Abstract: A vortex flowmeter including a single optical fiber into one end of which a light signal can be transmitted from a source to the other fiber end where it is vortex modulated. Modulated light at the other end is then reflected to a receiver back along the same optical fiber. Relative movement between the other fiber end and a reflector serves to modulate the light signal. Embodiments are disclosed in which the other fiber end moves and the reflector is stationary. In the alternative case, the other fiber end is stationary and the reflector moves.

Abstract: An ultrasonic flowmeter arrangement has a pair of electroacoustic transmit/receive transducers located in opposite walls of a pipe, the transducers being longitudinally displaced and facing one another, thus forming a bidirectional transmission path oblique to the direction of fluid flow in the pipe. Each transducer is driven by a voltage controlled oscillator operating sometimes at nominally the same frequency. In one case the oscillator outputs are divided down separately to provide two different transmission frequencies. Filters apply to phase comparison means corresponding transmitted and received frequencies. The outputs of the phase comparison means provide feedback control signals for the oscillators. The oscillator outputs are fed to a mixing means to derive a difference frequency signal as a measure of the rate of fluid flow in the pipe.

Abstract: A fluid flow sensor of the vortex shedding type. Pressure differentials caused by shed vortices operate a piston system to vary the coupling between a pair of optical fibers thereby modulating light signals passing along the fibers.

Abstract: A flowmeter sometimes called ultrasonic, but sometimes not ultrasonic including two phase locked loops, a portion of each of which form a common path through amplifiers, an electronic attenuator with automatic gain control, a pulse detector, and a pulse or phase comparator. The pulse comparator, through switches, controls first and second voltage controlled oscillators on a time shared basis. First and second counters are connected from the first and second voltage controlled oscillators, respectively. The first and second counters supply transmission pulses to submerged first and second facing transducers, respectively, at different times. The voltage controlled oscillators are always driven until a later counter pulse coincides with a corresponding received pulse. Time sharing is, in part, accomplished by beginning energy propagation in opposite directions at successive times and before either pulse is received.