monitoring, measurement and control technology. definition of data logging data logging –...

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