Physical Quantity Detection Device

A physical quantity detection device configured to detect a physical quantity of a measurement target gas flowing in a main passage, the physical quantity detection device comprising:

• a housing arranged in the main passage;
• a sub-passage arranged in the housing;
• a flow rate detection unit arranged in the sub-passage;
• a circuit unit electrically connected to the flow rate detection unit;
• a circuit chamber arranged in the housing and accommodating the circuit unit;
• and a first introduction passage including one end open to the sub-passage and the other end open to the circuit chamber to communicate between the sub-passage and the circuit chamber, and configured to introduce pressure of the measurement target gas from the sub-passage to the circuit chamber, wherein
• the flow rate detection unit includes:
• a diaphragm including a diaphragm front surface exposed to the sub-passage and a diaphragm rear surface exposed to a closed chamber segregated from the sub-passage;
• and a second introduction passage including one end open to the circuit chamber and the other end open to the closed chamber to communicate between the circuit chamber and the closed chamber, and configured to introduce the pressure of the measurement target gas from the circuit chamber to the closed chamber, and
• the circuit chamber includes at least one or more protrusions arranged opposite an opening to which the other end of the first introduction passage is open.