Patent ID: 7752909

Claim:
A flow sensor for detecting the flow rate of a fluid to be measured flowing in a flow path, comprising: a heating means for heating a partial region of the outer wall surface of a pipe forming the flow path or for heating a particular region in the pipe; and temperature detecting means for measuring the temperatures of heat energy radiating regions for radiating the temperature influence from the heated region to the outside as heat energy, the heat energy radiating regions being regions on the upstream side and the downstream side of the pipe with respect to the heated region, wherein the temperature detecting means comprise an upstream-side non-contact temperature detecting means and a downstream-side non-contact temperature detecting means arranged near the outer wall surface of the pipe in a state of being not in contact with the outer wall surface, and the non-contact temperature detecting means can measure the temperatures of the upstream-side heat energy radiating region and downstream-side heat energy radiating region in a state of being not in contact with the outer wall surface of the pipe, the flow rate of the fluid to be measured flowing in the flow path is measured from the temperature difference between the temperatures of the upstream-side heat energy radiating region and downstream-side heat energy radiating region measured by the non-contact temperature detecting means or from the output caused by the temperature difference, and wherein an energy shielding means is provided between the heating means and the non-contact temperature detecting means to prevent the heat energy radiated from the heating means from being transmitted directly to the non-contact temperature detecting means, the energy shielding means comprising energy shield plates provided between the heating means and the non-contact temperature detecting means.