Chapter 3 - Hardware
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Is a thermometer a sensor+why
No, it is a tube filled with alcohol or mercury that can be read by a human eye in comparison to a scale, computers cannot see the level so it needs something else.
Whast sensor do you use to measure motion
Infra-red
What sensor do you use to measure temperature
Temperature sensor
Where would you use a pH sensor
In a pool
Where is an acceleromenter used
In a car
What are sensors
Input decives that can read or measure physical properties from their surroundings.
Explain real data+1 eg,
Real data is anologue in nature, meaning that there are infinite no of values and the data requires interpretation/best judgemnent from user Computers cannot make sense of real data Thermometer
What is an ADC
An Anologue Digital Converter Takes real life data/physical quantities and converts them to digital format/discrete digital values.
What is a DAC+eg of when they are used
Digital to anologue converter When a computer is used to control devices eg.valve Actuators are used
What is an actuator
A device that helps achieve physical movements by converting energy to mechanical force
What is feedback
When the output readings of a sensor are recieved by the microproccessor and may impact the next input to bring the system within the desired parimetres.
What are the 2 types of applications for sensors
Monitoring and control
Explain monitoring sensor use+eg.
If the new data recieved is outside the acceptable range,a warning message/alarm appears The microprocessor/computer has no effect on what is being monitored, they simply observe and notify Pollution in river
Explain sensor applications:control Eg.
If the new data recieved is outside the acceptable range, the computer/microprocessor sends signals to control aspects of the system/device. Output from the system affects the next set of inputs (feedback loop) Chemical process control(maitnaining pH)
What is the difference between active infra-red and passive infra-red
Active uses an invisible beam of infrared radiation that when broken changes the amount of radiation reaching the detector (wind screen wipers) Passive has sensors measure he heat radiation given off by an object (security alarm system)
Where are magnetic field sensors used
Anti-lock braking systems
What does the CPU consist of (3/4)
CU-control unit ALU- arithmetic and logic unit Registers and buses
What is a CPU
Central processing unit Responsible for execution/processing of all instructions and data in s computer Often installed as an integrated circuit on a microchip
What did John van Neumann do What features did it have
Developed a stored program computer in the 1940’s Concept of CPU CPU could access RAM directly Memory could store programs and data Stored programs were made up of data in sequential order
What are the main components of the CPU (3)
ALU-arithmetic and logic unit CU-control unit Registers
Purpose of ALU in the CPU
Allows arithmetic, logic and or operations to be carried out whilst a program is being run There can be more than one ALU to carry out specific functions
What does the CU in the CPU do
Reads instruction from memory/controls flow of information Address of location where instruction is found is stored in the PC (program counter) Generates command signals along control bus System clock is used to produce timing signals for^(without system would crash)
How is the instruction from the PC interpreted
Fetch-decode-execute cycle
Where + how does the CU access its data and programs
In the RAM/IAS(immediate access store) The CPU takes data and programs held in a backing store and temporarily puts them into RAM This leads to faster operations