Abstract: The invention relates to a method for improving the selectivity of a polymer film gas sensor. According to the method, the gas sensor is heated and a sensor parameter sensitive to the variable under measurement is recorded. According to the invention, the parameter of the sensor sensitive to the variable under measurement is measured at a plurality of instants during both the heating period and the cooling period of the sensor, a hysteresis function of the sensor response is formed over the heating and cooling periods, and on the basis of the hysteresis function, the concentration of each measured gas component is determined.

Abstract: The invention relates to a method and temperature sensor structure for compensating radiation error particularly in a radiosonde, rocket sonde or dropsonde. According to the method, each sonde carries at least one temperature sensor. According to the invention, the temperature measurement is carried out by means of two temperature sensors, both having low emissivities but different absorption coefficients for solar radiation.

Abstract: The invention relates to an apparatus and method for measuring visibility and present weather. The apparatus includes a light source (1) for directing a light ray toward the object (9) to be measured, a detector (3) for measurement of light which is forward scattered from the object (9), and computing elements (12-15) adapted to differentiate the signal representing the forward scattered light from signals representing stray or ambient light. The apparatus may include a pulsed light source, a receiver (19) for receiving directly backward reflected/scattered light pulses, and computing elements (11) for computing the propagation delays of the different backward reflected components in the received pulse-shaped optical signal.

Abstract: A method and apparatus for calibrating an NDIR gas analyzer is provided. According to the method, the apparatus under calibration is calibrated with the help of a reference apparatus under controlled conditions. The reference apparatus is a laboratory-calibrated NDIR measurement apparatus in an arrangement based on circulating ambient air via both a measurement chamber of the measurement apparatus under calibration and measurement chamber of the laboratory-calibrated measurement apparatus. Adjusting the reading of a display, or alternatively, an output signal of the measurement apparatus under calibration to be equal to the reading of the display, or the output signal, respectively, of the reference apparatus is performed by a control device of the measurement apparatus.

Abstract: A method of controlling a short-etalon Fabry-Perot interferometer used in an NDIR measurement apparatus includes generating a measurement signal using a radiant source. The measurement signal is provided to a sample point containing a gas mixture to be measured. The measurement signal is bandpass-filtered with an electrically tuneable Fabry-Perot interferometer using at least two wavelengths of the interferometer passband. The measurement signal is passed via an optical filter component prior to detection, and the filtered measurement signal is detected by a detector. During the measurement cycle, the passband frequency of the interferometer is controlled to coincide at least partially with the cutoff wavelength range of the optical filter component.

Abstract: The invention is related to an electrically modulatable thermal radiant source with a multilayer structure. The radiant source includes a substrate, a first insulating layer formed onto the substrate, a radiant surface layer formed onto the first insulating layer, a second insulating layer formed on the radiant surface layer, a first metallization (incandescent filament) layer formed on the second insulating layer, a third insulating layer formed on the first metallization layer, and a second metallization layer for contacting formed on the third insulating layer. According to the invention, very thin incandescent filaments are formed from the first metallization layer and surrounded by the other elements of the multilayer structure as a uniform, planar plate.

Abstract: The invention relates to a method and an apparatus for codeless GPS positioning. According to the method, the unit (2) to be positioned receives GPS signals from several satellites (4), the codes of the GPS signals are removed, and the extracted carrier signals are transmitted out from the unit (2) to be positioned for the purpose of determining the position and/or velocity of said unit (2) to be positioned. According to the invention, the carrier signal frequencies are detected by means of a phase-locked loop and the thus detected signals are transmitted in digital format out from the unit (2) to be positioned for the purpose of further processing.

Abstract: A miniaturized spectrometer for gas concentration measurement includes a radiation source for admitting electromagnetic radiation onto the gas to be measured, a detector for detecting the radiation transmitted through or emitted from the gas, an electrically tunable Fabry-Perot interferometer placed in the path of the radiation prior to the detector, control electronics circuitry for controlling the radiation source, the interferometer and the detector. The radiation source, the detector, the interferometer and the control electronics are integrated in a miniaturized fashion onto a common, planar substrate and the radiation source is an electrically modulatable micromechanically manufactured thermal radiation emitter.

Abstract: The present invention relates to a method and apparatus for measuring road surface conditions. In the method of measuring road surface conditions, the conditions prevailing on the surface of a road are measured by a sensor head mounted in the pavement of the road with the top surface of the sensor head aligned substantially flush with the pavement of the road. According to the invention, an optical signal is impinged from below the road to the top surface of the road, the reflection/backscatter of the optical signal is measured inside the pavement layer of the road, and weather/driving conditions prevailing on the road top surface are determined from the reflected and backscattered signal values.

Abstract: The invention relates to a method and apparatus for linearizing a flow velocity sensor based on pressure difference measurement. According to the method, a difference of two pressure signals is measured from the flow under measurement and is proportional to the square of the flow velocity. The pressure difference is measured using a micromechanically manufactured symmetrical capacitive differential pressure sensor based on the force balance principle. The pressure-induced deviation from force balance is compensated for by inducing on the pressure-sensing diaphragm of the differential pressure sensor a force-balance-restoring electrostatic pressure. The amplitude of the force-balance-restoring electrical feedback control signal also acts as the system output signal and is directly proportional to the square root of the difference of the two pressure signals, and thus, a linear function of the flow velocity.

Abstract: The invention concerns an electrical impedance detector for measurement of physical quantities, in particular of temperature or humidity, as well as a process for manufacture of the detectors. The impedance detector is composed of pieces cut off from a continuous detector filament (20). The detector filament (20) comprises an electrically conductive pair of electrode wires (10a,10b) or an equivalent assembly of electrode wires, on/between which there is an active material (11) whose impedance properties are a function of the physical quantity to be measured. The different electrode wires (10a,10b) of the detector filament (20) in the pieces of detector filament (20) have been cut off at different points (41a,41b), compared with one another, so that the impedance (CM) to be measured will be formed in the area (CV) between the cut-off points (41a,41b) of the electrode wires (10a,10b).

