A thick film NTC thermistor air flow sensor

Abstract

Two planar NTC thick film thermistors were placed in a rectangular air guide with a large cross section area and connected to opposite branches of a Wheatstone bridge to form air flow sensor. Thick film sensors used in measurements were printed on alumina using of thermistor paste NTC 3K3 - 95/2 in EI Iritel. NTC thermistor paste was composed of submicronic powder (mixture of Mn, Co and Fe oxides), 4% B/sub 2/O/sub 3/ and an organic vehicle. The most suitable planar NTC thermistor geometry for an air sensor was segmented type with an optimized surface value of 75/spl times/12/spl times/0.5 mm. It was used to cover part of an open air gauge and conduct a heat from flowing air. The resistivity difference obtained on the thermistors was compared with the volume velocity of air laminar flow at room ambient temperature and humidity.