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3.1 Hardware.computer_components Flashcards

1
Q

What is a memory cache?

A

High-speed memory external to the processor that stores data the processor will need again.

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2
Q

Define random access memory (RAM).

A

A primary memory unit that can be written to and read from.

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3
Q

What is read-only memory (ROM)?

A

A primary memory unit that can only be read from.

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4
Q

What is dynamic RAM (DRAM)?

A

A type of RAM chip that needs constant refreshing to retain its data.

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5
Q

Define static RAM (SRAM).

A

A type of RAM chip that uses flip-flops and does not require refreshing.

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6
Q

What does “refreshed” mean in the context of DRAM?

A

The process of charging a component to retain its electronic state.

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7
Q

What is programmable ROM (PROM)?

A

A type of ROM chip that can be programmed once.

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8
Q

Define erasable PROM (EPROM).

A

A type of ROM that can be programmed more than once using ultraviolet (UV) light.

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9
Q

What is a hard disk drive (HDD)?

A

A type of magnetic storage device that uses spinning disks to store data.

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10
Q

What is latency in computer systems?

A

The lag in a system, such as the time taken to locate a track on a hard disk.

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11
Q

What does it mean when a hard disk is fragmented?

A

Data is stored in non-consecutive sectors due to editing and deletion of old data.

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12
Q

What is a removable hard disk drive?

A

A portable, external HDD that connects via USB and is often used for backups.

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13
Q

Define solid-state drive (SSD).

A

Storage media with no moving parts, relying on electron movement for data storage.

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14
Q

What is electronically erasable programmable read-only memory (EEPROM)?

A

A ROM chip that can be erased and written to repeatedly using pulsed voltages.

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15
Q

What is flash memory?

A

A type of EEPROM suited for SSDs, memory cards, and memory sticks.

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16
Q

What is optical storage?

A

Storage media such as CDs, DVDs, and Blu-ray™ discs that use laser light to read/write data.

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17
Q

Define dual layering in DVDs.

A

A technique that uses two recording layers for increased storage capacity.

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18
Q

What is birefringence in DVDs?

A

A reading problem caused by laser light refraction into two beams.

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19
Q

What is binder 3D printing?

A

A 3D printing method that uses dry powder followed by a binding agent in two stages.

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20
Q

Define direct 3D printing.

A

A technique where the print head moves in x, y, and z directions to build layers of melted material.

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21
Q

What is a digital-to-analogue converter (DAC)?

A

A device that converts digital data into electric currents for motors, actuators, etc.

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22
Q

What is an analogue-to-digital converter (ADC)?

A

A device that converts analogue data (e.g., from sensors) into a format computers can understand.

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23
Q

What is an organic LED (OLED)?

A

A screen technology that uses electron movement to produce images without backlighting.

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24
Q

Define screen resolution.

A

The number of pixels horizontally and vertically on a screen.

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25
Q

What is a touch screen?

A

A screen that allows selection or manipulation using a finger or stylus.

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26
Q

What is capacitive touch screen technology?

A

A system where glass layers form a capacitor, and a touch changes the electric field.

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27
Q

Define resistive touch screen technology.

A

A system where touching causes a glass layer to meet a plastic layer, completing a circuit.

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28
Q

What is a virtual reality (VR) headset?

A

A wearable device that immerses the user in a virtual reality experience.

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29
Q

What is a sensor in computing?

A

An input device that reads physical data from its surroundings.

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30
Q

What is the primary function of memory in a computer?

A

Memory provides internal devices that the computer can directly access, acting as the user’s workspace or storing temporary and essential data for running the computer.

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31
Q

What is the purpose of storage devices?

A

Storage devices allow users to store applications, data, and files permanently, with the ability to modify or read them as needed.

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32
Q

Why does storage need to be larger than internal memory?

A

Users may need to store large files in large quantities such as music or photographic images, which require more capacity than internal memory provides. Not everything in secondary storage needs to be used at all times.

