Analog and digital data Skills: none IT concepts: analog to digital conversion, digital to analog conversion, sample rate, sample size, quality-file size trade off This work is licensed under a Creative Commons Attribution-Noncommercial- Share Alike 3.0 License.

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Start clocks Digital and analog clocks Which clock is digital? Which analog? Which clock is the closest analog to the physical world?

12:00:00 12:00:01 12:00:02 12:00:03 etc. A digital clock Digital data is discreet and jumpy, not smooth and continuous

Light level Pressure Sound waves Acceleration Position of a knob Orientation Proximity Gasses in the air Magnetic field Physical sensors → electric signals

For example, a microphone Sound waves Varying voltage

Analog to digital converter Computer Computers require digital data (150) (201) (199) … Analog data Digital data

The input is continuous, analog data Sample the signal at regular intervals S1 S2 S3... v1 v2 v7 S7...

Each sample produces a number v1 v2 v9

Each sample produces a number v1 v2 v9 A jagged approximation of the original, continuous signal

More frequent sampling results in a better fit

Each sample produces a number But How big (how many bits) is each number?

What time is it between seconds? Round off to the nearest second

60 steps 12 steps 4 steps More steps (higher resolution) means smaller round-off errors

Digitizing introduces round-off errors

More steps (intervals) between the minimum and maximum values means smaller round-off errors

Number of bitsNumber of possible steps … More bits per sample → more possible steps

The quality/file size tradeoff Increase sample rate → quality ↑ file size ↑ Increase sample size → quality ↑ file size ↑

Digital to analog converter Computer (150) (201) (199) … Computers can output analog data

Generate a somewhat jagged analog signal by approximating the value between samples with straight lines v1 v2 v9

Sound Light Flow rate Temperature Turn things on and off Electric signals → change physical world

A few questions S1 S2 S3... v1 v2 v7 S7... The value of sample 9 would be between the values of which two samples?

Without looking back, what two factors determine the quality or goodness of fit of a digitized signal to the original analog signal?

Where does this topic fit? Internet concepts –Applications –Technology (electronics) –Implications Internet skills –Application development –Content creation