Monitoring, measurement and control technology
Monitoring, measurement and control technology
Definition of data logging
Data logging – collecting data automatically from sensors over a certain period of time
Monitoring, measurement and control technology
Sensors
• Used to detect and measure physical quantities
• Sensors include temperature, light, humidity, sound, pressure, etc.
Monitoring, measurement and control technology
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
Monitoring, measurement and control technology
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
Monitoring, measurement and control technology
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
Monitoring, measurement and control technology
The advantages of data logging
Monitoring, measurement and control technology
The disadvantages of data logging
Monitoring, measurement and control technology
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.
Monitoring, measurement and control technology
Main components of a control system
• Sensors• Computer / processor• Output devices
Monitoring, measurement and control technology
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
Monitoring, measurement and control technology
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
Monitoring, measurement and control technology
Control Feedback loop
• Feedback makes the control system more intelligent and useful.
• Read the example of a Control-Feedback loop on page 164
INPUTINPUT PROCESSPROCESS OUTPUTOUTPUT AA
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