Abstract: A powder feeding system includes closed loop regulation of powder feed rate. A feed gas is discharged under constant pressure into an enclosed hopper. A valve is disposed to constrict a carrier conduit conveying powder in a carrier gas. A load cell measures the rate at which powder is flowing from the hopper through an intake orifice into the carrier conduit, and filtered flow rate signal is produced. A first controller produces a reference signal representative of the difference between a set point signal and the flow rate signal. A differential signal is produced corresponding to the pressure difference between the hopper pressure and a carrier conduit pressure taken between the intake orifice and the valve. A second controller produces a control signal representative of the difference between the differential signal and the reference signal. The valve is responsive to the control signal to proportionately constrict the carrier gas stream such as to regulate the powder flow rate.

Abstract: In a system and a method for measuring the rate at which powdered material flows from a container wherein a first analog signal representing the weight of the container is produced, the analog signal is differentiated to obtain a second signal corresponding to the flow rate and the second signal is passed through an adaptive filter. The adaptive filter includes a first low pass filter having a first time constant for producing a third signal and a second low-pass filter to produce a fourth signal.