In many areas of daily and technical life, making temperature measurements is the most important instrumentation task. ‘Intelligent’ digital sensors, which can do more than just output temperature readings, are winning more ground as complements to classical analogue techniques. An example of such a sensor is the Dallas Semiconductor DS1621.Naturally, the main job of a modern digital temperature sensor is to determine the current temperature. It does this by measuring its own temperature, which is nearly the same as the temperature of its surroundings, and converting this analogue temperature value into a digital word that it sends to a microcontroller via a serial interface. The user doesn’t have to worry about any of the analogue technology needed for calibration, amplification of the thermal voltage with opamps, linearisation of characteristic curves and so on, since all this is either done by the chip itself or can be easily set using software. External components are thus largely unnecessary.