Patent ID: 6935172

Claim:
A thermal type flow measuring device including a heating resistor (HF) disposed in a fluid (Q), upstream temperature measuring resistors (Ru 1 , Ru 2 ) disposed upstream of said heating resistor (HF) with respect to said fluid (Q), and downstream temperature measuring resistors (Rd 1 , Rd 2 ) disposed downstream of said heating resistor (HF) with respect to said fluid, thereby measuring the flow rate of said fluid, said thermal type flow measuring device comprising: a first bridge circuit including said upstream temperature measuring resistors (Ru 1 , Ru 2 ) and said downstream temperature measuring resistors (Rd 1 , Rd 2 ); a second bridge circuit including said first bridge circuit and said heating resistor (HF); and feedback control means (OP 1 , Tr) for heating said heating resistor (HF) in accordance with an output for keeping a balance of said second bridge circuit, wherein said upstream temperature measuring resistors or said downstream temperature measuring resistors are heated by said heating resistor, and the flow rate of said fluid is measured based on an output for keeping a balance of said first bridge circuit.