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 INPUT PROCESS OUTPUT A A