Differential pressure type flowmeter

Abstract

A differential pressure type flowmeter which can reduce a flow rate measurement error includes: a pipe (1); a laminar flow element (2) disposed within the pipe (1); a first absolute pressure sensor (3) measuring an absolute pressure (P1) of a fluid upstream of the laminar flow element (2); a second absolute pressure sensor (4) measuring an absolute pressure (P2) of the fluid downstream; a temperature sensor (5) measuring an ambient temperature (T) of the absolute pressure sensors (3, 4); a pressure calculation section (8) correcting an output signal from the first absolute pressure sensor (3) based on the temperature (T) to be converted into the absolute pressure (P1), and correcting an output signal from the second absolute pressure sensor (4) based on the temperature (T) to be converted into the absolute pressure (P2); and a flow rate calculation section (11) calculating a flow rate of the fluid based on the absolute pressures (P1) and (P2) calculated by the pressure calculation section (8). A film of the absolute pressure sensor (3) bearing absolute pressure (P1) and a film of the absolute pressure sensor (4) bearing absolute pressure (P2), and the temperature sensor (5) are integrated in one sensor chip.

Description

technical field [0001] The present invention relates to differential pressure flowmeters such as laminar flowmeters. Background technique [0002] A laminar flow meter utilizes a phenomenon in which a pressure drop accompanying fluid movement is proportional to a volume flow rate when the fluid flows in a laminar flow state in a pipe (see Patent Document 1 and Patent Document 2). The relationship between fluid passing through a laminar flow element and the resulting differential pressure ΔP is generally expressed by the following equation. [0003] Qm=ΔP×π×d 4 ×ρ / (128×μ×L)···(1) [0004] In formula (1), Qm is the mass flow rate, d is the flow path diameter of the laminar flow element, L is the flow path length of the laminar flow element, μ is the viscosity coefficient of the fluid, and ρ is the density of the fluid. [0005] Such as Figure 15 As shown, in the laminar flow meter, the absolute pressure sensors 101, 102 are arranged upstream and downstream of the laminar f...

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Problems solved by technology

[0016] But when Figure 16 ~ Figure 18 In the configuration shown, the measured pressure upstream and downstream of the laminar flow element 100 is affected by the temperature measurement error of the temperature sensors 103 and 104, so the differential pressure measurement error becomes large, and as a result, the flow rate measurement error may become large. sex

[0017] The above problems are not limited to laminar flow meters, but also occur in differential pressure flow meters using orifice plates, pitot tubes, etc. as differential pressure generating mechanisms.

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