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33
Q

What is the benefit of removable storage devices?

A

They allow data to be transferred between computers or stored off-site to prevent data loss.

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34
Q

How has technology like ‘data drop’ and cloud storage changed storage needs?

A

They reduce the dependency on physical storage devices by enabling wireless transfer and remote data storage.

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35
Q

What is internal memory?

A

Components like registers (within the processor) and memory cache (external to the processor) used to store data for quick processor access.

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36
Q

What are the two categories of primary memory?

A

RAM (Random Access Memory) and ROM (Read-Only Memory).

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37
Q

What are examples of secondary storage devices?

A

HDD (Hard Disk Drive), SSD (Solid State Drive), removable devices like DVDs, CDs, Blu-ray discs, flash memory sticks, and portable HDDs.

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38
Q

What is primary memory?

A

Memory directly accessible by the CPU, including RAM and ROM, used to temporarily store applications and services.

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39
Q

Why is RAM called “random access”?

A

Any memory location can be accessed independently of the last used location.

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40
Q

What are the characteristics of RAM?

A
  • Can be written to or read from
  • Stores data, files, applications, or operating system parts currently in use
  • Volatile (loses contents when the computer is powered off)
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41
Q

How does RAM size affect computer performance?

A

Larger RAM reduces the need to overwrite data from secondary storage, speeding up operations.

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42
Q

What happens when RAM becomes full?

A

The processor accesses secondary storage more frequently, slowing down performance.

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43
Q

What are the two types of RAM technology?

A
  1. Dynamic RAM (DRAM): Requires constant refreshing.
  2. Static RAM (SRAM): Does not require refreshing and uses flip-flops.
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44
Q

How does RAM compare to secondary storage in access speed?

A

RAM has much faster access times than secondary storage devices.

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45
Q

What components make up a DRAM chip?

A

DRAM chips consist of transistors and capacitors. Capacitors hold the bits of information (0 or 1), and transistors act as switches to read or change the capacitor’s value.

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46
Q

Why does DRAM need to be refreshed?

A

Capacitors in DRAM lose their charge quickly and need to be refreshed every 15 microseconds to retain their values.

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47
Q

What happens if DRAM is not refreshed?

A

The capacitor’s charge leaks away, leaving all capacitors with a value of 0.

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48
Q

What are the advantages of DRAM over SRAM?

A
  1. Lower cost: DRAM is cheaper to manufacture.
  2. Higher capacity: DRAM has greater memory capacity.
  3. Lower power consumption: Under normal conditions, it uses less power compared to SRAM.
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49
Q

What are the disadvantages of DRAM compared to SRAM?

A
  1. Slower access time: DRAM has slower data access (60 ns vs. 25 ns for SRAM).
  2. Constant refreshing required: DRAM needs frequent recharging, consuming power under heavy access.
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50
Q

How does SRAM store data?

A

SRAM uses flip-flops to hold each bit of memory, eliminating the need for constant refreshing.

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51
Q

What are the advantages of SRAM over DRAM?

A
  1. Faster access time: SRAM is much faster (25 ns compared to 60 ns for DRAM).
  2. No refreshing needed: SRAM stores data without constant recharging.
  3. Used in cache memory: Ideal for high-speed operations like processor caches.
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52
Q

Why is SRAM used in memory cache?

A

SRAM’s speed allows it to store frequently accessed data and instructions, reducing the need to access slower DRAM.

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53
Q

What are the disadvantages of SRAM compared to DRAM?

A
  1. Higher cost: SRAM is more expensive to manufacture.
  2. Lower capacity: SRAM has less memory capacity.
  3. Potential for higher power usage: When accessed frequently, SRAM can consume more power than DRAM.
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54
Q

What is the typical access time for DRAM and SRAM?

A

DRAM: 60 nanoseconds
SRAM: 25 nanoseconds

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55
Q

Why is DRAM the most common type of RAM in computers?

