Determination of temperature corrections for the dimensions of machine details

Conclusions The above semiconductor thermometer with a special transducer is convenient for measuring the temperature of flat, spherical, and fashioned outer and inner surfaces.The special transducer provides temperature measurements lasting not more than 10 sec. The error in measuring temperature does not exceed ±0.3°.The above technique for determining corrections of temperature deviations from the normal of the article and the measuring instrument by means of a semiconductor thermometer and special graphs raises the accuracy of measurement and productivity in manufacturing precision articles on metal-working machines, and reduces the percentage of rejects due to inaccurate measurements.The above technique and instrument can be used under workshop conditions at the bench, in the Technical Control Division (OTK), inspection and test points, in factory test laboratories, and in GKLs for measuring equipment of the State Committee of Standards, Measures, and Measuring Instruments of the USSR.     

Surface acoustic wave characterization of PECVD films on galliumarsenide

Surface-acoustic-wave (SAW) measurement techniques can be effectively used to determine the acoustic properties of dielectric and piezoelectric films. Such films can be used for the development of semiconductor-integrated microwave-frequency surface and bulk acoustic wave devices. The acoustic properties of silicon nitride, silicon oxynitride, silicon carbide, and TEOS glass, deposited by plasma-enhanced chemical-vapor-deposition (PECVD) on GaAs, have been characterized using linear arrays of SAW interdigital electrodes operating in the harmonic mode over the frequency region from 30 MHz to above 1.0 GHz. The elastic constants of these amorphous films have been determined by fitting theoretical dispersion curves to the measured SAW velocity characteristics. Frequency-dependent SAW propagation-loss values have been determined from the observed linear change in loss as a function of transducer separation. Preliminary measurements of the temperature coefficient of frequency (TCF) for SAW propagation of the films on GaAs are also given     

Evaluating the length of a piezoelectric transducer's cable line

Conclusions Taking into consideration that the operating conditions of a piezoelectric transducer preclude the use of a matching impedance at the end of the cable line, a correct selection of the cable length connected to the piezoelectric transducer has a substantial importance in the technique of piezoelectric measurements. The method described above for determiningl _{max per} can be applied successfully in systems for measuring pulsating pressure, acceleration, and vibrations.Translated from Izmeritel'naya Tekhnika, No. Il, pp. 86–88, November, 1969.     

超声波流量计换能器系统理论分析及应用

为了使超声波流量计能够获得最佳的超声波信号,从理论上分析了超声波流量计的换能器系统,在此基础上提出了用收发电压灵敏度参数来表征换能器系统的综合发射和接收性能。采用等效网络理论,计算了超声波压电换能器的发射特性和接收特性,同时给出了收发电压灵敏度的表达式以及在流量计工作频率下换能器的最优设计准则。应用该准则设计并制作了适用于热量表的超声波换能器。实验结果表明:采用该设计理论研制的换能器系统可以使热量表在工作频率上获得最优的超声波信号,同时也证明了采用该理论设计的超声波流量计换能器系统的有效性。     

Remote sensing of mechanical properties of materials using a novel ultrasound transducer and signal processing

An ultrasound-based remote sensing method to evaluate the mechanical properties of materials is presented. This method consists of a disk-shaped, piezoelectric transducer, operating at its resonance frequency, and a phase-shifted, feedback circuit. Mechanical parameters are derived by analyzing the signal contained in the phase-shifted values of the reflected signal. It is concluded that, using this novel transducer system and signal processing, remote mechanical measurements can be made. Such measurements obviate the need to apply the force-deformation approach and may be used to enable stiffness imaging.     

Testing of strain-gauge pressure transducers up to 3.5 MPa at cryogenic temperatures and in magnetic fields up to 6 T

The characteristics of four commercial strain-gauge pressure transducers suitable for measurements in a temperature range from 4.2 to 293 K were determined in the presence of magnetic fields up to 6 T. The highest pressure measured was 3.5 MPa. Tests showed that if the transducers are used in these conditions and no corrections are made, uncertainties up to 19% of the transducer full scale may be inherent in measurements. When such high error levels are unacceptable, the transducers must be individually calibrated under the working conditions: in this way the uncertainties in pressure measurements can usually be kept below 1 % of the transducer full scale.     

Acoustically isolated paired air transducers for 50-, 100, 200-, or500-kHz applications

Solid piezoelectric disks, sealed within a metal case, have a relatively high acoustic impedance Z and exhibit undesirable ringing. Nevertheless, they can be used in a variety of air-coupled ultrasound applications, including industrial applications where robust construction is important. To overcome the drawback of high Z, quarter-wave impedance matchers are necessary. Ringing usually prevents one from using high-Z matched transducers in pulse-echo mode. But if the transducer case is isolated acoustically from the surrounding structure, pairs can be installed side-by-side or in other configurations. It has been found that numerous potential applications become practical if the case contains a circumferential flange that can be sandwiched between a pair of soft O-rings. Applications include measurement of the distance to a reflective target; measurement of flow in the axial direction in a pipe; measurement of secondary flow components such as swirl or crossflow; measurements related to sound speed in a gas, namely, average molecular weight, or temperature; and air-coupled measurements of thickness and elastic properties in solid or porous boards. Designs are presented, showing how one, two, four, or eight transducers can be installed in standard 1-, 2-, or 3-inch pipe plugs or 2-inch flanges. A 2-inch pipe plug accommodates two transducers, while a 2-inch flange is big enough to contain eight transducers, e.g., pairs operating at 50, 100, 200, and 500 kHz. Combining transducers of different center frequencies partly overcomes the narrow bandwidth of any individual transducer     

