Abstract: The invention relates to a method for determining the non-volatile component of aerosol particles in a gas sample, especially in the exhaust gas of internal combustion engines, where the aerosol particles are deposited on an oscillating sensor (2) of at least one crystal microbalance (3), and the change in at least one oscillation parameter of the oscillating sensor is employed as measurement variable. According to the invention the oscillating sensor (2) of at least one crystal microbalance (3) is maintained at a temperature of more than 200° C. during deposition of the aerosol particles, and preferably between 250° C. and 350° C.

Abstract: A process to determine aerosol particles in gaseous samples, specifically in the exhaust of diesel motors, includes the at least indirect deposit of aerosol particles on a piezoelectric oscillating crystal and the determination of the oscillation parameters of the piezoelectrically stimulated oscillation of the crystal. In order to assure the required reproducibility reliably and independently of the type of aerosol particles, and thus to achieve a high quality of measurements, the piezoelectric crystal is charged to oscillation during less than half the period of deposit of aerosol particles.

Abstract: The invention relates to a method for determining the non-volatile component of aerosol particles in a gas sample, especially in the exhaust gas of internal combustion engines, where the aerosol particles are deposited on an oscillating sensor (2) of at least one crystal microbalance (3), and the change in at least one oscillation parameter of the oscillating sensor is employed as measurement variable. According to the invention the oscillating sensor (2) of at least one crystal microbalance (3) is maintained at a temperature of more than 200° C. during deposition of the aerosol particles, and preferably between 250° C. and 350° C.

Abstract: The invention relates to a piezoelectric single crystal element which is provided with electrodes on at least one face or on opposing faces and is excitable to produce a thickness shear vibration. In accordance with the invention the single crystal element has a crystal cut with a fundamental resonance frequency excitable in the thickness shear mode, in which the effective electromechanical coupling factor keff is between 0.05% and 3%, and preferably, between 0.1% and 2%. This allows resonators with a high quality factor to be produced.

Abstract: A process to determine aerosol particles in gaseous samples, specifically in the exhaust of diesel motors, includes the at least indirect deposit of aerosol particles on a piezoelectric oscillating crystal and the determination of the oscillation parameters of the piezoelectrically stimulated oscillation of the crystal. In order to assure the required reproducibility reliably and independently of the type of aerosol particles, and thus to achieve a high quality of measurements, the piezoelectric crystal is charged to oscillation during less than half the period of deposit of aerosol particles.

Abstract: To improve temperature compensation of a piezoelectric element measuring mechanical variables, such as pressure, force, and acceleration, with two or more piezoelectric crystal elements, at least one of the crystal elements differ from the other crystal element(s) either physically or chemically, the positive temperature coefficient of a piezo-coefficient of at least one piezoelectric crystal element compensating the negative temperature coefficient of the other crystal element(s), so that the overall piezoelectric sensitivity of the measuring element will remain essentially constant within a given temperature interval.

Abstract: A piezoelectric crystal element for surface acoustic wave applications with a quartz substrate with at least one substantially planar quartz surface, the planar quartz surface having an epitaxially grown layer of a quartz-isomorphous crystal with the total molecular formula ABO.sub.4, A standing for Al or Ga, and B for P or As, and the quartz surface and the epitaxial layer having approximately the same crystallographic orientation.

Abstract: In order to obtain large, high-quality crystals or crystal layers of a me orthophosphate, in particular, GaPO.sub.4 or AlPO.sub.4, from a nutrient solution with the use of a seed plate, the proposal is put forward that in the initial phase of the growth process a seed plate of alpha-quartz (.alpha.-SiO.sub.2) be introduced into the nutrient solution, and that fluoride ions (F.sup.-) be added to this solution, at least for formation of the primary crystal layer on the quartz seed plate.

Abstract: For surface acoustic wave devices temperature-compensated piezoelectric crystal elements with one or more planar faces are used. An improvement in temperature stability may be expected if the crystal element is made from GaPO.sub.4 and the planar face is defined by Euler angles .lambda. in the range of 0.degree., .mu. in the range of 40.degree. to 75.degree., i.e. preferably 50.degree. to 60.degree., and .theta. in the range of 0.degree..

Abstract: A sensor containing at least one piezoelectric transducer element is operated via a common, single signal line in both possible operating modes--first, at low frequencies as a measuring element for a mechanical quantity upon utilization of the direct piezoeffect and, second, at higher frequencies as a piezoelectric resonator upon utilization of the inverse piezoeffect for electrical excitation of mechanical oscillations and of the direct piezoeffect for generating the piezoelectric reaction. A high-frequency signal (u.sup.HF, u.sub.F) that describes the resonant characteristic and a lower-frequency signal (u.sub.NF, u.sub.Q) that describes the mechanical influence are generated from the measured signal on the signal line. The faultless function of the sensor together with the appertaining measuring amplifier, for example, can thus be monitored immediately during a measurement with the sensor or a simultaneous measurement of two different quantities can be undertaken.

Abstract: In order to prevent crystal seeds with retrograde solubility from dissolving in the hydrothermal growing solution at the beginning of the growing process, and to protect the finished crystal at the end of the growing process, and in order to reach the thermodynamic growth equilibrium as soon as possible, the proposal is put forward that the growing solution be prepared, pre-saturated and pre-heated to a temperature close to saturation temperature outside of the growing tank, and that, for the growing process proper, the hot growing solution be added to the pre-heated growing tank provided with crystal seeds, where it should be further heated to a temperature at which the crystals start growing, and, further, that the hot growing solution be quickly removed from the growing tank as soon as the growing process has been completed.

