Abstract: A method and an apparatus for measuring dewpoint of different kinds of gases is based upon cooling the measured gas by mixing it with a cold gas down to the dewpoint and then detecting the generated mist by optical sensors. The cooling gas is routed to a measurement area (7) from outside the process and the cooling gas is brought to an appropriate temperature below the dewpoint of the measured gas before being conducted to the measurement area (7) where it is mixed with the measured gas. Mist generated during the cooling of the measured gas is detected by illuminating the measurement area (7) by a light emitting source (8) and measuring the light (2) scattered from the mist or light (3) penetrating through the mist with the help of a photodetector (9).

Abstract: The invention concerns a capacitive humidity sensor (6) capable of being connected to a measurement device of dielectric factor and a method for producing the sensor. The sensor comprises a dielectric layer (3), whose dielectric factor changes according to the moisture content absorbed in the layer, and at least two galvanically isolated conductive layers (2,1) enclosing the dielectric layer (3), where one of the conductive layers (2) of the capacitor construction is provided with a random pattern of clefts (7), which allow an immediate communication of ambient air with the dielectric layer (3). According to the invention, the dielectric layer (3) has a solid structure without cracks corresponding to the clefts (7) of the conductive layer (2). The construction according to the invention offers a reduction of the capillary effect and associated hysteresis up to a complete elimination of the effect in some embodiments of the invention.

Abstract: A method for measuring the velocity (v) of a moving target (A). Radio signals are transmitted by means of radio transmitter-receiver arrangements of both the measuring station (B) and the target station (A) and received at the opposite stations (A,B), the frequencies of which signal include Doppler shifts (fd) to be observed both at the measuring station (B) and in the measuring target (A). On the basis of the Doppler shifts (fd), the escape and/or approach velocity (v) of the target to be measured is determined relative to the measuring station (B). Radio signals are transmitted from the measuring station (B) and the target station (A), the frequencies of which signals deviate from each other by a relatively small frequency difference (fk) or by a Doppler frequency shift (fd), the absolute value of which small frequency difference remains at least as high as the absolute value of the largest expectable Doppler frequency shift (fd.sub.max).

Abstract: The present invention concerns an apparatus and method for measuring the azimuth and elevation of an object. The apparatus includes a platform; a base plate arranged to the construction of the platform rotatably in a plane, which is essentially horizontal; a sensor frame attached to the base plate; at least three sensor elements attached to the sensor frame; and an electronics unit for the control of the sensor elements, capable of performing the processing of signals received by the sensors. The sensor frame is rigidly attached to the base plate and the directional pattern of the sensor elements is such as to cover the entire angle span of interest in the elevation plane, while the pattern covers an essentially narrower angle in the azimuth plane. The direction finder does not easily lose the tracked object performing movements particularly in the elevation plane.

Abstract: This invention concerns a calibration method and compatible sensor construction for the determination of relative concentration of a gas or vapor. According to the method a sensor is brought to controlled conditions, in which at least one calibration point is determined, and then with the help of the calibration point measurement values the response of the sensor for the measured gas or vapor is computed. According to the invention, both the temperature of the sensor and the relative concentration of the desired gas or vapor is measured at the actual measurement site, and the temperature of the sensor is deviated from the ambient temperature so transiently that the partial pressure of the measured gas or vapor can be assumed to stay at least approximately constant at the measurement site, whereby the results of measurements performed at each deviated temperature level can be used for computing a correction factor for the calibration of the sensor.

Abstract: Method and device in the antenna and receiving system of a radio theodolite, wherein the radio signal arriving from the transmitter of the object (31) to be measured is received by means of at least three antennas (1 . . . n-1) in the antenna field (AK) as well as by means of a reference antenna (n). The signals received from said antennas are passed to the receiving system, being controlled and selected by an antenna-selection switch (10a). By means of said system, the phase differences between the signals of different antennas are detected and measured, on the basis of which phase differences it is possible to calculate the angles of incidence (.alpha.,.epsilon.) of the signals on the basis of the known coordinates of location of the antennas in the antenna field (AK). In the method an outer reference antenna (n+1) is used which does not belong to the antenna field (AK) proper. The phases of the antennas (1 . . .

