Abstract: An analog current-to-frequency converter which produces output pulses whose repetition rate depends on the current value. Included in the converter is an operational amplifier having an inverting input to which is applied a negative input voltage whose magnitude is proportional to the current value. The amplifier functions as an integrator which yields a positive output only when the voltage at its inverting input is negative. The integrator output is so coupled to the input of a one-shot as to cause the one-shot to generate an output pulse each time the integrator output crosses over from negative to positive. A NOR gate coupled to the one-shot acts to activate a switch only when the integrator output goes positive, the activated switch applying a positive reference voltage to the inverting input of the integrator through a balance resistor, thereby initiating a swing from negative to positive until a point is reached at which the integrator output goes from positive to negative.

Abstract: An electromagnetic flowmeter for metering the flow rates of fluids of low conductivity, the flowmeter including a non-magnetic spool within which is disposed a pair of electrode assemblies at diametrically-opposed positions embedded with an insulating layer molded against the inner surface of the spool. Each assembly is constituted by a curved measuring electrode plate and a curved shielding electrode plate concentric with the spool, the face of the measuring electrode plate being exposed. Received within the insulating layer and covering the faces of the measuring electrode plates is a tubular liner made of dielectric material whose properties are appropriate to the fluid being metered, the liner defining a flow conduit for the fluid.

Abstract: A technique for stabilizing an insulating liner formed of thermoplastic material which is injection molded onto the inner surface of a metal spool having a cylindrical body provided with end flanges, an annular gap being created between the liner and the spool body due to differential shrinkage between the liner and the body as the molded liner cools and solidifies. In order to fill this gap to prevent a change in the inner diameter of the liner when the liner is subjected to the pressure of a fluid flowing therethrough, the spool body is provided with ports which extend between the exterior and interior surfaces thereof. These ports are sealed during the injection-molding process by removable plugs. After injection-molding, the plugs are removed and a thermosetting resin is introduced into one of the ports until the gap is filled as evidenced by the fact that the resin begins to rise in the other ports, the resin then being cured to solidify the filler.

Abstract: A free chlorine analyzer including a probe immersible in chlorinated water having oxygen dissolved therein, the analyzer being adapted to continuously and accurately measure the concentration of free chlorine in the water without regard to its oxygen content. The probe includes a noble metal measuring electrode, an oxidizable metal counter electrode and an electrolyte which in combination with the electrodes defines an electrochemical cell whose output current depends on the amount of the chlorine passing into the cell through a diffusion membrane permeable to this gas. The cell is connected through one or more serially-connected diodes operating in the forward direction to an output resistor across which is produced a voltage that depends on chlorine concentration. The voltage drop across the diodes impresses a potential on the cell which causes it to operate in a current limiting range and renders it insensitive to the oxygen content of the chlorinated water.

Abstract: An ultrasonic, echo-ranging instrument for measuring the level of liquid in an open channel or tank. The instrument includes a transducer disposed at a fixed position directly above the liquid surface, the nature of the gaseous environment therebetween determining the velocity of ultrasonic energy propagated therethrough. The transducer is excited to emit periodic pulses which are intercepted by the liquid surface and by a reference point a fixed distance from the transducer to produce both reference and liquid echo pulses that are returned to the transducer and detected thereby. The respective transit times of the reference echo and the liquid echo pulses are determined, and the ratio between these transit times is computed to provide an output representing the level of liquid independent of changes in the gaseous environment. To ensure accurate readings, the reference echo and liquid echo pulses from the transducer are fed to a single automatic gain control circuit whose operation is time shared.

Abstract: A highly compact electromagnetic flowmeter unit interposable between the flanged ends of upstream and downstream line pipes for metering fluid passing through the line. The flowmeter is constituted by a cylindrical casing of ferromagnetic material within which a pair of electromagnet coils is supported at opposed positions along a diametrical axis normal to the longitudinal axis of the casing, the longitudinal axis passing through the central flow passage of an annular pressure vessel. The vessel, which is formed of high-strength insulating epoxy material, is molded within the casing and encapsulates the coils as well as a pair of pre-cast electrodes formed of conductive epoxy material disposed at diametrically-opposed positions with respect to the flow passage along a transverse axis at right angles to the coil axis to define a unitary structure. The epoxy of the electrodes is compatible with that of the vessel, whereby a fluid-impermeable bond is formed therebetween.

