Data Logger: What is The Function of Datalogger in Geotechnical Field?
April 15, 2019
Large civil engineering projects like dams, tunnels, high rise buildings, bridges, deep excavations, often require safety monitoring during construction and also after construction for long term monitoring. This requires a large number of sensor installation at desired locations to monitor surface and subsurface parameters. Similarly, the environmental monitoring systems also require a large number of sensors to monitor environmental parameters. Data from these sensors is then analyzed for further actions.
The term datalogging means collecting data automatically from the installed sensors, for an assigned duration, at predefined intervals, without any physical/human intervention. The datalogger is an electronic device that is used to retrieve data automatically from the sensors installed in the field.
Datalogger is generally compact, battery enabled and has a digital processor as its heart. It has an inbuilt internal memory for data storage. One of the primary benefits of datalogger is its ability to automatically collect data 24 x 7 from a large number of sensors installed in the project. Once programmed, commissioned and activated, the datalogger can be left unattended to measure and record data from sensors for the duration of the monitoring period. This allows for a comprehensive, accurate overview of the risk assessment of the project being monitored.
Sensor connection to datalogger
SDI-12 serial digital interface is a smart protocol being used extensively with geotechnical and environmental sensors that allows these sensors to be connected to a variety of dataloggers. The beauty of the SDI-12 system is that only a single three conductor cable is required to interconnect all the sensors and the datalogger in a serial bus. SDI-12 is a multi-drop interface that can communicate with multi-parameter sensors. All the measured data is stored, together with the current date, time and battery voltage, as a data record in the internal non-volatile memory of the datalogger.
Dataloggers range from simple single-channel input to complex multi-channel instruments. Almost all types of parameters can be read by a single datalogger, like:
Strain, stress, load
Tilt/Inclinations
Displacement
Settlement
Deformations
Water pressure, water level
Temperature
Rainfall, wind velocity, humidity and other environmental parameters
Data transmission from datalogger
Generally, the dataloggers have a provision to interface with any computer, laptop or even mobile. They have their own designed software to activate datalogger to view and analyse the stored data at a larger scale. Some of the dataloggers have a local interface i.e. inbuilt keypads and LCD screen for display and act as stand-alone device. These are however, larger in size.
Today, the most commonly used dataloggers are the compact ones using a SIM (GPS/GPRS signal) for transmitting the collected data to any remote server. The server can be a private server or a cloud server.
Why to opt for dataloggers?
Whether it is geotechnical project or an environmental monitoring system, the monitored data is very critical of safety of the project or for environment. The data is needed accurately and instantly (real-time). Some more sophisticated instruments allow for cross-channel computations and alarms based on predetermined conditions. The advance dataloggers with data management software provide data on webpages, allowing numerous people to monitor a project remotely.
Dataloggers are used as an essential tool in the field of geotechnical instrumentation and environmental monitoring systems for automatic and continuous monitoring without physically being present on site. Construction staff, geotechnical consultants, project owners, research scholars etc. prefer using dataloggers because of following advantages:
Low cost
As the time has passed by, the cost of dataloggers has come down with an incredible advancement in the technologies developed. Users of dataloggers save time and money by using them unattended.
Unattended use
The advancement in the technologies have changed and options of power supply have increased like mains power, disposable batteries, rechargeable batteries, diesel generators, solar power, thermoelectric generators.
If used with internal batteries, the characteristic of longer battery life of portable dataloggers opens the window to use the dataloggers for longer duration even in a remote location unattended.
User friendly
Generally dataloggers are used by engineers, technicians and research scholars. It may sometimes be used by people with non-technical background. So to have a universal appeal, the user interface is designed to be user friendly. A user just needs to connect the sensors and configure it using the intuitive software without much hassle.
Reliability
Once activated, the datalogger starts logging the data for set duration, without any human error or delay providing factual and accurate real time data.
