PROBLEM TO BE SOLVED: To keep a desired cell internal pressure by constant and precise pressure control with detection precision similar to that in the case of initial detection free from an error by a pressure sensor 5 by preventing inside of a gas supply path 1a from becoming an always pressurized state though pressure control for keeping inside of a cell to be in a constant pressure state for a long period is carried out depending on the pressure sensor 5 which supervises the internal pressure of the gas supply path 1a.SOLUTION: The gas supply path 1a is provided with an openable and closable outside air flow-in port 8 which makes the outside air to flow in intermittently to refresh the inside of the gas supply path 1a.COPYRIGHT: (C)2007,JPO&INPIT【課題】 気体供給路1aの内圧を監視する圧力センサ5に依存して、セル内を定圧状態に長時間維持する圧力制御が行われるものでありながら、気体供給路1a内が常に加圧状態となることを回避し、圧力センサ5が、誤差のない初動時と同様の検知精度をもって、常に高精度の圧力制御により所望のセル内圧力状態に維持することを可能にする。【解決手段】 気体供給路1aに、外気を間欠的に流入せしめて気体供給路1a内をリフレッシュする開閉可能な外気流入口8を設ける。【選択図】 図1