Abstract: The invention concerns a sensor construction for, e.g., the measurement of gas concentration, including a sensor element; a heating element arranged in conjunction with the sensor, with which the sensor element can be brought to a temperature above the ambient gas atmosphere temperature; and an electronics circuitry section, with which the desired electrical properties of the sensor element can be measured and the heating element of the sensor can be controlled. According to the invention, the sensor element and the electronics circuitry are placed onto the same planar substrate, and the substrate is processed to have adjacent openings around the sensor element area to the immediate vicinity of the area so that the openings extend through the substrate whereby the sensor area is connected to the surrounding part of the substrate and, then, to the electronics circuitry section, only along thin isthmuses remaining between the openings.

Abstract: A pressure transducer comprises a sensor (16), an electronic circuitry part (17), a pressure connection (13), and an electrical connection (14). According to the invention, the transducer is constructed as a plug-in unit (5) and both the pressure connection and the electrical connection (14) are designed integral with the socket (6). The plug-in unit (5) may incorporate a splash-water protection (8) with a latch mechanism (9) for locking the plug-in unit (5) and the socket (6).

Abstract: This invention concerns a method for trimming a planar capacitor. According to the method, a laser emission is focused to an electrode of a capacitor formed on a substrate transparent to laser emission and including of an upper electrode, an insulation layer, and a lower electrode, in order to achieve a passivation effect on the electrode. The laser emission is focused according to the invention locally onto the lower electrode through the substrate in order to achieve a heating effect on the lower electrode, thereby oxidizing the electrode material so that the lower electrode is locally converted into an electrically nonconductive state while being protected by the substrate and the insulation layer. The trimming method in accordance with the invention is accurate and offers a stable capacitance value.

Abstract: This invention concerns a capacitive pressure sensor construction and method for fabricating said sensor. The pressure sensor construction comprises a base part (1, 2, 4), comprising an electrically conductive silicon layer (1, 2) and a thereupon permanently bonded planar intermediate layer (4) of an insulating material with an essentially smaller thickness than that of the silicon layer (1, 2); a fixed planar capacitor electrode (9) fabricated on the base part (1, 2, 4); and a deflecting membranous capacitor electrode (6) fabricated of silicon and integral with a surrounding, essentially thicker base element (5), and gappedly spaced from and aligned at least approximately coincident with the fixed capacitor electrode (9), so that a hermetically sealed chamber (25) remains between the fixed electrode (9) and the membranous electrode (6).

Abstract: A capacitive pressure transducer includes a capacitive sensor structure, a case into which the capacitive sensor structure is adapted, channels formed in the case for introducing a measured medium into the capacitive sensor structure, and electrical conductors to make the pressure-related capacitive sensor information externally available. According to the invention, the capacitive sensor structure is fixed to the case by means of elastic structures, which elastic structures provide a floating support for the capacitive sensor structure adapted between the elastic structures. The construction in accordance with the invention cancels errors caused by temperature variations.

Abstract: A third reference capacitor cooperates with first and second reference capacitors to minimize measurement errors in a measurement circuit of the type in which reference and measurement capacitors are connected, one at a time, to an oscillator of the measurement circuit to generate an output frequency proportional to the capacitance of the capacitor being measured. The measurement errors introduced by different temperature and loading conditions during calibration and measurement modes of the measurement circuit are minimized.

