Physical parameters like humidity, temperature, pressure, and water level are measured and recorded using the data logger. Many of these devices are plug-in boards and use serial communication for connecting to the computer. Some are standalone devices that do not require a computer for its operation. They are available in various shapes and sizes with varying signal handling capabilities. Here are the components of this device:
  • Hardware, which includes sensors, signal conditioning hardware, and analog to digital converter.
  • A desktop computer.
  • Data logging software.

Data logger is given input using sensors. A sensor is a component which converts one form of energy into another. Usually, it converts physical quantities into corresponding electrical signals. These signals received from the sensors are analog signals and they must be converted into digital form using the analog to digital converter. These signals are sampled at a particular rate, which is known as sampling rate. This rate should be greater than the frequency of the original signal. The term 'sampling rate' implies the number of times the signal is measured.

The data logger is connected to the computer via a serial port. The electrical signals are used by the data logging software, which analyzes the signals and stores them. This software helps us to configure the time for which the sensors must sense the physical quantities. It also has an alarm system and a provision to set the sampling rate of the device. The procedure of using a data logger is as follows:
  • The device is fed the input of sensors like the thermocouples, strain gages, and accelerometers.
  • The software is configured according to the input sensor selected.
  • The parameters like the starting and stopping time and alarms along with other settings are configured using this software.
  • Data logging task is initiated and then the logged data is analyzed and stored using the same software.

Input Signals: The input signal is a physical quantity like the temperature, pressure, and relative humidity. However, some devices have programmable inputs. These inputs offer a provision of using the same data for any kind of physical parameters. Some physical quantities that can be measured are
  • Pressure (barometric, absolute, and gage).
  • Pulse (flow and speed).
  • Power quality of the voltage disturbances.
  • Temperature (zero and extreme hot).
Speed and Memory: The speed is determined by its sampling rate which depends upon the internal memory available. The internal memory is generally low, and hence the sampling rate of the logger is less.

Size: It is extremely compact and it can be a critical parameter in various data acquisition systems.

Power: These devices are powered externally. However, battery powered devices are also available.

Real-time Operation: The data is generally collected in real time and is stored in the computer.

Data recorders are used in various fields like testing of food and beverages, refrigeration and air conditioning systems, agriculture, aerospace, pharmaceutical, and research and development units. They are extensively required in industries for process management, auditing, verification of certain parameters, and for creating a system profile.