A

Its lower cost and higher capacity make it suitable for main memory applications.

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56
Q

What is ROM and how is it different from RAM?

A

ROM (Read-Only Memory) is a permanent, non-volatile memory device that can only be read from, not written to. Unlike RAM, ROM retains its contents after power-off and is used to store data like the BIOS required for computer start-up.

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57
Q

What are the properties of RAM?

A
  • Temporary memory device
  • Volatile: Loses contents when power is off
  • Can be written to and read from
  • Stores data, files, programs, or parts of the OS currently in use
  • Increasing its size improves the operational speed of the computer
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58
Q

What are the properties of ROM?

A
  • Permanent memory device
  • Non-volatile: Retains contents after power-off
  • Data stored cannot be altered
  • Often stores BIOS and other data needed at start-up
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59
Q

What is a PROM?

A

A Programmable Read-Only Memory is a ROM chip that can be written to once using a PROM writer, which burns fuses in its matrix. PROMs are used in applications like mobile phones and RFID tags.

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60
Q

How does an EPROM differ from a PROM?

A
  • Stands for Erasable Programmable Read-Only Memory
  • EPROMs use floating gate transistors and capacitors instead of fuses.
  • They can be reprogrammed using ultraviolet (UV) light through a quartz window.
  • Commonly used for applications under development, such as new games consoles.
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61
Q

What are embedded systems?

A

Embedded systems involve microprocessors installed in devices (e.g., cookers, refrigerators) to enable efficient control of operations, often remotely via web-enabled devices.

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62
Q

What are the pros of embedded systems?

A
  • Small size, easy to fit into devices
  • Low cost to produce
  • Dedicated to one task, often without an OS
  • Low power consumption
  • Real-time operation with fast reaction to input
  • Reliable due to mass production
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63
Q

What are the cons of embedded systems?

A
  • Difficult to upgrade to new technology
  • Fault troubleshooting requires specialists
  • Interfaces, though simple, can be confusing
  • Vulnerable to hacking and viruses if internet-accessible
  • Often discarded rather than repaired, leading to waste
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64
Q

How is a PROM programmed?

A

A PROM is programmed using a PROM writer that applies electric currents to burn specific fuses in its matrix. This process is irreversible, allowing the PROM to be written to only once.

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65
Q

How is an EPROM erased and reprogrammed?

A

EPROMs are erased using ultraviolet (UV) light and reprogrammed through the same process, making them suitable for development applications.

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66
Q

Why are embedded systems considered efficient for real-time operations?

A

Embedded systems are dedicated to a single task, consume little power, and can react quickly to changes in input, making them ideal for real-time control.

67
Q

What is secondary storage?

A

Secondary storage includes non-volatile devices that are not directly accessible by the CPU. They allow data to be stored long-term and have larger capacities than primary memory but slower access times.

68
Q

What are the three main categories of secondary storage devices?

A
  1. Magnetic storage
  2. Solid-state storage
  3. Optical storage
69
Q

What types of data are stored in secondary storage?

A

Secondary storage holds applications, operating systems, device drivers, and general files like documents, photos, and music.

70
Q

How do hard disk drives (HDDs) store data?

A
  • Data is stored digitally on magnetic surfaces of spinning disks (platters).
  • Each platter has two surfaces, read-write heads, and tracks and sectors to store data.
71
Q

What is the function of read-write heads in an HDD?

A

Read-write heads access data on the magnetic surface of platters by moving between the centre and edge of the disk, enabling data retrieval or writing.

72
Q

What is latency in the context of HDDs?

A

Latency is the time it takes for a specific block of data on a track to rotate around to the read-write head, causing delays in data access.

73
Q

What happens to an HDD when data becomes fragmented?

A

Over time, due to deletions and editing, sectors become fragmented, leading to slower performance as the read-write heads take longer to access scattered data.

74
Q

How can HDD fragmentation be resolved?

