Data logging and recording is a common application. Data logging is the measuring and recording of physical or electrical parameters over a period of time or over depth measured by a sensor.
A DAT instruments data acquisition system (datalogger) is composed by several internal and external parts. Each part communicates with others in order to measure, display and record the signal.
A sensor (or transducer) is the electronic device that converts an input mechanical or physical value into an electrical output signal. The output can be analog (current: 0-20mA, 4-20mA; voltage: V, mV/V) or digital (on/off or serial communication). There are several kinds of sensors to measure: depth, length, pressure, flow rate, quantity, load, weight, current, voltage, speed, acceleration, inclination, rotation, GPS coordinates, temperature and many other values.
Not only a datalogger can measure and record data. It can also have outputs to control other devices, such as valves, motors, lights, etc... Outputs are activated over particular algorithms in function of input measured signals. An output can be analog (mA, V) or digital (on/off relay, on/off mosfet, frequency, serial communication, etc…).