What's the next phenomenon we will measure with our Metro? Temperature.
To do this we'll use a rather complicated IC (integrated circuit) hidden in a package identical to our P2N2222AG transistors, the TMP36. It has three pin's, ground, signal and power..and is easy to use.
It outputs 10 millivolts per degree centigrade on the signal pin (to allow measuring temperatures below freezing there is a 500 mV offset eg. 25 degrees C = 750 mV, 0 degrees C = 500mV). To convert this from the digital value to degrees, we will use some of the Arduino's math abilities. Then to display it we'll use one of the IDE's rather powerful features, the debug window. We'll output the value over a serial connection to display on the screen. Let's get to it.
One extra note, this circuit uses the Arduino IDE's serial monitor. To open this, first upload the program then click the button which looks like a square with an antennae.