 1, so the minimum value is 0, and the maximum value is 1.
|
Bit depth |
1 |
2 |
4 |
6 |
8 |
10 |
12 |
14 |
|---|---|---|---|---|---|---|---|---|
|
Min. |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
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Max. |
1 |
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- Start with an Amplitude of 1.00 V, a resolution of 4 bits, and a range of ±10 V and have the simulation run continuously. As you increase the amplitude, describe how the analog and the digital signals change.
- What is the difference between an analog signal and a digital signal?
- Explain what happens in analog-to-digital conversion in such a way that a technologically illiterate grandfather could understand it.
- Assuming that you are digitizing an analog voltage between 0 and 5 volts, calculate the difference in voltage that corresponds to an increase in the raw count by 1 for each bit depth. Looking back at the number of values for each bit depth will be helpful.
|
Bit depth |
1 |
2 |
4 |
6 |
8 |
10 |
12 |
14 |
|---|---|---|---|---|---|---|---|---|
|
Voltage difference |
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- Reset to an Amplitude of 1.00 V, a resolution of 4 bits, and a range of ±10 V. How does the correspondence between the analog and digital signals change as you decrease the range? What is the significance of the Step Height?
- Reset to an Amplitude of 1.00 V, a resolution of 4 bits, and a range of ±10 V. How does the correspondence between the analog and digital signals increase the resolution (also known as increasing the bit depth)? Why does the step height change?
- Using an A/D converter with 12-bit resolution and an input range of ±10 V, at what analog signal amplitude do you begin to see distortion of the analog signal due to digitization?
- How does your answer change if you switch to 16-bit resolution and an input range of ±10 V?
- How does your answer change if you use 12-bit resolution but with an input range of ±1.25 V?
- Why does a higher resolution give a better digital representation of small analog signals?
- Why does a smaller input range give a better digital representation of small analog signals?
- If your signal also had noise present (and assuming that the amplitude of the noise is small compared to that of the signal), would you choose a smaller or larger input range to avoid recording it along with your signal? Would you choose a lower or higher resolution (bit depth) to avoid recording it along with your signal? What Analog-to-Digital Conversion issues arise as the amplitude of the signal gets smaller (while the noise amplitude remains the same)?
Contributors and Attributions
- An-Phong Le, Florida Southern University (ale@flsouthern.edu)
- Sourced from the Analytical Sciences Digital Library