Wk3 - Acquiring Data Flashcards
What are examples of physical phenomena that can be measured in IoT systems?
Examples include temperature, speed, position, illumination, force, torque, mass, blood pressure, precipitation, magnetism, acceleration, and distance.
What is a continuous signal? Provide an example.
Physical data that varies by time and is represented by a continuous, uncountable, infinite number of dependent variable points. Example: temperature.
What are the two steps involved in digitizing a signal?
- A sensor converts physical data (temperature, speed, distance, etc.) into an equivalent voltage vs. time signal.
- A digitizer (A/D converter) samples the voltage signal, converting it to a numerical value.
Why do sensors convert continuous signals to voltage vs. time signals?
Because computers are electrical devices. Sensors convert continuous signals into a form that an electrical digitizer can measure: voltage. Digitizers can only digitize voltage vs. time signals.
What is a discrete signal?
A countable number of dependent variable points; a finite number of points per unit time. It is created when a continuous signal is periodically sampled and converted to a digital representation.
What is an A/D converter?
An A/D converter takes a continuous voltage signal from a sensor and digitizes it into a digital word with a fixed number of bits.
What is the resolution of a 3-bit A/D converter with a 0-8V input range?
A 3-bit A/D converter with 8 possible outputs (2³) has a resolution of 1V per bit (8V/8 bits).
Why do sensors convert physical signals to voltage signals?
Because computers are electrical devices. Digitizers can only digitize voltage signals.
How can you improve the resolution of a system measuring temperature between 0°C and 100°C with an A/D converter?
Increase the number of bits in the A/D converter. For example:
- A 4-bit converter provides 6.25°C/bit.
- An 8-bit converter provides 0.39°C/bit.
What happens if a signal is under-sampled?
If a signal is sampled too infrequently, rapidly changing data can be missed, leading to inaccurate or incomplete representations of the original signal.
A/D converters are characterized by…
Bit length and conversion speed
How does the number of bits in an A/D converter impact resolution?
More bits = more resolution = higher cost.
For example, a 3-bit A/D converter has 8 possible outputs, while a 16-bit converter has 65,536 possible outputs.
What factors impact the selection of an A/D converter for a specific application?
The required resolution and conversion speed. Higher resolution and conversion speed = higher cost. Under-sampling (using a converter that is too slow) can result in lost data, while over-sampling (using a converter that is too fast) wastes money and resources.
