Patent ID: 8627717
Filing Date: 2014-01-14
Classification: G01F

Abstract:
1. A thermal flow sensor comprising: a semiconductor substrate; a cavity portion provided in the semiconductor substrate; a dielectric film provided on the semiconductor substrate so as to cover the cavity portion; a thin layer area formed as a result of the dielectric film covering the cavity portion; a heating resistor provided in the thin layer area on the dielectric film; a first temperature-sensitive resistor provided in the thin layer area on the dielectric film, a resistance value of the first temperature-sensitive resistor varying depending upon temperature; a heating controller that controls temperature of the heating resistor on the basis of temperature of the first temperature-sensitive resistor; a second temperature-sensitive resistor provided near the heating resistor, a resistance value of the second temperature-sensitive resistor varying depending upon temperature; and a flow rate detector that detects a flow rate of a fluid on the basis of temperature of the second temperature-sensitive resistor, wherein the heating controller controls the temperature of the heating resistor on the basis of a first reference temperature, which is a target temperature of the first temperature-sensitive resistor, and a second reference temperature, which is an escape temperature of the first temperature-sensitive resistor.