On October 23rd, 2014, we updated our
By continuing to use LinkedIn’s SlideShare service, you agree to the revised terms, so please take a few minutes to review them.
Sensors are used to take readings or measurements at regular intervals of their environment.
The sensors could be collecting data on a wide range of things such as temperature, humidity, pressure, wind speed, water currents, electrical voltage, pH readings etc.
The sensors may be either analogue or digital. If they take analogue readings, an Analogue to Digital Converter (ADC) will be needed to convert the signal into digital data which the computer can understand.
As the sensor takes a reading, the data is sent though a cable or wireless link to the data logger.
The data logger usually stores the data for a period of time before sending it in a large batch to a computer which will process and analyse it.
A data logger is often a hand-held battery-operated device which has a large amount of memory.
When a patient has had a major operation or is very ill, they may be in the Intensive Care Unit (ICU).
While they are in the ICU, they will be constantly monitored to make sure that their condition is stable and not deteriorating.
A heart monitor will take readings of their heart rate and pattern of beats. These readings will be displayed as digital numbers on the monitor itself and they will also be output to a continuous graph so that the doctors can pick up any changes over time.
Their breathing rate will be monitored and their level of oxygen measured. Alarms will be triggered if their oxygen level goes below a certain amount.
Their temperature will be measured at regular intervals to monitor whether they have an infection and if so, whether it is responding to treatment.
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 that 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. They display data collected by the sensors.
This data is logged and stored for later analysis by the engineers.
Also, output alarms can be set to alert the driver when certain conditions have been met.
Data can also be scrolled through by the driver pushing a button.
Water companies have to constantly monitor the acidity of the water in their reservoirs. They also monitor pollution, chemicals and the number of bacteria in rivers.
In order to do this:
The sensors take measurements of the water
An ADC converts the analogue signals into digital data
The data is sent to the data logger where it is stored until called for by the Water Board's computer.
On request, the digital data is transmitted to the Water Board's computer.
Special software (data logging software) takes the data and analyses it
The results of the analysis are presented as graphs and tables
The results are printed out
Remote data logging
Data often needs to be collected from places that are nowhere near a nice cosy office.
The data might need to be collected at all times of the day and night or during weekends when people might be away from work.
Data might also need to be collected from dangerous places such as volcanoes or from places where it is not practical or safe for a human to be, maybe deep in the ocean, in the upper atmosphere or even on other planets.
Remote data logging means that the sensors collect data 'out in the field' and pass it to a portable data logger.
The data logger then relays the data either wirelessly, by fibre-optic cables or possibly even by satellite, back to a computer ready for analysis.
The 'Logging Interval' is the period of time over which measurements are taken by the sensors.
If the measured value changes very rapidly then the time interval needs to be rapid as well, otherwise crucial events will be missed. On the other hand, if the data is going to change very slowly, then you would take readings much less often so that you do not get too much data.
Decades Melting of the ice cap Years Movement of glaciers Months Destruction of rain forest Weeks Growth of plants Days Soil dampness Hours Outdoor temperature Minutes Oven temperature Tenths of a second Heart beat Thousandths of a second Sound recording Typical Interval Data logging
Advantages and disadvantages
Data Logging can be used in remote or dangerous situations
Data logging can be carried out 24 hours a day, 365 days of the year
Time intervals for collecting data can be very frequent and regular, for example, hundreds of measurements per second
can be set up to start at a time in the future
No need to have a person present
Data logging is often more accurate because there is no likelihood of human error
If the data logging equipment breaks down or malfunctions, some data could be lost or not recorded
Equipment can be expensive for small tasks
The equipment will only take readings at the logging interval which has been set up. If something unexpected happens between recordings, the data will not be collected.