Open loop control for spectrophotometer atomizer furnace

Heating apparatus for spectrophotometric analysis apparatus comprising:

• an electrical power source,
• a resistive heating element arranged to generate heat by being supplied as electrical energy from the power source, said power source being variable to enable control of the energy supply to the element, thereby controlling its temperature, and a control circuit operable to determine the total energy required to monotonically change the temperature of the element from an initial temperature to a selectable final temperature at a particular selectable rate, said total energy being dependent on the energy input to the heating element required to maintain the heating element at a constant temperature and also being dependent on said particular rate of element temperature change, said control circuit including storage means for storing data relating the heating element temperature within a temperature range to the energy input to the heating element at a constant temperature, both said initial temperature and said selectable final temperature falling within said temperature range, and said control circuit being operable to determine said total energy in part from said data in said storage means, and in part from the selected said particular rate of element temperature change, said control circuit being operable to generate an output signal representative of said total energy and to which the power source is responsive so as to control the energy supply by the power source to the heating element.