Abstract: A hybrid sensing system for a vortex-type flowmeter in which fluidic oscillations are generated at a frequency depending on the flow rate of the fluid being metered, the flowmeter being operative throughout a wide range of frequencies. The system includes both a thermal sensor whose signal, which is applied to a first pre-amplifier, has an amplitude that is relatively high in the low-frequency portion of the meter range, and a force sensor whose signal, which is applied to a second pre-amplifier, has an amplitude that is relatively high in the high-frequency portions of the range. The signal amplitudes of the pre-amplifiers are compared to effect control of a selector switch which acts to couple the pre-amplifier yielding a greater output at the prevailing frequency to a trigger generating pulses at a rate determined by this frequency and indicative of flow rate.

Abstract: An electromagnetic flowmeter provided with a field coil to create a magnetic field across the flow tube through which the fluid to be metered is conducted, the flowmeter having an excitation circuit adapted to supply periodic current to the coil in alternating polarity and to maintain the intensity of the current at a constant level. The circuit includes a polarity-reversing commutator whose input is connected to a current supply source through an actuatable switch, and whose output is connected through a cable to the coil. The switch is actuated by a switching regulator generating actuating pulses whose duty cycle is modulated in accordance with an applied control signal. A reference signal is derived from the field coil that is proportional to varying current flow therethrough and is compared with a set point to produce a control signal that depends on the difference therebetween.

Abstract: A system operating in conjunction with a computer whose central processing unit is adapted to process data fed thereto by a variable data source to yield at its output port, parallel binary-coded data having an even number of bits which are supplied to a data bus. The system is coupled to the data bus and includes a series of binary rate multipliers to convert the binary-coded data to a conversion frequency which is divided to provide an output frequency in a range suitable for indicating the variable data and which is at the same time converted to an output current proportional to the variable data. The output frequency and output current are electrically isolated from the computer and its associated data source to avoid any interaction therewith.

Abstract: Each guide member of a fluidic oscillator has a diverter which acts to split the flow from the power nozzle into a control stream that is diverted toward the inlet of an associated feedback path and an output stream that is directed toward an output duct. The resultant fluidic forces exerted alternately on the diverters are sensed, and the sensor outputs are processed to generate a sinusoidal wave from which volumetric flow or mass flow output signals are derived.

Abstract: A magnetic flowmeter which includes a spool formed by a metallizable ceramic through which the fluid to be metered is conducted. The outer surface of the spool is metallized in its central region to define a pair of metering electrodes at diametrically-opposed positions, an electromagnetic field being established within the spool whereby when the flowing fluid intercepts this field, an emf is induced therein to produce a signal at the metering electrodes which is a function of flow rate. Overlying each metering electrode and projecting from the spool is a ceramic block whose outer surface is metallized to define a shield electrode which covers the metering electrode.

Abstract: A flangeless electromagnetic flowmeter unit interposable between the flanged ends of upstream and downstream line pipes for metering fluid passing through the line, the unit being encaged by bolts extending between the flanged pipe ends and being subjected to compression by these flanged ends to effect a fluid seal. The flowmeter is constituted by a non-magnetic spool of high strength to provide a flow conduit for the fluid. Surrounding the spool and concentric therewith is a cylindrical housing to define an annular inner chamber. Mounted at diametrically-opposed positions in the chamber along a coil axis normal to the longitudinal flow axis are electromagnetic coils, a strap joining these coils to define a magnetic circuit therewith. Electrodes are supported on the spool at diametrically-opposed positions along an electrode axis at right angles to the coil axis.

Abstract: An ultrasonic echo-ranging system adopted to measure the level of liquid in an open channel or other liquid container. The system includes an ultrasonic transducer disposed at a fixed position directly above the liquid surface, the nature of the gaseous environment therebetween determining the velocity of ultrasonic energy propagated therethrough. The transducer is excited to emit periodic pulses which are directed along a center path toward the liquid surface and reflected to produce liquid echo pulses which return to the transducer and are detected thereby. A reference reflector at a predetermined position relative to the transducer intercepts energy from a side path in the radiation pattern of the transducer to return it to the transducer to produce reference echo pulses. Means are provided to determine the transit time of pulses along the center path, and also to determine the transit time along the side path.

Abstract: An ultrasonic flowmeter for accurately measuring the flow rate of clean or dirty industrial process fluids passing through a pipe provided with upstream and downstream transducers. A transmission signal produced by a high-frequency generator acts to energize the transducers which are alternately excited at a relatively low switching rate whereby a beam emitted by the excited transducer is propagated through the fluid at an angle to the flow axis of the pipe and is intercepted by the other transducer to yield a received signal that is displaced in phase from the transmission signal to an extent depending on the transit time of the beam which reverses direction during each switching cycle. The received signals from the transducers are converted into a square wave that is compared to a wave derived from the transmission signal to produce a comparison output which is fed through a low-pass filter to exclude the high frequency content thereof.

