iButton DESCRIPTION
The DS1921G Thermochron iButton is a rugged, self-sufficient system that measures temperature and records the result in a protected memory section. The recording is done ata user-defined rate, both as a direct storage of temperature values as well as in the form of a histogram. Up to 2048 temperature values taken at equidistant intervals ranging from 1 to 255 minutes can be stored.

SPECIAL FEATURES
Digital thermometer measures temperature in 0.5°C increments
Accuracy ±1°C from -30°C to +70°C. See EC table for accuracy specification
Built-in real-time clock (RTC) and timer has accuracy of ±2 minutes per month from 0°C to 45°C
Water resistant or waterproof if placed inside DS9107 iButton® capsule (Exceeds Water Resistant 3 ATM requirements)
Automatically wakes up and measures temperature at user-programmable intervals from 1 to 255 minutes
Logs up to 2048 consecutive temperature measurements in protected nonvolatile (NV) random access memory
Records a long-term temperature histogram with 2.0°C resolution
Programmable temperature-high and temperature-low alarm trip points
Records up to 24 time stamps and durations when temperature leaves the range specified by the trip points
512 bytes of general-purpose read/write NV random access memory
Communicates to host with a single digital signal at 15.4kbits or125kbits per second using 1-Wire® protocol