The ICT Lounge
Section 5.5:
Analogue and Digital Data

This section focuses on different types of data, in particular, analogue data and digital data.

You will also see how and why we sometimes need to convert from analogue to digital data and vice versa.

Key Concepts of this section:

Understand the differences between analogue data and digital data .
Understand why it is sometimes necessary to convert between analogue and digital data.
Different types of data
Key Words:
Analogue, Digital, Digital Devices, Smooth, Digits, Binary.


There are two main types of data that we are going to discuss here:
# 1. Analogue Data
# 2. Digital Data
Analogue Data
"Analogue data use values that change very smoothly."

Smoothly changing hands of an
analogue clock.
A good example of this is an analogue clock. An analogue clock shows the time with a smoothly moving seconds hand. The change is continuous.
Sound is also a good example of analogue data. Sound waves change in a very smooth way.
This image shows you an example of a smoothly changing sound wave:
Analogue Devices
All analogue devices use analogue data. Examples of analogue devices include:
  • Microphone
  • Headphones
  • Loud Speaker
  • Sensors (temperature, pressure etc)


Digital Data
"Digital data jumps from one value to the next in a step by step sequence ."

Digital clocks 'jump' from one second to another.
A good example of this is a digital clock. A digital clock jumps from one second to another in clear steps. The change is not smooth or continuous.

Digital Devices
All digital devices use digital data. Examples of digital devices include:
  • Computers/Laptops/IPads
  • Mobile Phone
  • MP3 Player
  • Digital Camera


The name "Digital" is given to all devices that store and process data in the form of 'digits' (numbers).

These digits are known as 'Binary'.

What is Binary?



All computer data is really a number known as a Binary Digit (often shortened to just binary).

Binary is represented by the numbers 1 and 0.

Different combinations of these 1's and 0's are used to represent all the different kinds of data that can be stored and processed within a digital device (such as a computer).

For example:-
The word 'Hello' is stored as the binary combination of 0100100001100101011011000110110001101111

Analogue and Digital Conversion
Key Words:
ADC, DAC, Conversion.



Analogue values can only be used by analogue devices.

Digital values can only be used by digital devices.

If we want to use analogue values with a digital device or digital values with an analogue device we need to use data conversion.

There are two types of data converters:
# 1. Analogue to Digital Converter (ADC)
# 2. Digital to Analogue Converter (DAC)
Analogue to Digital Converter (ADC)


If we try to attach an analogue device (like a microphone) to a computer we will need to convert the analogue data to digital before the computer can use it.

In this example the ADC that converts the analogue values to digital would be the computer's sound card.

The microphone is used to pass the analogue sound waves through the ADC which will convert the sound from analogue to digital.
The ADC then passes the converted digital data into the computer where the sound can be stored and edited.

The image below will help explain this process:

Digital to Analogue Converter (DAC)


If we want to listen to digital music (like mp3's) we would need to attach an analogue device such as loud speakers or headphones to our computer.

Computer sound cards can perform both types of data conversion (ADC and DAC).

The computer will pass the digital sound values through a DAC (located on a sound card) which will convert the digital data to analogue.
The DAC then passes the converted anologue data onto the analogue loud speaker which we would then hear as sound waves.

The image below will help explain this process:

Another example of Data Conversion


Imagine we had a greenhouse and we wanted a way to control the temperature inside automatically. We could do this using a range of analogue and digital devices and ADC's/DAC's to convert all of the data.

This is how it would work:
#1. Analogue thermometer is used to gather smoothly changing temperature data
Analogue data is converted to digital using a ADC and fed into a digital computer
Computer reads the digital data and decides if the temperature is too hot or too cold
Computer sends data to a DAC built into a heater with 1 of 2 instructions:
If the temperature is too hot, the heater will be turned off
#### If the temperature is too cold the heater will be turned on.

Look at the image below for an example:

Click the above task and follow the instructions given on the sheet. Make sure that you complete all tasks on the sheet.

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