A

Defragmentation software tidies up disk sectors, organising scattered data to improve HDD performance and reduce access time.

75
Q

What are removable hard disk drives?

A

Removable HDDs are external to the computer, connect via USB ports, and are often used for backups or transferring files between computers.

76
Q

What are the advantages and limitations of HDDs?

A

Advantages:

  • High storage capacity
  • Cost-effective for large-scale storage

Limitations:

  • Slower access times compared to RAM
  • Latency issues and fragmentation reduce performance over time
77
Q

Is an HDD a direct or sequential access device?

A

HDDs are direct access devices, but data within a given sector is read sequentially.

78
Q

What causes latency in an HDD, and when is it noticeable?

A

Latency occurs due to delays in aligning the read-write head with the correct data block. It is noticeable through system messages like “Please wait” or “Not responding.”

79
Q

How do solid state drives (SSDs) differ from hard disk drives (HDDs)?

A

SSDs have no moving parts and retrieve all data at the same rate, eliminating latency issues found in HDDs.

80
Q

How do SSDs store data?

A

SSDs store data as 0s and 1s by controlling electron movement in NAND chips, with transistors called floating and control gates forming non-volatile rewritable memory.

81
Q

What is EEPROM technology in SSDs?

A

EEPROM (electronically erasable PROM) uses NOR chips instead of NAND, offering faster operations.
Allows data to be read or erased in single bytes (vs. blocks in NAND).
Used in applications requiring fine-grained data access but is more expensive.

82
Q

What is the main distinction between NAND and NOR technology?

A

NAND technology is used in flash memory, which is cost-effective and handles blocks of data, while NOR technology is used in EEPROM, allowing byte-sized data access but at a higher cost.

83
Q

What are the advantages of SSDs over HDDs?

A

Advantages:

  • More reliable (no moving parts)
  • Lighter and thinner (ideal for laptops)
  • Lower power consumption and cooler operation
  • Faster data access
  • Do not need to “get up to speed”
84
Q

What is the main drawback of SSDs?

A

Limited longevity, known as SSD endurance, with conservative estimates of 20GB write operations per day for three years.

85
Q

Why are SSDs less common in servers?

A

Servers perform a large number of write operations daily, and SSDs’ limited endurance makes them less suited, though manufacturers are improving durability.

86
Q

Can existing data on a flash memory device be overwritten directly?

A

No, old data must first be erased before new data can be written to the same location.

87
Q

What are memory sticks (flash memories/pen drives), and what are their benefits?

A
  • Small, lightweight devices using solid state technology.
  • Connect via USB ports.
  • Suitable for transferring files and small backups (e.g., music or photos).
88
Q

How are memory sticks used to protect software from unauthorised use?

A

They act as dongles containing essential files for running software, preventing unauthorised access or copying as the software will not function without the dongle.

89
Q

What are the benefits of flash memory in general?

A
  • Portability
  • Reliability (no moving parts)
  • Ease of use with USB connectivity
90
Q

What applications are SSDs becoming more common in despite durability concerns?

A

Servers and cloud storage devices, as manufacturers improve durability.

91
Q

What are CDs and DVDs classified as, and how is data stored on them?

A

CDs and DVDs are optical storage devices where data is stored using a thin layer of metal alloy or light-sensitive organic dye and read/written with a red laser.

92
Q

How is data physically stored on CDs and DVDs?

A

Data is stored in ‘pits’ and ‘bumps’ on a single, spiral track that runs from the centre to the edge of the disk.

93
Q

What types of lasers are used in CDs and DVDs, and how do their wavelengths differ?

A
  • CDs use a red laser with a wavelength of 780 nm.
  • DVDs use a red laser with a shorter wavelength of 650 nm, allowing greater storage capacity.
94
Q

What is the significance of dual-layering in DVDs?

