Short note: Data logger

A data logger is an electronic instrument that automatically measures and records physical quantities (temperature, pressure, voltage, humidity, etc.) over time, at fixed intervals, and stores them for later analysis. It can work unattended for days or months.

Block diagram

 Sensors -> Signal    -> MUX -> S/H -> ADC -> Micro-  -> Memory
 (T, P, V)  conditioner                       controller   |
                                               |  ^        v
                                          Real-time   Display / PC
                                            clock     interface

Working

1. Sensors (transducers) convert the quantity into electrical signals.
2. Signal conditioning (amplifier, filter) brings the signal to a suitable level.
3. A multiplexer selects one channel at a time, and the ADC converts the analog signal into digital data.
4. The microcontroller adds the time stamp (from the real-time clock) and stores the data in memory (SD card, flash).
5. The data is shown on a display or transferred to a computer (USB, RS-232, wireless) for graphs and reports.

Advantages: accurate, unattended, saves manpower, many channels. Uses: weather stations, industrial process monitoring, laboratory experiments, cold-storage monitoring, environmental and power-system monitoring.