Abstract: A blockage monitor for detecting a blockage in flow of particles includes a sensor body for mounting on a wall of the seed duct and defining a front face flush with the duct surface carrying both an LED light source for projecting light into the interior of the duct and a phototransistor arranged to produce an output signal proportional to the intensity of reflected light received which increases as a seed passes. A separate blockage module counts the output and uses an algorithm for comparing the count with a calibration count to determine whether there is a blockage of the duct. A power voltage is supplied to each sensor using two wires. A test of the sensor includes a pulse in the power voltage so as to generate a corresponding but delayed pulse in the light from the light source.

Abstract: A vertically oriented thermal processor supporting semiconductor wafers within a vertical processing chamber within a process tube about which a furnace heater is supported utilizes a model-base control target in combination with a heating control system configured to heat portions of the furnace in order to achieve a thermally uniform processing chamber environment. A furnace power controller implements a dynamic control system configured to achieve a desired uniform thermal distribution within the processing chamber during various processing cycles for semiconductor wafers. Preferably, the control system monitors thermal conditions within the chamber and compares the conditions with a desired thermal model of the furnace, and activates/deactivates one or more heater elements within the furnace in order to achieve a desired thermal condition within the processing chamber.