Speed and fluid flow controller
US6981402B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | May 30, 2003 |
| Grant date | Jan 3, 2006 |
| Priority date | — |
| Expiry date | May 30, 2023 |
Classification
- Technology area (CPC F)Mechanical Engineering; Lighting; Heating
- CPC primaryF04B2203/0213
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A system and method for measuring fluid flow rate in a system where fluid is pumped, such as a gas monitoring instrument where gas is pumped from a space such as a room or enclosure through a conduit to a sensor. The flow of gas through a pump is determined by measuring motor back-e.m.f. which is proportional to motor speed. In a system where motor speed is regulated by pulse width modulation of the motor drive voltage, the back-e.m.f. is sampled during intervals between the drive pulses applied to the motor, and in a further aspect the sampling is done at selected, spaced-apart or infrequent intervals such as once for every ten or once for every hundred motor drive pulses. Advantageously, in an instrument that uses a microprocessor and analog-to-digital converter to measure gas-concentration, the same microprocessor and converter can provide the PWM control of the pump, in response to the back-e.m.f. generated by the pump motor between the drive pulses. The microprocessor compares the output of the analog-to-digital converter, corresponding to the back-e.m.f., which in turn corresponds to the pump motor speed, to a set-point value, representative of the desired pump motor speed. T…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.