Data Logging & Control Systems Year 11

Data logging Data logging refers to collecting or gathering data over a period of time. Sensors are used to take readings or measurements at regular intervals. Data can be collected on a range of things such as: Temperature Water currents Traffic flow Wind speed If they take analogue readings an Analogue to Digital Converter (ADC) will be needed to convert the signal into digital data that the computer can understand.

Examples Racing Cars Some companies invest millions into developing state-of-the-art racing cars They want to know every aspect of how their car is performing so they can ensure the engine is calibrated correctly, the right amount of fuel is being delivered, the best speeds are being achieved etc. Digital electronic dashboards are used inside the cars and display data collected by the sensors/ This data is then logged and stored for later analysis by the engineers. Output alarms can also be set to alert the driver when certain conditions have been met.

Examples Hospital The sort of life-support systems found in intensive care units will make extensive use of data-logging equipment. The patients will have sensors attached to them which will continuously measure data such as temperature, blood oxygen level and heart rate. Advantages: 24 hour monitoring takes place without having to use a human operator who would need breaks, could lose concentration or could get tired and make mistakes. Alarms would be set off automatically if any measurements exceed a safe value. A continual record can be stored or printed out of everything that is being measured

Remote data logging Data often needs to be collected in remote areas such as volcanoes or space, this could be dangerous for humans and can be impractical. Another disadvantage is sometimes data needs to be collected at all times of the day and night or during weekends which can be difficult for humans especially if they are needed for long periods of time.

Data Once the data has been downloaded to a computer, spreadsheet software can use formulas to analyse the data and produce graphs/charts to display it more clearly. A simple analysis might just be to find the MAX, MIN and AVERAGE values of the data that is downloaded.

Advantages/ Disadvantages Increased accuracy is possible compare to measurements taken by humans Many measurements over VERY short time periods are possible and Regular measurements over VERY long time periods are possible Data can be collected from hostile environments Disadvantages If data logging equipment breaks data can be lost and equipment can be expensive Sensors must be carefully calibrated otherwise wrong readings can be taken

Control Systems A sensor is a device designed to measure some physical quantity in it’s environment. PIR sensor stands for Passive Infra Red sensors – they detect movement. Computer controlled greenhouse, what will happen when humidity falls? What will happen when temperature falls?:

Examples Security systems – PIR sensors can detect movement. Heat sensors can be used to detect human body heat. Automatic doors – Uses PIR to detect movement and open doors when someone comes near. Traffic control – Some traffic lights use traffic detection loops. In other words, they can detect when a car goes over that part of the road and can turn green. Car parking – Some cars use light sensors to sound a bell if you reverse too close to a wall. Some car parks can also take a photograph of a car’s licence plate. Greenhouses – Heat sensors can tell actuators (mechanical devices operated by control systems) to open a window if it becomes too hot. Robotics – PIR sensors in robots (programmable machines that perform a sequence of actions) can detect movement to avoid human injury. Robots can also spray cars, lift heavy objects, put together parts of machines and travel along track around a warehouse. Simulation – Flight and car simulators use actuators to move the simulated cockpit when a joystick or wheel is moved.