Measuring and testing – Volume or rate of flow – Thermal type
Patent
1988-08-03
1989-10-10
Goldstein, Herbert
Measuring and testing
Volume or rate of flow
Thermal type
731182, 364510, G01F 168
Patent
active
048723398
ABSTRACT:
A mass air flow measurement circuit is disclosed which provides a digital output without using a separate analog to digital (A/D) converter. This air flow measurement circuit includes a bridge circuit, wherein voltage is supplied to the bridge to control current through one or more sense elements in order to keep the temperature and resistances of the sense elements constant and balance the bridge. An electrical comparator is used to sense the balance of the bridge, and the output of the comparator is applied to an input port of a microcomputer. The microcomputer generates a rectangular wave pulse width modulated (PWM) signal whose duty cycle is increased or decreased in response to the output of the comparator. The PWM signal is then amplified and applied to the bridge to balance the bridge. Mass air flow is then calculated by multiplying the duty cycle of the PWM signal by a proportionally constant.
REFERENCES:
patent: 4043195 (1977-08-01), Hunting
patent: 4649745 (1987-03-01), Kondo et al.
patent: 4753111 (1988-06-01), Caron et al.
G. Gurtcheff et al., "Mass Airflow Sensor: Ambient Temperature Compensation Design Considerations", General Motors Corporation Publication, 4-6-86, pp. 4-11.
H. Fujisawa et al., "Electronic Controlled Gasoline Injector", Kouichirou Ojima, Tokyo 1987, pp. 1-7.
Sumal & Sauer, "Bosch Mass Air Flow Meter: Status and Further Aspects", Contained in the Compendium of Papers Entitled, "Sensors and Actuators SP-567" (SAE, 1984), pp. 19-28.
Gerhard Bruce
Schulman Bruce
Goldstein Herbert
NEC Electronics Inc.
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