Abstract: There is disclosed a method of monitoring the temperature of a cutting element in a sterile docking apparatus for splicing two sterile thermoplastic tubes together by using a resistor-heated cutting means, the method comprises (1) supplying a constant current to the resistor; (2) measuring the initial voltage of the resistor; (3) calculating, according to predetermined empirical relationship(s), the voltage, time or both required to achieve a desired cutting means temperature if the initial voltage is within a suitable range, (4) measuring repeatedly the voltage of the resistor and the time to determine whether (a) the voltage reaches the calculated voltage within a specified time frame or (b) the calculated time has been reached within a specified voltage range and (5) splicing the tubes with the cutting means if the time frame or voltage range is met. The method is also applicable to other resistor-heated elements in other devices having a constant heat load environment.