A

Dual-layering increases storage capacity by using two recording layers, separated by a transparent spacer and a thin reflector, with the laser focusing at a fractional depth difference for the second layer.

95
Q

How do DVDs achieve a larger storage capacity compared to CDs?

A

DVDs have smaller ‘pit’ sizes and narrower track widths, allowing more data to be stored on the surface.

96
Q

How does Blu-ray differ fundamentally from CDs and DVDs?

A

Blu-ray uses a blue laser with a wavelength of 405 nm, smaller ‘pits’ and ‘bumps’, and a single 1.1mm polycarbonate layer, avoiding birefringence and offering up to 5× the storage capacity of DVDs.

97
Q

What is birefringence, and why do Blu-ray discs not suffer from it?

A

Birefringence occurs when light refracts into two beams in a two-layer construction, causing reading errors. Blu-ray avoids this by using a single-layer design.

98
Q

What is the primary use of Blu-ray discs?

A

Blu-ray discs are mainly used for movies and games due to their high storage capacity and built-in encryption to prevent piracy.

99
Q

Why are CDs and DVDs still used despite being older technologies?

A

CDs and DVDs are used as backup systems for photos, music, and multimedia files, and for transferring files between computers. They are also used for distributing software in read-only formats.

100
Q

Why are DVDs and Blu-ray discs preferred over CDs for movies?

A

CDs lack the storage capacity needed for most movies, whereas DVDs and Blu-ray discs offer significantly higher capacities.

101
Q

What encryption feature does Blu-ray include, and what is its purpose?

A

Blu-ray discs come with a secure encryption system to prevent piracy and copyright infringement.

102
Q

What type of ink and printing method do laser printers use?

A
  • Laser printers use dry powder ink instead of liquid ink.
  • They print the entire page in one go, unlike inkjet printers.
  • Colour laser printers use four toner cartridges: blue, cyan, magenta, and black.
103
Q

How does a laser printer create text and images on paper?

A
  • Laser printers use static electricity to produce text and images.
  • A printing drum is charged positively, and a laser beam removes the charge in areas corresponding to the text/images.
  • Positively charged toner sticks to the negatively charged areas of the drum.
104
Q

What are the steps involved in printing with a laser printer?

A
  1. Data from the document is sent to the printer driver.
  2. The printer driver formats the data for the printer.
  3. The printer driver checks if the printer is available (not busy, off-line, or out of ink).
  4. Data is stored in the printer buffer (temporary memory).
  5. The printing drum is given a positive charge.
  6. A laser beam removes the charge in specific areas to match the text/images.
  7. Positively charged toner is applied to the negatively charged areas of the drum.
  8. Negatively charged paper is rolled over the drum, transferring the toner.
  9. The paper’s charge is removed after passing the drum to prevent sticking.
  10. The paper passes through a heated fuser, melting the toner to fix it permanently.
  11. A discharge lamp removes any remaining charge from the drum, preparing it for the next page.
105
Q

Why do colour laser printers differ from monochrome printers?

A
  • Colour printers use coloured dots (blue, cyan, magenta, and black) to create text and images.
  • The technology is different, but the printing process is largely similar.
106
Q

What are the key components of an inkjet printer?

A
  • A print head with nozzles that spray ink droplets onto paper.
  • Ink cartridges: either individual cartridges for each colour (blue, yellow, magenta, black) or a combined cartridge.
  • A stepper motor and belt to move the print head across the page.
  • A paper feed for automatic page loading.
107
Q

How does Thermal Bubble printing technology work?

A
  • Tiny resistors create heat, causing ink to vaporise and form a bubble.
  • The expanding bubble ejects ink onto the paper.
  • When the bubble collapses, a vacuum draws in fresh ink.
108
Q

How does Piezoelectric printing technology work?

A
  • A crystal at the back of the ink reservoir vibrates when charged.
  • This vibration ejects ink and draws in more ink for further printing.
109
Q

What are the steps involved in printing with an inkjet printer?

