Chapter 5 : Input and Output Devices : Sensors Flashcards
How are temperature sensors used?
- Controls a central heating system
- Controls/monitors a chemical process
- Controls/monitors the temperature in a greenhouse
How are moisture/humidity sensors used?
- Controls/monitors the moisture levels in soil in a greenhouse
- Controls/monitors the humidity levels in the air in a greenhouse
- Monitors dampness levels in an industrial application
How are light sensors used?
- Switch street lighting on at night and off during the day
- Monitors/controls light levels in a greenhouse
- Automatically switch on a car’s headlights when it gets dark
How are infra-red/motion sensors used?
- Turn on the windscreen wipers on a car automatically
- Detect intruders in a burglar alarm system
- Count people entering/leaving a building
How are pressure sensors used?
- Detects intruders in a burglar alarm system
- Weigh things
- Monitors/controls a process where gas pressure is important
How are acoustic/sound sensors used?
- Pick up noise levels in a burglar alarm system
2. Detect noise of liquids dripping in a pipe
How are gas sensors used?
- Monitor pollution levels in a river or in the air
- Measure the oxygen and carbon dioxide levels in a greenhouse
- Check for carbon dioxide leaks in a power station
How are pH sensors used?
- Monitor/controls acidity/alkalinity levels in the soil in a greenhouse
- Pollution/environmental monitoring in rivers
How are magnetic field sensors used?
- Any application where detection of changes in a magnetic field is required
- Used in anti-lock braking systems in motor vehicles
What are the stages of scanning a document with a 2D scanner?
- The document is inserted into the scanner
- The scanner produces a bright light and illuminates the document
- A Scan Head moves across the document until the whole page. The image of the document is produced which is then sent to a lens using a series of mirrors. The lens focuses the document image
- The focused image now falls onto a charge couple device (CCD); which consists of a number of integrated circuits etched in silicon. The CCD is made up of thousands of light-sensitive elements (pixels). Each element creates an electric charge when light falls on it and so an electronic form is created. Software then concerts this data into a digital image
What kind of light do modern scanners use?
Xenon lamps
What is OCR software and what does it do?
It is Optical Character Recognition software and it allows scanned text to be converted into digital text so that it can be edited on a word processor
How does 3D scanning work?
As 3D objects have an x,y and a z coordinate the scanner takes images at several points along these three coordinates. A digital image which represents the solid object is formed
How are 2D scanners used in airports?
They are used to scan passports along side OCR technology which allows the images to be manipulated in various ways. In some airports they take photographs of the passengers and use facial recognition to compare the photos in the passport to the photo of the passenger
What data does facial recognition use?
- Distance between the eyes
- Width of the nose
- Shape of the cheek bones
- Length of the jaw line
- Shape of the eyebrows
