Title:
AIR FLOW RATE MEASURING DEVICE
Document Type and Number:
Japanese Patent JPH1151730
Kind Code:
A
Abstract:
PROBLEM TO BE SOLVED: To provide an air flow rate measuring device which is superior in characteristics to resist radio interference noise and is capable of maintaining high accuracy at all times. SOLUTION: An air flow rate measuring device is formed of a temperature sensing resistor Rh for measuring air flow rates, its driving circuit 70, an output voltage adjusting circuit 80, and a reference voltage circuit 90. The reference voltage circuit 90 is constituted of resistances 91 to 93 and a constant voltage circuit formed of zener diodes 94 to 96. At this time, if we let the zener voltages of the zener diodes 94 to 96 be VZ94 , VZ5 , and VZ96 , respectively, these zener voltages, a power supply voltage VB, and a reference voltage Vref are constituted so that an expression VB>VZ96 >VZ95 >VZ94 =Vref. As a zener diode is resistant to noise, it is possible to improve characteristics to resist radio interference noise without arranging a shield member or a radio noise filter. As it is resistant to reverse connection, it is possible to make an IC package, etc., compact and lightweight. Therefore, it is possible to provide an air flow rate measuring device which is reliable and superior in characteristics to resist radio interference noise at low cost with ease.
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Inventors:
TASHIRO SHINOBU
IGARASHI SHINYA
UCHIYAMA KAORU
IGARASHI SHINYA
UCHIYAMA KAORU
Application Number:
JP21352597A
Publication Date:
February 26, 1999
Filing Date:
August 07, 1997
Export Citation:
Assignee:
HITACHI LTD
HITACHI CAR ENG CO LTD
HITACHI CAR ENG CO LTD
International Classes:
G01P5/12; G01F1/68; G01F1/698; G01F15/04; (IPC1-7): G01F1/68; G01P5/12
Attorney, Agent or Firm:
Kenjiro Take
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