Airflow sensor and control circuit
US4884215A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 27, 1987 |
| Grant date | Nov 28, 1989 |
| Priority date | — |
| Expiry date | Feb 27, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01F1/698
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
The airflow sensor uses a flow sensing bridge having a thermal element which senses airflow as a function of electrical energy applied to the bridge. Energy is applied to the bridge to maintain the thermal element at a constant temperature and constant resistance. A differential amplifier monitors the balanced and unbalanced state of the bridge and controls the application of energy to the bridge to maintain a balanced state. A microcomputer with analog to digital converter senses the level of energy applied to the bridge and converts this energy level to a digital signal indicative of airflow. The raw digital signal is corrected using calibration lookup tables and thermal compensation correction tables in the microcomputer memory circuits. The microcomputer outputs a variable frequency signal indicative of the measured mass airflow. In the alternative to the differential amplifier, the bridge may be balanced using the microcomputer in a sample and hold voltage to current converter configuration.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.