Sensors and data logging

Sensors are used by computers to detect changes in various physical quantities, such as temperature, air pressure, electromagnetic fields, noise levels, sound, light etc, which are input directly into a computer via an interface. They are particularly useful for applications which are either too dangerous, or too tedious, for a human being to record data. They can operate 24 hours per day, 365 days per year. The use of sensors and feedback permits a much quicker reaction time than could be achieved by a human recording and processing data.

Data logging is the recording of data gathered via sensors over a prolonged period. Once it has been recorded, the data can be downloaded into a computer package such as a spreadsheet of analysis.

Examples of data logging include:

  • Measuring temperature in a heating systemn. When the temperature falls below a certain preset level, the boiler can be activated.

  • Recording the number of people passing through a turnstile. This is useful in situations where it is necessary to know the precise numbers of people in a shopping centre or stadium for safety reasons.

  • Measuring and logging the build-up of pressure in a volcano. In this case, it is simply too dangerous for a human to do this work.

  • Recording conditions on another planet, such as composition of the soil on Mars. At the present time, it is too expensive, impractical and dangerous to send a human.

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Advantages and disadvantages


Advantages:

  • Improves the accuracy
  • Collects information from scientific experiments and monitoring systems faster than humans
  • Displays the results in a graphical form
  • Prints out and analyses the results
  • Reeduces the error rate of the data processing

Disadvantages:

  • Storing data logging systems in the databases is very complex and hard to manage
  • It is hard to implement the data logging system/ configure it from the scratch
  • Tight integration with measurement hardware. Software has to be designed in order to work with the hardware.
  • High performance computers are needed in order to analyze the data

Examples of data-logging in use:

1 - In a hospital:

Montoring equipment in an intensive care unit
Montoring equipment in an intensive care unit
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.

2 - In an experiment:


In the video clip below you can see a ball being dropped. It would be impossible for a human to continuously and accurately measure the height of the ball as it bounces. Data logging equipment can record the movement and software can then plot it against time on a computer screen and store it for further analysis.
|||| The video clip shows the movement of a bouncing ball. The movement was recorded with data-logging equipment and displayed on a graph. ||

Video clip of a ball bouncing
Video clip of a ball bouncing
Graphical display of the ball bouncing
Graphical display of the ball bouncing

Advantages:
  • Many accurate reading can be taken per second.
  • The data is digital so it can be transferred straight to software which can display it or analyse it further.


Example of data logging


Sample question