Heater autotone control apparatus and method

A method of controlling a heater segment including the steps of

• sensing a temperature of a heater segment and at least one other heater segment,
• sensing a furnace temperature at a location corresponding to said heater segment,
• comparing the temperatures of at least two segments,
• developing a bias signal in accordance with said furnace temperature at said location corresponding to said heater segment and a result of said comparing step, and
• developing a control signal for said heater segment in accordance with said temperature of said heater segment, a set point signal and said bias signal.

A means for controlling a heater segment including

• means for sensing a temperature of a heater segment and at least one other segment,
• means for sensing a furnace temperature at a location corresponding to said heater segment,
• means for comparing the temperatures of at least two segments,
• means for developing a bias signal in accordance with said furnace temperature at said location corresponding to said heater segment and in response to said means for comparing temperatures of at least two segments, and
• means for developing a control signal for said heater segment in accordance with said temperature of said heater segment, a set point signal and said bias signal.