A
  1. Data is sent to the printer driver.
  2. The printer driver formats the data for the printer.
  3. A check is made to ensure the printer is available (not busy, off-line, or out of ink).
  4. Data is stored in the printer buffer (temporary memory).
  5. A sheet of paper is fed into the printer; sensors detect paper availability.
  6. The print head moves side to side, spraying ink to produce the text or image.
  7. After each pass, the paper advances slightly for the next line.
  8. The process repeats until the buffer is empty.
  9. The printer sends a request to the computer for more data if needed, continuing until the document is fully printed.
110
Q

What is 3D printing, and how does it differ from traditional manufacturing methods?

A
  • 3D printing creates solid objects by additive manufacturing, building layer by layer.
  • Traditional methods, such as subtractive manufacturing, involve removing material to form the object.
111
Q

What materials are used in 3D printing?

A

Powdered resin, powdered metal, paper, ceramic, or liquid polymers (hardened using lasers or UV light).

112
Q

How does direct 3D printing work?

A
  • Based on inkjet technology.
  • The print head moves left-to-right and up-and-down to build layers.
113
Q

How does binder 3D printing differ from direct 3D printing?

A

Unlike direct printing, binder printing uses two passes per layer:
- Sprays dry powder.
- Sprays a binder (glue) to solidify the layer.

114
Q

What advancements in 3D printing increase its capabilities?

A

Use of lasers and UV light to harden liquid polymers, enabling the production of diverse products.

115
Q

What are some applications of 3D printing?

A
  • Creating working, solid objects, such as artificial bone frameworks.
  • Producing items from materials like powdered stone or metal, paper, or ceramics.
116
Q

How is digitised sound converted into audible sound through a speaker?

A
  • Digital data passes through a Digital to Analogue Converter (DAC) to become an electric current.
  • The electric current is amplified to drive the loudspeaker.
  • The amplified current is fed to the loudspeaker, where it is converted into sound waves.
117
Q

What is the role of a DAC in sound reproduction?

A
  • Converts digital data into an analogue electric current to drive a speaker.
  • The conversion rate of the DAC is called the sampling rate.
118
Q

How does a loudspeaker convert electric signals into sound waves?

A
  1. Electric current flows through a coil wrapped around an iron core, turning it into an electromagnet.
  2. A permanent magnet is positioned near the electromagnet.
  3. Variations in the electric current change the magnetic field, causing the iron core to vibrate.
  4. The vibrating iron core moves a cone attached to it, producing sound waves.
119
Q

What determines the range of numbers a DAC can process? What is the range of numbers a 16-bit DAC can process?

A

A 16-bit DAC processes numbers between +32767 (2¹⁶-1) and –32768 (-2¹⁶), with the all-zero value ignored.

120
Q

How does a microphone convert sound waves into an electric current?

A
  1. Sound causes air to vibrate.
  2. The diaphragm in the microphone vibrates in response to air vibrations.
  3. A copper coil attached to the diaphragm moves in and out around a permanent magnet.
  4. The motion disturbs the magnetic field, inducing an analogue electric current.
  5. The current can be amplified, sent to a loudspeaker, or stored as sound.
121
Q

What happens to the electric current from a microphone when sent to a computer?

A

The sound card converts the analogue electric current into a digital signal for storage or processing.

122
Q

What are the two common types of microphone connections to a computer?

A

USB connection or wireless connectivity

123
Q

What are the two main technologies used in modern screens?

A
  • LCD backlit with LEDs
  • OLED (Organic Light Emitting Diode)
124
Q

How does OLED technology work?

A
  • Organic materials create flexible semiconductors.
  • Organic films are sandwiched between a metallic cathode and a glass anode.
  • When an electric field is applied, the films emit light, eliminating the need for backlighting.
125
Q

What advantages do OLED screens offer over LCD screens?

A
  • Do not require backlighting, allowing for thinner screens.
  • OLED is a self-contained system and does not rely on LCD technology.
126
Q

How do screen displays create colours?

