Title:
SPEED AND FLUID FLOW CONTROLLER
Document Type and Number:
WIPO Patent Application WO2004001515
Kind Code:
A9
Abstract:
A system and method for measuring fluid or gas flow rate, for the system where fluid or gas is pumped, such as gas monitoring instrument, via a conduit to a sensor. The flow of gas through a pump (14) is determined by measuring motor back emf which is proportional to motor (12) speed. The motor (12) speed is controlled by pulse width modulation "PWM" control (40) of the motor drive (38) voltage. The back emf is sampled (44) during intervals between the drive pulses applied to the motor (12). The sampling is done at selected, spaced-apart or infrequent intervals such as ones for every ten or once for every hundred motor drive pulses. In an instrument that uses a microprocessor (56) and analog-to-digital converter (50) to measure gas concentration, the same microprocessor (56) and converter (50) can provide the PWM control of the pump (14) in response to back emf generated by the pump motor between the drive pulses. The output of the analog-to-digital converter (50) that corresponding to the back emf, which in turn corresponds to the pump motor speed is compared via microprocessor (56) to set-point value of the desired pumpmotor speed. The processor then adjusts the PWM to remain the desired motor (12) speed.
Inventors:
BRISTOL L RODNEY
Application Number:
PCT/US2003/016938
Publication Date:
April 29, 2004
Filing Date:
May 30, 2003
Export Citation:
Assignee:
SCOTT TECH INC (US)
International Classes:
F04B49/06; F04B49/20; F04B51/00; F04D15/00; G01N1/24; G05B11/26; G05B21/02; G05D7/06; H02P6/18; H02P7/29; (IPC1-7): H02P7/628; H02P7/36; H02P5/408; F04B17/03
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