2.3 Data logging

Data Logging

Data logging systems use computers to automatically record data from sensors, without human intervention, over long periods of time. Data logging is used for the weather, Mars path finder and hospitals.

external image 220px-Mini_Datalogger_MSR165.jpgSmall datalogger with integrated sensors measuring temperature, pressure, humidity, light and 3-axis accelerationexternal image 220px-Data_logger_application_for_weather_station.jpg
Data logger application for weather station

Applications of data logging include:
  • Unattended weather station recording (such as wind speed / direction, temperature, relative humidity, solar radiation).
  • Unattended hydrographic recording (such as water level, water depth, water flow, water pH, water conductivity).
  • Unattended soil moisture level recording.
  • Unattended gas pressure recording.
  • Offshore buoys for recording a variety of environmental conditions.
  • Road traffic counting.
  • Measure temperatures (humidity, etc.)
  • Process monitoring for maintenance and troubleshooting applications.
  • Process monitoring to verify warranty conditions
  • Measure vibration and handling shock.
  • Tank level monitoring.

Advantages and Disadvantages of Data Logging

  • Data logging can be used in remote or dangerous places.
  • Data logging can be carried out 24 hours a day, 365 days of a year.
  • Time intervals can be frequent.
  • No need for a person to be present.
  • Data loggin is more likely to be more accurate than humans collecting the data. Reduction of the likelihood of human error.


  • If the equipment or system breaks down, data can be deleted or lost.
  • Some tasks may require expensive equipment.

The Data Logging Process

  1. Analog data is collected using a variety of sensors.
  2. The analog data is converted to digital data by an Analog to Digital Converter (ADC)
  3. The digital data is transferred to a computer for storage.
  4. The data is analysed and processed.
  5. (Optional) Alarms or alerts can be sounded if data is outside pre-determined ranges.
  6. Output such as graphs or tables are produced.
Analogue data is data which is measured, whereas digital data is counted. The process that is shown above is called digitization.

Real-Time Data Collection

Real-time data is when information is delivered immediately after collection. There is no delay in the timeliness of the information provided. Real-time data is often used for navigation or tracking.