Collins Guide chapter 13
Data logging means collecting data from sensors, often for the purpose of scientific observation. Other data logging systems include process control systems and black box flight recorders in aircraft. Racing cars use data logging to record the state of key performance variables while the cars are running.
Sensors are input devices that can take readings from physical phenomena. Sensors can be read at intervals defined by a computer so they can be precisely timed with very short intervals (1 thousandth of a second or less) or very long intervals (once per hour or day).
Sensors include: temperature, light, heat, sound, pressure, acidity and humidity.
Sensors are often connected to an interface box, which may be battery powered so it can be used away from a computer, possibly for field observations (as in biology or ecology: remote data logging). The data captured by the sensors can be downloaded to a computer for processing in either dedicated software or in general purpose software such as a spreadsheet.
Data logging has various advantages, listed here.
Computer control is where a computer (or similar device with a micro-processor) is used to control a process such as an assembly line or an aeroplane. There are thousands of examples of devices that are controlled by a computer or embedded micro-processor.
Control systems typically include input from sensors and outputs to devices such as relays, motors, lights and buzzers. Simple systems can be put together from components such as light and pressure sensors (inputs) and lights and buzzers (outputs). An interface box such as the CoCo control box. The interface has to convert analogue readings from sensors into digital format, process them and then convert them to analogue form for output to the devices.
These simple systems for use by children are similar in operation to sophisticated systems in the real world for controlling nuclear power plants, nuclear missiles, aeroplanes and transportation systems such as the London Underground. An intermediate system might be a model railway.
Control systems often make use of feedback, which is where output from a system is fed back as input. One example of this is a heat control system: the output is in the form of heat, which is read by the heat sensors; the sensors detect when the heat exceeds a given level and send a message to the heating element to turn off until the temperature has fallen below the specified level. This is how a digital thermostat works. This kind of system might be used in a greenhouse as well as a domestic heating system. In a greenhouse system
A more sophisticated system is found in a fly-by-wire aircraft where sensors constantly monitor the flight of the aeroplane. The computers on the plane adjust the ailerons, flaps and rudder to keep it airborne and flying correctly. Modern fighter jets and commercial airliners would not fly without this system. A flight simulator attempts to simulate the behaviour of an aircraft in computer software by taking aeroplane behaviour and user input as streams of digital data that is processed by the simulator and output as movements on the screen.
Flowol is a control modelling system that uses on-screen mimics to allow users to create control simulations.