Compact data logger characteristics and block diagram

A compact data logger is a small, stand-alone, battery-powered logger with built-in sensors or inputs, memory and interface, used for measuring temperature, humidity, voltage etc. at remote places.

Characteristics

1. Small size, light weight, often pocket size and rugged (IP-rated).
2. Low power, battery operated for months or years (sleep modes).
3. Stand-alone operation: programmed once, runs unattended.
4. Few channels (1-8) with built-in sensors or standard inputs.
5. Non-volatile memory (flash/EEPROM) for thousands of readings.
6. Programmable sampling interval and start/stop triggers.
7. Real-time clock for time stamping.
8. Simple interface: USB/ serial/ wireless to a PC, with software for graphs and export; optional LCD.
9. Low cost, easy to install.

Block diagram

 Sensor(s) -> Signal conditioner -> ADC --+
                                           v
 Real time clock ----> Microcontroller <-> Flash memory
 Keys/LED/LCD <------> (with on-chip ADC) --> USB / Serial / BT
                           ^
              Battery + regulator (low power)

The microcontroller wakes up at the set interval, reads the sensor through the ADC, stores a time-stamped value in flash, and goes back to sleep. The stored data are read via USB into the PC.