Abstract: A method for detecting the concentration of a specified gas contained in a mixed gas includes, in a pressure-type flow rate control device including a restriction portion, an upstream valve provided upstream of the restriction portion, and a pressure sensor for measuring the pressure between the restriction portion and the upstream valve, a step of flowing the mixed gas from the upstream side of the upstream valve in a state in which the pressure on the downstream side of the restriction portion is lower than the pressure on the upstream side of the restriction portion, a step of determining with a pressure sensor pressure drop characteristics occurring after the upstream valve is changed from an open to a closed state, and a step of determining the concentration of the specified gas in the mixed gas based on the pressure drop characteristics.

Abstract: A fluid flow path of a joining block includes a vertical flow path and a horizontal flow path. The joining block is constrained on a rail member so as to be capable of moving in a longitudinal direction. A fluid control device is supported by the rail member via the joining block and includes a screw hole, and a tightening bolt that has passed through a body of the fluid control device is screwed into the screw hole. A gasket between the joining block and the body is compressed between the body and the joining block by a tightening force of the tightening bolt. The screw hole includes the tip portion closed above the horizontal flow path and at least partially overlaps the horizontal flow path in a planar view.

Abstract: A screw hole of an upstream side joining block is formed only on an upstream side of a flow path port thereof in a longitudinal direction, a screw hole of a downstream side joining block is formed only on a downstream side of a flow path port thereof in the longitudinal direction and, between a guide part and an engaging part, an alignment mechanism aligns the positions of the upstream side and the downstream side joining blocks in a horizontal direction orthogonal to the longitudinal direction of the guide part to a center position of the guide part by using a portion of a reaction force that resists a bending force produced by the tightening force of a tightening bolt on a body and the upstream side and the downstream side joining blocks connected to each other.

Abstract: A fluid control apparatus having a fixing device is provided. A through hole of a lower level member includes a large diameter portion opening to an upper surface and a small diameter portion continuing from a lower side of the large diameter portion and opening to a lower surface. A fixing member includes a head portion that is to be inserted into the large diameter portion of the through hole of the lower level member, an upper shaft portion to be inserted into the small diameter portion of the through hole of the lower level member, and a lower shaft portion inserted at an upper end portion into a through hole of a supporting member. The lower shaft portion is provided with an engaging projection that engages a lower opening edge of the through hole of the supporting member and prevents the fixing member from dropping off the supporting member.

Abstract: To provide a lower member fixing device that eliminates the need for a fixation tool and reduces the time and effort for fixation, and a fluid control device provided with the lower member fixing device. A through hole of a lower member is formed by a large-diameter section opened in an upper surface and a small-diameter section continued from the lower part of the large-diameter section and opened in a lower surface. A fixation member includes a shaft section inserted into the small-diameter section of the through hole, a head inserted into the large-diameter section of the through hole, and a magnet section provided at a lower end of the shaft section. The support member is made of a magnetic substance and a recess into which the magnet section of the fixation member is fitted is formed in the upper surface of the support member.

Abstract: A fluid control apparatus having a fixing device is provided. A through hole of a lower level member includes a large diameter portion opening to an upper surface and a small diameter portion continuing from a lower side of the large diameter portion and opening to a lower surface. A fixing member includes a head portion that is to be inserted into the large diameter portion of the through hole of the lower level member, an upper shaft portion to be inserted into the small diameter portion of the through hole of the lower level member, and a lower shaft portion inserted at an upper end portion into a through hole of a supporting member. The lower shaft portion is provided with an engaging projection that engages a lower opening edge of the through hole of the supporting member and prevents the fixing member from dropping off the supporting member.

Abstract: To provide a lower member fixing device that eliminates the need for a fixation tool and reduces the time and effort for fixation, and a fluid control device provided with the lower member fixing device. A through hole of a lower member is formed by a large-diameter section opened in an upper surface and a small-diameter section continued from the lower part of the large-diameter section and opened in a lower surface. A fixation member includes a shaft section inserted into the small-diameter section of the through hole, a head inserted into the large-diameter section of the through hole, and a magnet section provided at a lower end of the shaft section. The support member is made of a magnetic substance and a recess into which the magnet section of the fixation member is fitted is formed in the upper surface of the support member.