Abstract: An ultrasonic, echo-ranging instrument for measuring liquid level, the instrument including a transducer dispoed at a fixed position directly above the liquid surface. The transducer is excited to emit periodic pulses which are intercepted by the liquid surface as well as 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. 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: An ultrasonic echo-ranging meter for measuring the changing level of liquid in a tank or open channel, the meter including a transducer at a raised position above the liquid surface. Pulses of ultrasonic energy transmitted by the transducer are directed toward the liquid surface and reflected thereby to produce main echo pulses that are picked up by the same transducer. The round trip transmit time of the pulse energy in the gaseous medium above the liquid depends on the distance between the transducer and the liquid surface, this time being measured to provide a reading of liquid level. Also intercepted by the transducer are parasitic echo pulses originating from reflecting wall surfaces and other obstacles in the vicinity of the tank or channel, which parasitic pulses may be confused with the main echo pulses and result in an erroneous reading.

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: 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 including a pair of alternately-excited upstream and downstream transducers, an acoustic pulse emitted by one transducer and propagated through the fluid being received by the other. The time delay difference between the upstream and downstream transit times is measured to determine the flow rate of the fluid. A single pulse power generating device is employed to excite both transducers, the device being coupled to the transducers through respective gates, each activated by an associated gate driver. Also included are logic means to periodically activate the device to produce power pulses and to alternately activate the gate drivers to cause the pulses to pass through alternate gates to excite one transducer and then the other.

Abstract: An ultrasonic flowmeter for measuring the flow rate of fluid conducted through a pipe, the meter including a pair of alternately-excited transducers, one being placed at an upstream and the other at a downstream pipe position. An acoustic pulse transmitted by one transducer and propagated through the fluid at an angle to the longitudinal flow axis is received by the other transducer. The time delay difference between the upstream and downstream transit times which depends on flow velocity is determined to provide a flow rate reading. Since the geometry of the pipe is a major factor in flow rate measurement, to factor-in this geometry, a third transducer or one of the pair is arranged to produce an auxiliary acoustic pulse that is propagated in a direction normal to the flow axis to produce a first echo at the interface of the inner pipe surface and the fluid on the transducer side, and to produce a second echo at the diametrically opposed side of the pipe, these echoes being received by the same transducer.