The temperature can be controlled to 0.2ºC over the range – 25ºC to + 60ºC using a P.I.D. digital temperature controller, the CAL3200. Forced air over the heater and cooling fins and through the air duct in the rear wall ensures a uniform temperature throughout the cabinet. Defrost water drains via a pipe on the back of the cabinet to a heated tray underneath the cabinet where the water will evaporate. The cabinet also features an over temperature device which will switch off the fans, heating, cooling and illuminates a warning light if the set temperature is exceeded. The front door is double-glazed and contains a heating element to ensure that the glass door remains clear. When testing asphalt good temperature control is essential. Test data shows that a 1% change in temperature can cause up to 10% variation in stiffness results.