In present paper, the focus is given to possible ways of increasing accuracy for existing ultrasonic time-of-flight water meters. We will consider transducers with coaxial reflectors working at laminar, transitional and turbulent regimes within their measurement range. Considering error curves of such meters, we can easily resume that they are non-linear and not simply corrected using only one polynomic function. Measurements in laboratory and field conditions demonstrate that there is a shift in the ultrasonic meter’s calibration factor. The deviation of readings starts at Re = 5 000–10 000 and the maximum value is reached at Re = 160. Great inaccuracies referred to the transition from laminar flow to turbulent take place abruptly, which lead to undesirable errors. To understand this phenomenon, the theoretical basis of ultrasonic measurements was analyzed and revealed that typical algorithm for determination of the calibration factor is very questionable since it contains simplified information about velocity profile distribution. Trying to fix this problem, we applied computational fluid dynamics (CFD) modelling of ultrasonic meters with different variants of flow straighteners. Ranges of applicability of a particular turbulence model for a correct description of the velocity profile and other flow parameters in metrological purposes have been evaluated. Due to applied techniques, the flow profile sensitivities of various meter configurations are investigated at different Reynolds numbers comparing to real experiments. To get an improved ultrasonic meter design recirculation zones and flow separation regions inside the flow transducer have been eliminated. As a result, the accuracy of the ultrasonic water meter has increased. Simulations demonstrated reasonable agreement to the error curves obtained on the calibration facility for a whole measurement range.

con 5 (100), which has high elastic characteristics. The analysis of real products for resonance and the ability to modify them in order to remove from the range of forbidden eigenfrequencies remain an actual problem in the design of sensitive elements of the pendulum micromechanical accelerometers. The main constructive node of the micromechanical accelerometer is a sensitive element which includes mass and elastic elements of the suspension, is attached to the support frame (base). Elastic elements of the suspension are located on the console or bridge scheme. Under the bridge scheme, the suspension M moves strictly along the measuring axis. Multilayer bridge suspension M is characterized by low sensitivity to transverse actions, high rigidity and basic self-frequency. The dynamic analysis seeks to calculate of the resonant (own) frequencies and their corresponding forms of oscillation. The module COSMOSWorks implements the classical finite elemental method, which has the following limitations: damping is not taken into account; the presence of friction is ignored; the external load which changeable is absent. The consequence of the first limitation is the inability to obtain information on the state of the design at the moment of resonance. None of the parameters (displacement, deformation, stress) is not calculated. Also, the analysis of behavior during loading of loads is not available. However, even with these restrictions, the program allows you to solve the most urgent task -to perform the analysis of real products on the resonance and to modify them in order to remove from the range of forbidden eigenfrequencies. The finite element method was used to study influence of the geometric parameters of the elastic suspension and the mass of the sensitive element on the frequency of natural oscillations with correction for damping. In the modeling of suspensions of different shapes, a stress-strain state of the sensitive element was determined and an analysis of the elastic characteristics was conducted to select the optimal design.

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The absence of computer-aided design systems with the choice of flow transducers (FT) for energy resource supply systems determines the relevance criteria developing for evaluating flow transducers effectiveness for liquids and gases. It is advisable to carry out FT optimization with flow bodies by determining rational forms and parameters of hydraulic channel and sensitive element (SE). The FT accuracy can be estimated depending on its purpose, operating conditions and the nature of the measured medium movement: from a probabilistic accuracy index, by the dynamic error index and the generalized efficiency criterion. The last criterion is based on the criteria for the interaction effectiveness of the measured medium flow with the transducer SE and ensures high sensitivity of the system and measurement accuracy with minimal impact on the parameters of the measured medium. The article presents the results of the evaluation of the flow asymmetry influence induced by the spatial knee on the operation of transducers with sensitive elements of various spatial forms. The measurement means with a cone-type flowed body directed apex towards the flow are the best under the conditions of minimum error and minimal effect on the measured medium. The obtained results make it possible to clearly determine the instrument installation place in the technological network under conditions of maximum accuracy and minimal impact on the measured medium.

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