An induction heating tool that holds voltage or current supplied to the induction tank circuit constant and tracks changes in the other of voltage or current during each induction heating cycle. The disclosed induction heating tool exploits the fact that the resistance an attachment plate increases along with the temperature of the attachment plate. During an induction heating cycle, the attachment plate is magnetically coupled to a work coil and the resistance of the attachment plate is reflected to the circuit. Changes in the resistance of the attachment plate alter the pattern of energy delivery from the work coil to the attachment plate in a predictable way. Calculations accurately predict the temperature of the attachment plate over a wide variety of ambient conditions, including the presence of moisture at the membrane/attachment plate interface. The disclosed induction heating tool produces consistent results without calibration for ambient conditions.