Abstract: A charge amplifier circuit comprising an operational amplifier unit whose signal output is back to a signal input of the amplifier unit via a capacitative feedback element, the signal output of the operational amplifier unit also being coupled to an input of a following, further transmission unit that has a proportional, integrating transfer characteristic with a break-over frequency that is at least approximately equal to the break-over frequency of the operational amplifier unit, this being at least in the proximity of the break-over frequency defined by the feedback element of the operational amplifier unit. The feedback element of the operational amplifier unit can be optimized independently of the operating frequency range, this, allowing for a low resistance value for the feedback element given a transfer behavior that remains linear, this despite the low capacitor value that increases the charge sensitivity.

Abstract: In order to improve the temperature stability of piezoelectric and elastic properties of piezoelectric crystal elements based on GaPO.sub.4, preferably for resonator applications, and to facilitate alignment when the crystal elements are cut from the raw crystal bars, the proposal is put forward that the principal plane H of the crystal element be parallel to a cutting plane, which is generated by rotating a hexagonal prism face of a raw crystal bar, which lies parallel to the optical axis, around one of the two-fold crystallographic symmetry axes a.sub.1, a.sub.2 or a.sub.3 through an angle .theta. of -5.degree. to -22.degree..

Abstract: A method and device for delay-free measurement of the air/fuel ratio of combustion systems, especially internal combustion engines, by measuring individual components of the fuel, the ambient air used for fuel combustion, and the exhaust gas, wherein the water vapor concentrations of the exhaust gas and, preferably, the ambient air or the gas supplied for fuel combustion are measured, and wherein the air/fuel ratio are computed by the obtained values and data on fuel composition.

Abstract: In order to prevent crystal seeds with retrograde solubility from dissolving in the hydrothermal growing solution at the beginning of the growing process, and to protect the finished crystal at the end of the growing process, and in order to reach the thermodynamic growth equilibrium as soon as possible, the proposal is put forward that the growing solution be prepared, pre-saturated and pre-heated to a temperature close to saturation temperature outside of the growing tank, and that, for the growing process proper, the hot growing solution be added to the pre-heated growing tank provided with crystal seeds, where it should be further heated to a temperature at which the crystals start growing, and, further, that the hot growing solution be quickly removed from the growing tank as soon as the growing process has been completed.

Abstract: In piecoelectric measuring elements comprising two or more crystal elements that are jointly subject to the mechanical variable to be measured and are provided with electrically conductive electrodes on opposite surfaces located essentially normal to the electric (x) axes of these crystal elements, disadvantages arising from shearing stresses can be prevented by using crystal elements (2) from crystals of point group 32, in which exist two opposite types of enantiomorphism, l and r, in which part of the crystal elements used belong to one of the two enantiomorphic types l or r, and have one of the two absolute orientations of the x-axis, .alpha..sub.1 or .alpha..sub.2, while the remaining crystal elements belong to the opposite enantiomorphic type and have the opposite orientation of the x-axis.

Abstract: In order to reduce the water content in piezoelectric GaPO.sub.4 crystal elements the proposal is put forward that each GaPO.sub.4 crystal element should be cut in its entirety from one uniform growth zone of a GaPO.sub.4 raw crystal bar and should not contain any zone boundaries, and that the piezoelectric GaPO.sub.4 crystal elements should be treated with a dehydrating solution, until an infrared coefficient of .alpha.<1.5 cm.sup.-1 is obtained at a wavelength in the vicinity of 2.0 .mu.m.

Abstract: In conventional methods of quantitative hydrocarbon analysis in gaseous sles by means of infrared transmission, systematic inaccuracies may be found which are caused by changes in the composition of the components contained in the sample. Such inaccuracies typically amount to 10 to 30% of the measured value, with occasional rises of up to 100%. In order to eliminate this disadvantage the invention proposes that for determining the total mass of gaseous and condensed hydrocarbons radiation be used with a frequency band whose integral infrared absorption has approximately the same value for each of the main hydrocarbons present.

Abstract: In order to eliminate equipment-generated fluctuations during the periodic determination of a quantity to be measured which is effected by forming the difference between a measuring signal which has been altered relative to a source signal by the measurement variable and a reference signal which has remained unaffected relative to the source signal by the measurement variable, a base signal level is determined for each measuring cycle as the difference between the reference level and a zero level in the absence of a source signal, subsequent to which each actual reference signal level and each measuring signal level is compensated with the previously determined reference signal level. By amplifying the compensated reference signals prior to difference formation and standardizing the signal difference to the base signal level, a high degree of accuracy may be achieved even if the attenuations of the measuring signal caused by the quantity to be measured are very small.

Abstract: A transducer comprising a flexible piezoelectric layer as a sensor element for measuring mechanical quantities in hollow bodies, above all pressures in pipes, the opposite sides of this layer being bonded to electrically-conductive contact layers and being connectable via leads to a display and evaluation unit. In order to achieve a high temperature stability in such transducers and to make them suitable for use at temperatures exceeding 80.degree. C., the piezoelectric layer is proposed to consist of wurtzite or sphalerite. One of the electrically-conductive contact layers can be of some heat-resistant, flexible supporting material, for instance flexible metal foil, such as Cu-Be foil, or a sheet of plastic, one or both of whose sides are metallized, and the other electrically-conductive contact layer can be a metal coating applied by evaporation.