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Thermal flowmeter with fluid descriminant function

  • US 6,681,624 B2
  • Filed: 10/15/2002
  • Issued: 01/27/2004
  • Est. Priority Date: 12/15/1999
  • Status: Expired due to Fees
First Claim
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1. A thermal flowmeter, comprising:

  • a flow rate detecting unit comprising a heating element, a flow rate detecting temperature sensing element and a flow rate detecting electroconductive heat transfer member extending into a fluid flow passage, which are disposed so as to enable heat transfer therebetween, said flow rate detecting temperature sensing element varying in electrical characteristic value in accordance with the flow of the fluid in the fluid flow passage through heat exchange with the fluid in the fluid flow passage which is carried out through the flow rate detecting electroconductive heat transfer member; and

    a fluid temperature detecting unit comprising a fluid temperature detecting temperature sensing element and a fluid temperature detecting electroconductive heat transfer member extending into said fluid flow passage, which are disposed so as to enable heat transfer therebetween, said fluid temperature detecting temperature sensing element varying in electrical characteristic value in accordance with the temperature of the fluid through the heat exchange with the fluid in the fluid flow passage, wherein the flow rate of the fluid is detected on the basis of the electrical characteristic value of the flow rate detecting temperature sensing element and the electrical characteristic value of the fluid temperature detecting temperature sensing element, and wherein said thermal flowmeter is adapted to determine a conductivity of the fluid between the flow rate detecting electroconductive heat transfer member and the fluid temperature detecting electroconductive heat transfer member to thereby effect a fluid discrimination.

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