miniature thermal fluid flow sensors of the airfoil type are made in batch form by forming the thermal fluid flow sensors on a thin sheet of material and bonding the sheet over an array of duct structures and dicing the individual sensors and duct structures apart . in another embodiment , thin carrier sheet portions of a wafer bearing the thermal fluid flow sensors of the airfoil or grid type are supported by surrounding frame portions of the wafer . the wafer is diced to separate the individual sensing chips . the respective chips are mounted across respective fluid flow ducts . for the airfoil type sensor , portions of the frame are broken away for undisturbed flow over the thin carrier and sensor . in one thermal flow sensor configuration , a flow heater is disposed in between first and second thermal flow sensors in heat exchanging relation therewith . a third thermal flow sensor is disposed upstream of the others out of heat exchanging relation with the heater for operation of the heater at a certain temperature above that sensed by the third sensor . in the low flow regime , flow is measured by the difference between the outputs of the first and second sensors , whereas in the high flow regime , the power required to maintain the temperature of the heater serves as a measure of the flow .