Abstract: In a method of testing open but not completely visible cavities (2), light beams (5) with defined intensities are directed into a standardized cavity (2). An intensity distribution of light beams (5) emanating from the standardized cavity (2) is recorded and saved as a standard distribution. The light beams (5) with the defined intensities are also directed into the cavities (2) to be tested. The intensity distributions of reflected light beams (5) emanating from the cavities (2) to be tested are recorded and compared with the standard distribution.

Abstract: In a method of measuring a mass flow distribution of a flow over a measuring plane (8), a light section (5) extending parallel to and around the measuring plane is formed, the light section having a small thickness (7). A picture is recorded, vertically to the measuring plane and during a defined interval of time t, of particles carried by the flow and passing through the light section. The distribution of the images of the particles (4) in the picture is evaluated for the mass flow distribution.

Abstract: A test device (1) serves for impinging a sample (2) with a high-energy gas jet (3). A plasma torch (4, 5) provides the gas jet (3) heated by a plasma and directed towards the sample (2). A massive metal plate (6) is positioned in front of the sample (2). The metal plate (6) forms the opposing electrode for the plasma torch (4-6). A drive system (7) is provided for rotating the metal plate (6) about an rotational axis (9). The metal plate (6) is provided with a gap (11) exposing the sample (2) to the gas jet (3) when the metal plate (6) is in a certain rotational position about the rotational axis (9).

Abstract: A method is provided for adjusting a laser doppler anemometer (1-5) having an emitting optic (3) which emits at least two laser beams (7, 8), and a receiving optic (4) for gathering light scattered by dispersed particles. The method comprises the steps of coupling a laser light (17) into an output of the receiving optic to make a focal point (12) of the receiving optic visible on a spaced reference surface (13); adjusting the receiving optic with respect to the surface so that the focal point of the receiving optic lies on the surface; and adjusting and regulating the emitting optic and the receiving optic with respect to each other so that a crossing point (11) of the laser beams coincides with the focal point of the receiving optic on the surface.

Abstract: In a method for determing the velocity of a flow seeded with particles reflecting light, the particles located in a light sheet (4) are illuminated with monochromatic light (5). The doppler-shifted frequency of the light reflected sideways out of the light sheet (4) by the particles is determined, and the velocity of the flow is determined from the doppler-shifted frequency. The un-shifted frequency of the monochromatic light with which the particles in the light sheet are illuminated is determined continously, and is used as a basis for the determination of the velocity of the flow from the doppler-shifted frequency.

Abstract: In the method, a volume (5) to be measured is illuminated by a pair of light beams (3) which cross each other. The Doppler-shifted scattered light (8) originating from the particles (6) which are moved along with the flow is registered and converted into electric signals (1). The Doppler frequency of the registered scattered light (8) is used as a measure of the flow velocity. The electric signals (1) of the registered scattered light (8) are digitized and represented in the form of an image and a coherent light beam is transmitted through the image. The coherent light beam (14) is focussed in a Fourier plane (18) as a result of which a Fourier-transformed image (22) of the electric signals (1), which exhibits a dot pattern (24), is generated. The Fourier-transformed image (20) is recorded and processed further.

Abstract: A method and device for contactless optical measurement of distance changes, in which two light beams (5, 6) are directed from a measuring table (1) through an optical system (9) in such a manner that they intersect on the surface of the object (11) and in the event of distance changes, the measuring table (1) is adjusted until a scattered light maximum is produced. The light beams (5, 6) exhibit a frequency displacement relative to one another, so that the scattered light which is produced is modulated; this can readily be separated from interfering light by means of amplifiers (15) which are selective in frequency, and in this manner an accurate determination of the scattered light maximum is made possible.

Abstract: A device for measuring pressures and variations of pressure with time at surface of test objects, for example wind tunnel models, is equipped with a plurality of pressure-sensitive sensors (4) arranged on a carrier (3). The pressure-sensitive sensors (4) are seated flush with the surface in the carrier (3) and this, in turn, is arranged flush with the surface of the test object at the test location. In the carrier (3) an operational amplifier is provided for each sensor (4). The underside of each sensor (4) is connected via as short a line (10) as possible to the associated operational amplifier. At the carrier (3), connections (7, 11) for supplying the operational amplifiers (18) and for conducting the output signals are provided. All top sides of the sensors (4) are connected to each other and to a combined ground connection (5) of the operational amplifiers thru an electrically conductive coating.