Abstract: The invention is related to a symmetrical capacitive differential pressure sensor formed by depositing onto a substrate (1) using the surface-micromachining methods of semiconductor device manufacturing technology. The sensor comprises the following, entirely from each other electrically insulated thin-film layers: an at least partially conducting sensing diaphragm (5) made from polysilicon and conducting counterelectrodes (3 and 7) adapted to both sides of the sensing diaphragm (5). According to the invention, said counter-electrodes (3 and 7) are made from polysilicon thin film and comprise at least one electrically conducting area.

Abstract: A capacitive pressure transducer structure and a method for manufacturing the same comprises a transducer structure having a contiguous diaphragm structure (2), which at least in some parts is conducting to the end of forming a first electrode (4) of a transducing capacitor, a substrate (3) which is permanently bonded to a first surface of the diaphragm structure (2) and comprises a second electrode (5) of the transducing capacitor, spaced at a distance from and aligned essentially at the first electrode (4), and a silicon structure (1), which is permanently bonded to a second surface of the diaphragm structure (2), incorporating a space (21) suited to accommodate the deflection of the first electrode (4). The angle .alpha. formed between vertical walls (11) of the space (21) and the first electrode (4) is smaller than or equal to 90.degree., and the material surrounding the space (21) is silicon or doped silicon.

Abstract: A single-channel gas concentration measurement method and apparatus. According to the method, a radiant source is employed to generate a measuring signal, the measuring signal is subsequently directed to a measurement object containing a gas mixture to be measured, the measuring signal is subsequently bandpass filtered using at least two passband wavelengths, and the filtered measuring signals are detected by a detector. According to the invention, the bandpass filtering step is implemented by a single electrostatically tunable, short-resonator Fabry-Perot interferometer.

Abstract: The invention relates to an indirect measurement method of dewpoint or gas concentration and an apparatus suited for prediction of icing. The method is based on measuring the relative concentration of the gas directly and simultaneously measuring the temperature of the element (3) measuring the relative concentration of the gas. According to the invention, the temperature of the relative value measuring element (3) is shifted so as to bring the operation of the measuring element to a measurement range of maximally high sensitivity.

Abstract: An electrically modulatable radiant source includes an essentially planar substrate, a well or hole formed in the substrate, and at least one incandescent filament attached to the substrate. The incandescent filament is aligned with the well or hole and is formed of a metallic compound which readily oxidizes at an operating temperature of the incandescent filament. An oxidation resistant film encapsulates the incandescent filament to prevent the filament from oxidizing. Furthermore, contact pads are formed on the substrate at both ends of the incandescent filament for feeding electric current to the incandescent filament.

Abstract: The invention is related to a feedback method and apparatus for a capacitive differential pressure transducer. According to the method, a pressure-transducing conducting diaphragm (1) forming a first, moving electrode of the transducer capacitances is kept in a force balance state by means of a pulse train signal applied to a fixed electrode (2, 3). According to the invention, the diaphragm (1) is kept stationary in a geometrically constant state and a desired electric potential is applied to the diaphragm (1), the pulse train signal is applied to at least two of the fixed electrodes (2, 3), or alternatively, sets of fixed subelectrodes. The signals applied to separate electrodes (2, 3) or sets of subelectrodes are at opposite polarities referenced to the electric potential of the pressure-transducing diaphragm (1) for at least a portion of the measurement duration, and are of equal amplitude at least for each pair of electrodes (2, 3).

Abstract: Electrical impedance detector for measurement of physical quantifies, in particular of temperature or humidity. The detector comprises conductor electrodes (10a, 10b; 10A,10W), between which the electrical impedance (C.sub.M) that represents the physical quantity to be measured is measured. Between the conductor electrodes (10a, 10b;10A, 10W) there is an active material (11;11P) whose impedance properties are a function of the physical quantity to be measured. The detector is composed of pieces cut-off out of a continuous detector filament (20; 20H;20K), which detector filament (20;20H;20K) comprises a conductive electrode wire or an assembly of electrode wires (10a, 10b; 10A, 10W), on/between which there is an active material (11;11P) whose impedance properties are a function of the physical quantity to be measured. Further, a novel process is described for the manufacture of said detectors.

Abstract: The invention relates to a method and sensor structure for measuring the concentration of nonpolar gases such as carbon dioxide. According to the method, the concentration of the nonpolar gas adsorbed/absorbed in a polymer film (2) is determined by detecting the weight of the polymer film (2). According to the invention, the dielectric coefficient of the polymer film (2) is measured, and on the basis of this, a correction is made in the concentration measurement result obtained from the weight measurement. (FIG.

Abstract: Detector and method for detecting the presence of a liquid, such as water dew or of ice, or for detecting a change of phase in liquid, based on a change in an electrical resistance. The detector comprises a substrate onto whose face one or several resistor patterns are applied. For detecting the presence of a liquid or ice or equivalent by a change in the detector resistance, a low-mass detector resistor pattern is applied onto a substrate out of such a metal or equivalent as has a considerable dependence on temperature. On the substrate, there are contact patterns that feed a short pulse of electric current to heat the detector resistor as a short pulse, the presence of a liquid or ice and or a change of phase being detected by the change in resistance taking place during the short pulse. The thickness of the metal film in the resistor pattern (15) of the detector resistor (R.sub.det) is, as a rule, chosen as s<1 .mu.m.