Data logging can be done manually by constant human observation. An example of this might be recording the temperature changes over the course of an hour in a centrally heated room using a timer, thermometer, pen and paper. However, using an electronic data logger is much more effective, accurate and reliable than taking periodic manual readings. It does the job of all the tools mentioned above, saving time and expense.
Data loggers vary between general purpose types for a range of measurement applications to very specific devices for measuring in one environment or application type only. It is common for general purpose types to be programmable; however, many remain as static machines with only a limited number or no changeable parameters. Electronic data loggers have replaced chart recorders in many applications.