Data loggers, today ,have become essential for automatic recording of various industrial scientific parameters using a variety of sensors and 4 to 20 mA isolated transmitters.Data value for Temperature /Humidity, pH /Conductivity, RPM, Load, Flow ,Voltage, Current, Power can be recorded with respect to time. The engineer / scientist need not manually use various meters and a stopwatch to measure and note various inputs. This additionally entails adding human error in reading both the measured values and the time .Data loggers remove possibility of all these errors. Using very high precision analog-to-digital converters ,the input signal is digitised and scanned respect to an accurate real time calender-clock. The microcontroller based system linearises the signal and conditions it to be stored in either solid-state memory or a pendrive .Pen drive can store almost infinite data. Finally the data can be downloaded in the format of an excel file or any other computer .This results in having a precision reliable data storage.