- Introduction to sampling
- Discrete units and digitization
- ADC and DAC
He is a wise man who does not grieve for the things which he has not, but rejoices for those which he has – Epictetus
Some dude thousands of years ago found a way to put down his thoughts on rock. Historians call these crude attempts symbolization. Artists call it art. Signal processing engineers call it sampling.
From the entire sequence of events that happened that day this dude tried to depict just one scene, frozen in his memory for some lost reason. Thousands of years later, our brightest minds scratch their heads trying to decipher what that dude was thinking.
What’s the lesson here? Events, or signals, can be sampled. In other words they can be broken up into bits. If our prehistoric photographer had captured more frames we might have a better idea of his vision, as it would closer represent our experiences. Or, he could have sampled his muse more precisely, like how a modern environmental portrait photographer will carefully position his subject against a chosen background to make a point. Or, he could have cloned the damn beast, like all living things do everyday to pass on the signal of life.
In its essence it is nothing but copy-paste. Numbers, symbols, alphabets, flags, T-shirts, DVDs, whatever – all created with the grand purpose of finding a form that an idea can take, with the sole requisite that this form can be replicated without loss.
When we use discrete values to represent a signal, instead of the whole shebang, we are said to be using a digital system – a system of digits – pieces – bits.
I said earlier that a non-continuous spacetime is inconceivable to man. Our experience and physiology forbids it. Yet think about this: our memory works in a selective way, with emphasis on ‘pieces’ of events. We are slaves of continuity, yet our mind invented sampling. Funny thing, our mind.
So what does Chinese whispers done digitally look like? Once the initial word is obtained, the first person writes down the word and rechecks with the source on its spelling. Once things are confirmed, the person passes on the piece of paper to the next person in the chain, and so on, until that paper reaches the last person. All the last person has to do is speak out the word on paper. In this example the first person is called an ADC, or Analog to Digital Converter, and the last person is called a DAC, or Digital to Analog Converter.
Digital systems were invented to preserve a signal’s integrity over the greatest possible distance or time. That’s about it, really.
- The central idea behind digitization is encoding in a language that can be replicated and passed around without loss.
- We can’t escape analog signals entirely, so we always need an analog to digital (ADC) converter and a digital to analog (DAC) converter.
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