Abstract: A flow tube for a bidirectional flow meter includes a first flow chamber for generating a periodic pressure fluctuation whose frequency varies in dependence on the flow rate of fluid through the meter in a first direction. The flow tube also includes a second flow chamber for generating a periodic pressure fluctuation whose frequency varies in dependence on the flow rate of fluid through the meter in a second direction, opposite to the first direction. The first and second flow chambers are connected in series between an inlet port and an outlet port.

Abstract: A flow tube for a bidirectional flow meter comprises a first means (for example in the form of a first flow chamber) for generating a periodic pressure fluctuation whose frequency varies in dependence on the flow rate of fluid through the meter in a first direction; and a second means (for example in the form of a second flow chamber) for generating a periodic pressure fluctuation whose frequency varies in dependence on the flow rate of fluid through the meter in a second direction, opposite to the first direction; wherein said first and second generating means are connected in series between an inlet port and an outlet port.

Abstract: A fluid flow meter of the fluidic oscillator type and suitable for electrically conducting liquids, for example for metering domestic water supplies, comprises a feed back oscillator with magnets creating a magnetic field across at least one of the flow paths and a pair of electrodes detecting the resultant potential difference across the flow path. The frequency of the detected signal gives a measure of the flow rate and a counter of the cycles will give the total flow over a period.

Abstract: A fluid flow meter of the fluidic oscillator type and suitable for electrically conducting liquids, for example for metering domestic water supplies, comprises a feed back oscillator with magnets creating a magnetic field across at least one of the flow paths and a pair of electrodes detecting the resultant potential difference across the flow path. The frequency of the detected signal gives a measure of the flow rate and a counter of the cycles will give the total flow over a period.

Abstract: A magnetic flowmeter of the capacitively-coupled type includes low-input impedance detection circuitry which responds to a flow induced current signal that is related to the voltage induced at the electrodes by the intersection of the flowing fluid and a time varying magnetic field. An on-line measure of the electrode capacitance that is non-interactive with the flow induced current signal is accomplished by creating a voltage difference between the process fluid and the electrodes which causes a capacitance-related current to flow from the electrodes proportional to the value of the electrode capacitance as well as the rate of change of the magnetic field. In one embodiment the primary element and the detection circuitry are referenced to a different potential than that of the process fluid and the adjacent piping of the flow system.

Abstract: A flowmeter head is in the form of side-by-side channels of non-magnetic, electrically insulating material with the channels of very similar size. Sufficient precision of channel size is attained by boring the channels or by using drawn tube of closely controlled size. A radial electrode is provided in each channel, e.g. by drilling a fine hole in the channel wall and sealing a wire in. The electrode arrangement permits an applied magnetic flux to pass through first one channel, then the other. Earth electrodes are provided at the ends of each channel. An earth-loop free connection to a differential amplifier of a flowmeter apparatus is possible with the electrode configuration. The precision of the channel size improves common-mode accuracy and the earth-loop free connection reduces drift and noise.