The ICT Lounge
 
Section 7.3:
Measurement Applications (Data Logging)
 
Computers are sometimes used alongside sensors to measure quantities such as pressure, temperature, radiation etc. This is known as 'data logging'.

Real-life examples that we will discuss include:
Key Concepts of this section:
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Understand how sensors can to used to gather measurable data .
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Know why computers can log and measure data more effectively than humans.
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Be able to discuss examples of how computers and sensors can be used to measure data .
1
Scientific Experiments
2
Electronic Timing
3
Environmental Monitoring
Sensors and Data Logging
Key Words:
Sensors, Data Logging, Automatic, Measure
What are sensors used for?
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Sensors are used to automatically detect and measure physical quantities.

If the sensor is connected to a computer, the computer can read the data coming from the sensor and log it at pre-set time intervals (hourly for example). This is sometimes called 'data logging'.

This allows us to see changes in the quantities (temperature increasing or decreasing for example)
Examples of Sensors
Temperature/Heat - Detect changes in temperature.
Light Sensors - Used to detect the brightness of light.
Sound Sensors - Measure the loudness of sound.
Humidity Sensors - Detect air moisture.
Infrared Sensors - Detect movement (Used in burglar alarms).

NOTE!
Most sensors read data in analogue format. Before the data can be used in a digital computer it must be converted using an analogue to digital converter (ADC)
Why use a computer to measure sensor data instead of a person?
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Computers are much better at reading and measuring quantity data taken from sensors for the following reasons:
Some environments are too dangerous for humans to take regular readings (arctic for example) .
More reliable
Computers will not forget to take the readings.
Accuracy
The computer will read the data more accurately than a person.
Response
time
Computers can react much quicker to data received. For example, if a patient's heart rate drops to critical levels an alarm could be sounded automatically.
Work longer
Computers can read data all day, every day without getting bored or tired.
Frequency of readings
Computers can read the data more frequently than humans can (1000's of times a second if needed).
Automatic Readings
No need for a human to be present. This frees people up to carry out other tasks.
Safer
Some environments can be lethal to humans. For example monitoring radiation levels in a damaged power station.
   
Examples of Computer Measurement Applications
Key Words:
Sensors, Log, Analyse, Analogue to Digital Conversion
The following examples show you how sensors and computers can be used to measure data:
Scientific Experiments
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Data logging can be setup to automatically monitor and record data generated by scientific experiments.
Sensor measuring the temperature of ice
 
Computer software could automatically analyse
the data
and produce charts.

Water Temperature Example:
Imagine you are conducting an experiment that records the temperature of water as it transforms from solid ice into hot steam. You would need to use the following:

  • Thermostat - to measure the temperature of the water
  • ADC - to convert the analogue temperature data into digital
  • Computer - to receive and log the digital temperature data
  • Software - to analyse the received data

How the experiment data would be logged
The thermostat would be used to measure the constantly changing analogue temperatures of the water.
The ADC is used to convert the analogue temperature data into digital (1's and 0's) which are then fed into the computer.
The computer and special software would then log the constantly changing temperature data and automatically analyse it in the form of charts.

NOTE!
The sensor would need to be told at what intervals to take temperature measurements. In our example the measurements are taken every minute.

 
Electronic Timing
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Computerised data logging can be used to accurately measure time.
Sprinters are separated by 1000's of a second and so timings have to be very accurate. Click to see race
 
Sensors and computers can be used alongside digital cameras which take up to 2000 images per second. This helps to accurately decide who crossed the finish line first.
Olympic 100 Metres Race Example:
In sprinting, generating accurate race times is important as, sometimes, first and second place can be separated by 1000's of a second. To accurately measure athlete's race times you would need:
  • Sound Sensor - to record when the race is started
  • Infrared Sensor - to record when the athlete crosses the finish line
  • ADC - to convert the analogue data from the sensors into digital
  • Computer and Software - to receive and log the digital data and calculate race time.
How the race time data would be logged
Race starter fires a starting pistol which tells each athlete that it is time to run. Sound from the pistol is sent to the computer and converted via ADC.
Sound sensor in the computer takes the signal from the starting pistol and computer starts each athlete's timer at exactly the same time.
The infra-red sensor projects a beam across the finish line which is broken as each athlete passes through.
The instant that the infra-red beam is broken by each athlete, a signal is sent to the computer which then stops the timer.
Software analyses all of the individual athletes timings and sorts them in order of fastest to slowest. This information is displayed on a board.
 
 
Environmental Monitoring
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Environmental monitoring is where data is collected to be used for purposes such as:
  • Weather forecasting
  • Water quality in rivers and streams
  • Levels of air pollution
  • etc.....
Weather stations monitor temperature, wind speed/direction, air pressure and humidity.
 
NOTE!
Weather station sensors constantly collect this data. 24 hours a day, 7 days a week, 365 days a year.

Weather Forecasting Example:
Weather stations contain lots of sensors which are used to gather a variety of different data. For example:
  • Thermometer - to measure temperatures
  • Humidity Sensor - to measure the amount of water in the air
  • Barometer - to measure air pressure
  • Anemometer - to measure wind speed
  • Rain Gauge - to measure the amount of rain fall over a certain period.
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These sensors would feed data into a computer which is then analysed by meteorologists (weather forecasters). The data allows the weather forecasters to make predictions about future weather.
 
Thermometer
Humidity Sensor
Barometer
Anemometer
Rain Gauge