A
  • Each pixel consists of three sub-pixels: red, green, and blue.
  • Varying the intensity of the sub-pixels generates millions of colours.
127
Q

What determines screen resolution?

A

The number of pixels viewed horizontally and vertically, e.g., 1680 × 1080 pixels.

128
Q

What are touch screens, and where are they commonly used?

A
  • Touch screens act as both input and output devices.
  • They commonly use LCD or OLED technology, often seen in mobile phones and tablets.
129
Q

How does a capacitive touch screen work?

A
  • Made of layered glass creating electric fields between plates.
  • Touch changes the electric current, and a microprocessor determines the coordinates.
130
Q

What are the benefits of capacitive touch screens?

A
  • Medium cost technology.
  • Good visibility in strong sunlight.
  • Multi-touch capability.
  • Durable and resistant to major impacts.
131
Q

What are the drawbacks of capacitive touch screens?

A

Only allows input from bare fingers or special styluses (in some versions).

132
Q

How does a resistive touch screen work?

A
  • Uses an upper polyester layer and a bottom glass layer.
  • Touch completes a circuit between the two layers, and coordinates are calculated by a microprocessor.
133
Q

What are the benefits of resistive touch screens?

A
  • Inexpensive technology.
  • Allows input using bare fingers, gloved fingers, or a stylus.
134
Q

What are the drawbacks of resistive touch screens?

A
  • Poor visibility in strong sunlight.
  • Does not support multi-touch capability.
  • Less durable; vulnerable to scratches and wears out over time.
135
Q

What is the primary function of a virtual reality headset?

A

To create an immersive experience by allowing users to explore virtual environments, for example, nuclear power plants, for safe planning and testing of modifications or repairs.

136
Q

How is video sent to a virtual headset?

A

Using an HDMI cable or a smartphone fitted into the headset

137
Q

What technology is used to display images in virtual headsets?

A
  • Two feeds are sent to an LCD/OLED display, sometimes using two screens (one for each eye).
  • Lenses reshape and focus the image for each eye to create a 3D effect.
  • 110° field of view for a pseudo 360° experience.
  • Frame rates of 60 to 120 images per second for realistic imagery.
138
Q

How do virtual headsets track user head movements?

A
  • Sensors such as gyroscopes or accelerometers.
  • LEDs combined with mini cameras for further monitoring.
139
Q

What type of sound technology do virtual headsets use?

A

Binaural sound (surround sound) to simulate realistic 3D audio effects from various directions and distances.

140
Q

How do infrared sensors in some headsets enhance VR headset realism?

A

Monitor eye movement, allowing depth of field adjustments (e.g., blurring foreground objects when focusing on distant ones).

141
Q

What are sensors, and what do they measure?

A

Sensors are input devices that measure physical properties such as temperature, pressure, or acidity.

142
Q

How is analogue data converted into a format usable by computers?

A

Through an Analogue to Digital Converter (ADC), which transforms physical values into discrete digital data.

143
Q

What is a Digital to Analogue Converter (DAC), and when is it used?

A

A device that converts digital data back into analogue signals, often used for controlling motors or valves.

144
Q

What are actuators, and what role do they play in control systems?

A

Actuators are electromechanical devices, such as relays, solenoids, or motors, that perform actions like opening valves or moving parts.

145
Q

What is an example of a digital actuator?

A

A solenoid (type of electromagnet), which can be used to operate a plunger or armature (e.g., in fuel injection systems) in a computer-controlled circuit.

146
Q

What is feedback in control systems, and why is it important?

A
  • Feedback occurs when the output affects the next input.
  • It helps the system adjust, such as changing a valve or motor to meet desired parameters.
147
Q

What are some applications of temperature sensors?

A
  • Control a central heating system.
  • Monitor/control chemical processes.
  • Monitor/control temperature in a greenhouse.
148
Q

How are moisture/humidity sensors used?

