There is a timer and thermometer built into the unit - you can display these details through the front LCD display panel. The sensor for the thermostat can be seen (along with the heat coil) in the base. The roaster provides constant heat but uses variable air flow to control the way the coffee roasts. To the left is a comparison of the temperature I programmed into the unit (yellow), the temperature as indicated by the onboard thermometer (blue), and the temperature I logged with a digital k-type thermometer (red). While the red graph would come closest to internal bean temperature, there is a consistent correlation between the three temperature indicators. For more on this, read my prototype review ! Also see our online i Roast Tip Sheet .
Full article: http://www.sweetmarias.com/prod.hearthwareiRoast.shtml