Abstract: This publication discloses a capacitor construction for use in pressure transducers, including a substrate plate having of a silicon wafer and a thinner glass wafer. A first fixed capacitor plate is provided for overlying the substrate plate plate. A silicon plate is adapted to encircle the substrate plate with its thinned center area acting as a moving capacitor plate by virtue of its diaphragm behavior and a top plate overlying the silicon plate includes a silicon wafer and a glass wafer bonded to the silicon wafer and having a thickness essentially smaller than that of the silicon wafer. According to the invention, over the supporting substrate plate and between the first capacitor plate and its encircling silicon plate, is provided another overlying capacitor overlying plate, which essentially encloses the first capacitor plate. With this design, a reduced temperature sensitivity is accomplished in the capacitor construction.

Abstract: Measurement equipment based on the measurement of light transmission are plagued by changing characteristics of protective glass surfaces due to contamination or other factors. In a method, light transmission is measured by sending light from a transmitter (1) and recording the received light intensity at a receiver (2), after which the light intensity is obtained by computation means. Light from light sources (5, 6) travels into protective glasses (3, 4) of the transmitter and the receiver so that the light rays are subjected to total internal reflection within the glasses, after which the intensities of the totally reflected light rays are measured by a detector (7, 8), and the obtained intensity values are used for correcting the intensity attenuation, effected by the protective glasses and their contamination onto the path from the transmitter to the receiver.

Abstract: Method of and arrangement for measuring low capacitances include generating a periodic frequency signal having time periods of duration dependent on capacitance, and alternately connecting an unknown capacitance to be measured and a known reference capacitance, one after the other, to a frequency generator for an equal number of time periods of the frequency signal. Each time period has a first and a second time interval proportional to the reference capacitance and the unknown capacitance, respectively. A DC voltage output signal proportional to the unknown capacitance being measured is generated in response to the durations of the first and second time intervals. The DC voltage output signal is preferably scaled, linearized and temperature compensated.

Abstract: A method of and arrangement for measuring impedances, particularly low capacitances, by alternately connecting one or more reference impedances and sensor impedances to a measuring circuit. A programmed memory is used to take into account the individual non-linearities of the impedance sensor(s) and, optionally, to compensate variations of ambient circumstances such as temperature.

Abstract: A method and an apparatus for determining the covering on a road surface. A measurement signal is fed into a pair of electrodes inlaid in the road surface and acting as a detector (5), whereby the ratio of the measurement current to the voltage formed across the detector (5) is determined in order to establish the conductivity of the covering on the road surface. The signal fed into the detector (5) is a low-voltage and low-frequency symmetric alternating voltage signal, and the electric polarization between the poles, caused by the measurement current, is measured in order to determine the thickness of the covering on the road surface.

Abstract: A capacitive detector for absolute pressure, which comprises a base and a stationary capacitor plate (7) attached onto the base (3). An aneroid capsule (4) is arranged in connection with the base (3) and provided with a mobile capacitor plate area (5, 6) directed towards the base (3) and changing its distance from the stationary capacitor plate (7) by the effect of pressure. A silicon plate (2) is attached onto the base and has membrane-like middle portion (5, 6) acting as a mobile capacitor plate. A plate structure (1) is attached hermetically onto the silicon plate (2) such that the space of the aneroid capsule (4) is located between the plate structure (1) and the silicon plate (2).

Abstract: Described herein is a capacitive absolute pressure transducer including a flat base plate (9) of insulating material, e.g., of glass, with a fixed capacitor electrode (10), aligned on the base plate. A silicon-material moving diaphragm electrode (5) of the capacitor is at least partly aligned with the fixed electrode (10), properly spaced to implement a hermetically sealed vacuum chamber (7) between the fixed electrode (10) and moving diaphragm electrode (5). Electrical contacts (12) are attached to the fixed electrode (10) and the moving diaphragm electrode (5). According to the invention, the flat base plate (9) is bonded to an electrically conductive wafer (8) to implement a laminated substrate (2), the diaphragm electrode (5) fabricated integral with a surrounding and essentially thicker collar part (18), and the electrical contact to the fixed capacitor plate (10) in the area of the vacuum chamber (7) is a well (11, 12) extending through the base plate (9) to the wafer (8).