An apparatus including a screen capable of separating solids from a liquid-solid mixture and a first probe disposed beneath the screen. A TEOS gas is supplied to start the film formation simultaneously when the RF output becomes 250 W, or while the timing is shifted. The port test routine is divided into threads such that execution time and switching overhead is minimized. A plate electrode is formed on the capacitance insulating film. The sheathed and flanged probe extends within the passageway such that a sensing element of the sheathed and flanged probe extends into the thermowell. In this way, by operating the DCDC conversion circuit after operating the power factor improvement circuit, the capacity of the capacitor can be reduced.