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Monitoring, measurement and control technology. Definition of data logging. Data logging – collecting data automatically from sensors over a certain period of time. Sensors. Used to detect and measure physical quantities Sensors include temperature, light, humidity, sound, pressure, etc.
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Definition of data logging Data logging – collecting data automatically from sensors over a certain period of time
Sensors • Used to detect and measure physical quantities • Sensors include temperature, light, humidity, sound, pressure, etc.
Sensors • Heat – investigating the cooling of a hot drink, control a heating system, fire alarms, cookers. • Light – Used to automatically come on when it is dark, used in plant growth environments, burglar alarms • Sound - Decibel readers in noise disputes, alarms. • Pressure – air pressure, barometric, depth of liquid • Humidity – measure moisture in the air • Passive Infrared Sensors (PIRs), detect movement, alarms
Data logging Important quantities that need to be set: • Logging period – total time over which all the readings will be collected • Logging rate/interval – how often the readings are taken • Location of sensors
How data logging works Data is collected from the sensors It can be sent to the computer using wires or wirelessly The computer processes the data (i.e., works out maximums, minimums, averages, etc.) The computer can also process the data by producing graphs and charts
Controlling devices • Actuators – mechanism that turns a device on or off, or moved, e.g. a motor. • Touch sensors – smart phones, PCs • Sequence of instructions to control devices – See Lightbot.
Main components of a control system • Sensors • Computer / processor • Output devices
Main components of a control system • Non feedback control systems. • Works regardless of feedback, e.g. does not receive any feedback as to the control sequence has been implemented. • Simple control systems • The computer decides whether to switch an output device on or off depending on the data it receives from a sensor • Examples include: Security lights, Automatic doors, Burglar alarms
Output devices controlled by control systems Actuators – these are devices such as motors Stepper motors – these turn in a series of small steps that you can control Bells/sirens – for alarms/warning sounds Heaters/coolers – for heating/air conditioning systems
Control Feedback loop INPUT PROCESS OUTPUT A A Feedback makes the control system more intelligent and useful. Read the example of a Control-Feedback loop on page 164