A
  • Monitor/control soil or air moisture levels in greenhouses.
  • Monitor dampness levels in industrial processes, such as paint spray booths in car factories.
149
Q

What are some applications of light sensors?

A
  • Switch street lighting on/off based on light levels.
  • Monitor/control light levels in greenhouses.
  • Turn on car headlights when it gets dark.
150
Q

How are infrared/motion sensors used?

A
  • Turn on car windscreen wipers when it rains.
  • Detect intruders in burglar alarm systems.
  • Count people entering or leaving buildings.
151
Q

What are some applications of pressure sensors?

A
  • Detect intruders in burglar alarm systems.
  • Measure weight, such as the weight of vehicles.
  • Monitor/control gas pressure in industrial processes.
152
Q

How are acoustic/sound sensors used?

A
  • Detect noise such as footsteps or breaking glass in burglar alarm systems.
  • Check for the sound of dripping liquids from a pipe.
153
Q

What are gas sensors used for?

A
  • Monitor pollution levels in rivers or air.
  • Measure O₂ and CO₂ levels in greenhouses.
  • Check for CO₂ or NO₂ leaks in power stations.
154
Q

What are some applications of pH sensors?

A
  • Monitor/control soil acidity or alkalinity.
  • Monitor pollution levels in rivers.
155
Q

What are some applications of magnetic field sensors?

A
  • Detect changes in devices like cell phones and CD players.
  • Operate anti-lock braking systems in motor vehicles.
156
Q

What is the difference between monitoring and control systems?

A
  • Monitoring systems only observe processes and alert when data is outside acceptable ranges.
  • Control systems actively intervene by adjusting valves, motors, etc., to bring the system back within acceptable parameters.
157
Q

What are the steps involved in a monitoring system?

A
  1. Sensors send signals to a microprocessor or computer.
  2. Signals are converted to digital format using an ADC if necessary.
  3. Data is analysed by comparing it with stored values.
  4. If data is outside the acceptable range, a warning is sent to a screen or an alarm is activated.
  5. The system continues monitoring without altering the process.
158
Q

What are the steps involved in a control system?

A
  1. Sensors send signals to a microprocessor or computer.
  2. Signals are converted to digital format using an ADC if necessary.
  3. Data is analysed by comparing it with stored values.
  4. If data is outside the acceptable range, the microprocessor sends signals to control devices (e.g., valves, motors).
  5. Outputs affect the next set of sensor inputs, forming a feedback loop.
159
Q

Give examples of monitoring applications for sensors.

A
  1. Monitoring a patient’s vital signs in a hospital, such as heart rate or temperature.
  2. Checking for intruders using a burglar alarm system.
  3. Monitoring the temperature levels in a car engine.
  4. Observing pollution levels in a river.
160
Q

Provide examples of control applications for sensors.

A
  1. Turning street lights on at night and off during the day.
  2. Controlling the temperature in a central heating or air conditioning system.
  3. Operating traffic lights at road junctions.
  4. Activating anti-lock brakes on a car when necessary.
  5. Regulating the environment in a greenhouse.
161
Q

What is the function of anti-lock braking systems (ABS) in vehicles?

Example: Sensor Applications in Vehicles

A
162
Q

Which type of sensors would be used in ABS?

Example: Sensor Applications in Vehicles

A

Magnetic field sensors

163
Q

How do magnetic field sensors in ABS work to prevent wheel lock-up?

Example: Sensor Applications in Vehicles

A
  1. A magnetic field sensor detects if one wheel rotates too slowly (indicating lock-up).
  2. The sensor sends data to a microprocessor.
  3. The microprocessor compares the rotation speed of all four wheels.
  4. If one wheel rotates more slowly, the microprocessor reduces the braking pressure to that wheel.
  5. The wheel’s rotational speed is increased to match the other wheels.

comp sci (15 decks)

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