Abstract: A driver for the excitation coil in the electromagnet of an electromagnetic flowmeter, wherein the fluid to be metered is conducted through a flow tube to intersect the transverse magnetic flux field created by the electromagnet. The driver includes an a-c line rectifier whose output is coupled to the coil by a pair of switching transistors, the control electrodes of which are connected to the output of a comparator having first and second input terminals. Applied to the first terminal of the comparator is an alternating square wave voltage, each cycle of which has a positive and a negative gating pulse such that the transistors are alternately actuated, the arrangement being such that the rectified output is applied by the transistors to the coil with a polarity which is alternately reversed.

Abstract: A vortex-shedding flowmeter for accurately measuring the flow rate of gases and liquid conducted through a flow tube provided with a dual-body shedder having a front section fixedly mounted across the tube, behind which is a pivotally mounted rear section separated from the front section by a gap configured to produce a fluidic feedback path so that a strong hydraulic interaction takes place between the sections and both actively contribute to the formation of periodic vortices which are alternately shed on either side of the shedder. The rear section is mounted on a pivot shaft extending along an axis normal to the flow axis of the tube, whereby the vortices which appear on either side of the rear section induce the rear section to oscillate. These oscillations are sensed to produce a signal representing the flow rate.

Abstract: A probe immersible in process water or wastewater having oxygen, chlorine or another gas dissolved therein and adapted to continuously and accurately measure the concentration of the gas. The probe includes a noble metal measuring electrode, an oxidizable metal counter-electrode and an electrolyte which in combination with the electrodes defines an electro-chemical cell whose output current depends on the amount of the gas passing into the cell through a diffusion membrane permeable to the gas being analyzed. In order to simulate the effect of rapid sample flow past the membrane and thereby maintain the analytical sensitivity of the instrument, the probe is vertically supported through a flexible coupling and includes an internal motor having an unbalanced rotor secured to its shaft. Rotation of the rotor causes the probe to nutate about its vertical axis to simulate the effect of a rapid sample flow.

Abstract: An auxiliary channel coupled to a selected loop in a plurality of process control loops included in a direct digital control system, the channel serving to expand the frequency response of the selected loop. The system is provided with a digital computer acting as an electronic controller common to all loops, each loop including a transducer sensing a particular process variable to produce a corresponding analog input signal which is digitized and compared in the computer with a set point signal to yield, after conversion, an analog output signal for operating a final control element in the loop to correct for process variations. The analog input signals from the respective loops are sequentially fed into the computer through a multiplexer at a relatively slow sampling rate whereby the loops are normally responsive only to the low-frequency component in the sampled process variables representing slow changes.

Abstract: An electrode wiring harness for an electromagnetic flowmeter which includes a non-magnetic metal spool having an insulating liner to define a flow conduit for the fluid to be metered, a pair of electrodes being mounted on the spool at diametrically-opposed positions along a transverse axis which is normal to the axis of the electromagnet assembly. The assembly is excited by a pulsatory wave to establish a magnetic field in the conduit that is intercepted by the fluid to induce a signal in the electrodes as a function of flow rate. The harness is constituted by a printed circuit board connected to the electrodes and disposed in a plane parallel to the electrode axis. The board has a conductive pattern thereon providing wiring from the electrodes to an external converter, the pattern including a loop coaxial with the electromagnet axis, whereby voltages induced therein by the magnetic field are balanced out.

Abstract: A compact electromagnetic flowmeter unit interposable between the flanged ends of upstream and downstream line pipes for metering fluid passing through the line, the unit being subject to compression by the flanged pipe ends to effect a fluid seal. The flowmeter is constituted by a non-magnetic metal spool of high strength whose inner surface is protectively covered by an insulating liner to provide a flow conduit for the fluid. Surrounding the spool and concentric therewith is a cylindrical housing fabricated of ferromagnetic material, the housing being formed by complementary half-pieces which include end plates that join the corresponding ends of the spool to define an annular inner chamber. Mounted adjacent the inner surface of the half-pieces at diametrically-opposed positions along a coil axis normal to the longitudinal flow axis are relatively thin coils which are shaped to conform to this surface to define electromagnets.