Patent ID: 7909504

Claim:
A drywell comprising: a receiver having first and second ends, the first end being exposed to ambient air and defining an opening therein for receiving a probe, the second end being relatively more insulated from the ambient air than the first end; a first heating element in thermal contact with the receiver proximate the first end and a second heating element in thermal contact with the receiver proximate the second end; a receiver sensor in thermal contact with the receiver proximate the second end, the receiver sensor being the only temperature sensor in thermal contact with the receiver; and a printed circuit board comprising a controller and an ambient sensor generating an ambient temperature reading, the ambient sensor being embedded in an integrated circuit mounted to the printed circuit board, the first and second heating elements, receiver sensor, and an ambient sensor in data communication with the controller, the ambient sensor producing an ambient temperature reading, the controller being programmed to monitor the temperature indicated by the receiver, to compare the temperature indicated by the receiver to a set temperature, to calculate a first heater power value based on the comparison, and to calculate a second heater power value according to the ambient temperature reading and at least one of the set temperature and the receiver temperature, the controller further programmed to power the first heater according to the first heater power value and power the second heater according to the second heater power value.