Looking for a low cost, easy to use digital temperature sensor? This DS1820 IC transistor like little guy is what you need.
The one wire Digital Temperature Sensor is great for measuring temperature in your projects. The DS1820 is a very small thermometer which can be easily hooked into the Arduino through any digital input! It is a 1 wire digital sensor in 3 pin TO-92 package and can give 9-12 bit precision with digital to analog converter. It has a multidrop capability which simplifies distributed temperature sensing applications.
The DS1820 can be powered by between 3.0V and 5.5V so you can simply connect its GND pin to 0V and the VDD pin to +5V from the Arduino. However, the DS1820 can also extract its power from the data line which means we only effectively need two wires to connect it up. This makes it great for use as an external sensor. Each DS1820 has a unique 64bit identification code which allows multiple DS1820 to function on same 1-wire bus thus it is simple to use one microprocessor to control many DS1820 distributed over a large area.