Abstract: An apparatus for gauging the level of a liquid, above which a gas having a dielectric constant within a predetermined dielectric constant range exists, comprises a transmitter for transmitting a microwave signal in a propagation mode in a tube through the gas towards the liquid surface; a receiver for receiving the microwave signal reflected against the liquid surface and propagating back through the tube; and a processing device for calculating from the propagation time of the transmitted and reflected microwave signal the level of the liquid. In order to essentially avoid the influence on the calculated level by the dielectric constant of the gas above the liquid, the transmitter is adapted to transmit the microwave signal in a frequency band, at which the group velocity of the microwave signal in the propagation mode in the tube is, within the predetermined dielectric constant range, essentially independent of the dielectric constant.

Abstract: An apparatus for gauging the level of a liquid, above which a gas having a dielectric constant within a predetermined dielectric constant range exists, comprises a transmitter for transmitting a microwave signal in a propagation mode in a tube through the gas towards the liquid surface; a receiver for receiving the microwave signal reflected against the liquid surface and propagating back through the tube; and a processing device for calculating from the propagation time of the transmitted and reflected microwave signal the level of the liquid. In order to essentially avoid the influence on the calculated level by the dielectric constant of the gas above the liquid, the transmitter is adapted to transmit the microwave signal in a frequency band, at which the group velocity of the microwave signal in the propagation mode in the tube is, within the predetermined dielectric constant range, essentially independent of the dielectric constant.

Abstract: A device for gauging the level of a fluid in a container includes a floating roof, a transmitter for feeding a first microwave signal downwards in the direction of a fluid surface of the fluid, and a receiver for receiving a reflected microwave signal. The device includes a collector located above and in the vicinity of the floating roof, collecting the first microwave signal producing a collected microwave signal. The device also includes a vertical wave guide passing through the floating roof. The vertical wave guide guides the collected microwave signal to the fluid surface, and receives a reflected microwave signal reflected from the fluid surface. The vertical wave guide then guides the reflected microwave signal back to the collector and further to the receiver. It is a special feature to permit accurate measurement of the level of the fluid surface without having direct access to the surface.

Abstract: A device for gauging the level of a fluid in a container is described. It comprises a transmitter for transmitting a polarizable microwave signal through a first waveguide section, a receiver for receiving a reflected microwave signal, an electronic unit for determining the reflex position of the reflected microwave signal and an antenna means with a second waveguide section. The device is primarily characterized in that the transmitter and receiver, respectively, transmits and receives a waveguide mode each, mutually orthogonal, and by an easily replaceable third waveguide section (6, 16, 17) inserted between the first (2) and second (5) waveguide sections, provided with means (12, 14, 15, 22) for polarization and/or damping for optimal adaptation of the device to various containers and antennae.

Abstract: A device in storage tanks with a floating roof and a vertical stillpipe with a number of openings distributed along the length of the same for reducing the outflow of volatile substances from stored products is described. The device comprises a floating body with at least one peripheral seal engaging the inner circumference of the stillpipe. The volume/weight relationship of the floating body is such that it floats in the product and encloses the product surface within its periphery. The floating body is designed so that the gas pressure inside the body is the same as the gas pressure within the stillpipe above the floating body. The body is so constructed that direct gauging with microwaves may be performed against the product surface through the inside of said stillpipe.

Abstract: A device for gauging the level of a fluid in a container with a microwave signal is described. The device comprises a vertical tube (1) mounted in the container, and a transmitter and a receiver and an electronic unit for determining the level based on the reflex position of the microwave signal. The device is characterized particularly by a calibration device in the form of a polarization means (6, 7) for polarizing the microwave signal in two polarization planes separated from each other and at least one reflecting reactance (10) in the tube (1) arranged to give a substantially stronger reflex of the microwave signal in the first polarization plane than in the second.

Abstract: A device for gauging the level of a fluid in a container having a gas above the surface of the fluid. The device comprises a microwave transmitter transmitting a microwave radio signal through the gas to the surface and a receiver for receiving the microwave signal reflected by the surface. An electronic unit is arranged to calculate from the propagation time of the microwave signal a first distance from the transmitter to the surface of the fluid and thereby the level in the container. The microwave signal is preferably within the radar frequency range. A sound transmitter is also provided for transmitting a sound signal through the gas to the surface of the fluid and is capable of receiving a sound signal reflected from the surface of the fluid. A means is provided for correcting the first distance to a second corrected distance as a function of the microwave velocity and the known relation between the sound velocity and the microwave velocity.

Abstract: The invention concerns a method and an apparatus for measuring the level of a material with microwave signals. The apparatus consists of a signal processing unit (10) and a transmitter unit (1) of known type. The transmitter unit produces a measuring signal having a frequency (f.sub.m) corresponding to the distance (H) to be measured and a reference signal having a frequency (f.sub.r) corresponding to an accurately known length (L). In the signal processing unit (10) the reference signal is multiplied by a selectable number (AQ) which is proportional to the quotient of an assumed value for the distance divided by the known length (L), after which the frequency is divided by a fixed number (Z) so that the frequency of the signal after multiplication and division becomes equal to the expected frequency of the measuring signal.

Abstract: In a method of measuring the level of a flowing material kept in a container there is employed a microwave signal that is fed from a transmitter through a tubular waveguide (7) that extends vertically downwardly through the container and communicates therewith so that the surface (10) of the material in the waveguide follows the level of the surrounding material. The signal is reflected from the surface back up through the waveguide and is conducted to a receiver to be employed, after signal processing in an electronic unit, for determining the level of material in the container. The microwave signal is fed to the waveguide by way of a mode generator (11) that produces only one dominant propagation mode of the signal, the wavelength of which is smaller than the diameter of the waveguide (7).