Patent ID: 8573051

Claim:
A flow rate measurement device, comprising: a main flow pipe having a main flow passage through which a gas passes; an orifice for limiting a flow of the gas in the main flow passage; and an auxiliary flow passage block provided with an auxiliary flow passage having one end communicating with a pair of introduction ports opened in the main flow passage on the upstream side of the orifice and the other end communicating with a pair of discharge ports opened in the main flow passage on the downstream side of the orifice, wherein the auxiliary flow passage includes: a pair of introduction flow passages having upstream ends respectively communicating with the introduction ports; an upstream auxiliary flow passage having both ends respectively connected to downstream ends of the introduction flow passages; a pair of discharge flow passages having downstream ends respectively communicating with the discharge ports; a downstream auxiliary flow passage having both ends respectively connected to upstream ends of the discharge flow passages; and a detection flow passage having an upstream end connected to the upstream auxiliary flow passage and a downstream end connected to the downstream auxiliary flow passage, the detection flow passage including a flow rate detection element, and wherein the upstream end of the detection flow passage is positioned on the upstream side of the main flow passage relative to the both ends of the upstream auxiliary flow passage, and the downstream end of the detection flow passage is positioned on the downstream side of the main flow passage relative to the both ends of the downstream auxiliary flow passage.