PIMNT单晶弯曲圆盘换能器设计

新型弛豫铁电单晶材料铌铟酸铅-铌镁酸铅-钛酸铅晶体(Pb(In_1/2Nb_1/2) O₃-Pb(Mg_1/3Nb_2/3) O₃-PbTiO₃, PIMNT)的压电系数是陶瓷材料的 6 倍以上,应变量高出压电陶瓷 10 倍以上,具有较高的机电耦合系数,压电性能优于传统 PZT 材料。文章将单晶材料应用于带空气腔的弯曲圆盘换能器中,利用 ANSYS 仿真软件优化换能器结构,确定换能器尺寸,设计制作 PIMNT 压电单晶换能器和PZT4压电陶瓷换能器,并进行了水池实验。换能器实测结果与仿真结果保持一致,单晶换能器的谐振频率为 2.85 kHz,最大发送电压响应为 136.3 dB。结果表明,相比于同尺寸的陶瓷换能器,将 PIMNT 压电单晶应用于弯曲圆盘换能器可降低谐振频率,提高发送电压响应,提升换能器的工作性能,为进一步改善单晶换能器综合性能提供参考。     

Method for measuring physical quantities of parametric converters

Conclusion The considerations expressed above lead to the conclusion that this method can be used with adequate efficiency for measuring physical quantities by means of parametric converters. The main advantages of the method consist in its high sensitivity, reliability, simplicity, linearity over a wide range of the measured parameter, and the possibility of converting the value of the primary transducer parameter directly into a digital code.On the basis of this measurement method it is possible to design CCS input and multichannel measurement devices which meet the requirements of reliability, precision and operating speed [9],The above conclusions are in good agreement with the results of testing measurement circuits and models of CCS input devices.     

Optimization of parameters for silicon planar source of modulated infrared radiation

We report on the performance of planar silicon diodes operating in the double injection mode and emitting modulated infrared radiation at temperature range above 300 K. Results present theoretical analysis and experimental verification of an optimization aimed at maximal difference between emissivity of this structure for cases with and without forward bias applied to p-n junction. Several advantages of the structures were shown: wide emission spectrum (3÷12 μm), short rise-fall time (300 μs), high operating temperature (≈400 K). These planar photonic sources can be used as easily controlled sources of modulated infrared radiation in wide spectral range, image simulators, e.g. dynamic scene simulation devices with frame frequencies well above 200 Hz and for measurements of thermovision camera dynamic parameters.     

The accuracy of an angular-displacement transducer

Conclusions The above method can be used to check photoelectric transducers of angular displacement under static operating conditions.Integration of the signals from n groups of lines enables one to reduce the transducer error by averaging the random components of the errors in the positions of the lines and the errors in their widths and consequently enables one to use comparatively rough graduated circles in the construction of highly accurate instruments.Translated from Izmeritel'naya Tekhnika, No. 9, pp. 40–41, September, 1978.     

燃油流量高精度计量的研究

分析了涡轮流量传感器的工作原理。研究了由于燃油的温度变化引起的传感器本身尺寸变化、燃油密度变化给计量精度带来的影响。在温度、压力可调整的燃油实验装置上对传感器进行了实验研究。发现可以用线性公式来描述质量仪表系数随温度变化的规律；质量仪表系数的绝对变化量、相对变化量可近似为恒定值。提出了两种温度补偿方法，可分别得到优于0．2％和优于0．25％的质量流量计量精度。     

Selection and computation of optimum frequencies for double-parameter grain moisture meters

Conclusions The principle described above for selecting and computing optimum frequencies for double-parameter moisture-content meters can be applied to materials with disturbing parameters which are not accessible for direct measurements, such as the density of a grain and air mixture.On the basis of the derived condition (8) it has been shown that for a continuous testing of moisture content in grain with the elimination of the disturbing density parameter it is advisable to operate at frequencies of 20 kHz, which is the most sensitive to moisture changes, and at 5–10 MHz, which are the most sensitive to density variations.In this connection it should be noted that in single-frequency testing of moisture content in grain freely poured into a transducer, or in testing flowing grain, the errors due to density changes are smaller at the lower frequencies up to 250 kHz.On the basis of experimental data (see Fig. 4) it can be easily shown that in using a double-frequency method for evaluating moisture content in grain freely poured into a transducer, or in flowing grain, the measurement error amounts to ±0.25% of the absolute moisture-content value.The above technique can be applied to other types of bulk materials which are suitable for frequency separation (9).     

Feasibility of noncontact intracardiac ultrasound ablation and imaging catheter for treatment of atrial fibrillation

Atrial fibrillation (AF) affects 1% of the population and results in a cost of 2.8 billion dollars from hospitalizations alone. Treatments that electrically isolate portions of the atria are clinically effective in curing AF. However, such minimally invasive catheter treatments face difficulties in mechanically positioning the catheter tip and visualizing the anatomy of the region. We propose a noncontact, intracardiac transducer that can ablate tissue and provide rudimentary imaging to guide therapy. Our design consists of a high-power, 20 mm by 2 mm, 128-element, transducer array placed on the side of 7-French catheter. The transducer will be used in imaging mode to locate the atrial wall; then, by focusing at that location, a lesion can be formed. Imaging of previously formed lesions could potentially guide placement of subsequent lesions. Successive rotations of the catheter will potentially enable a contiguous circular lesion to be created around the pulmonary vein. The challenge of intracardiac-sized transducers is achieving high intensities (300-5000 W/cm2) needed to raise the temperature of the tissue above 43 degrees C. In this paper, we demonstrate the feasibility of an intracardiac-sized transducer for treatment of atrial fibrillation. In simulations and proof-of-concept experiments, we show a 37 degrees C temperature rise in the lesion location and demonstrate the possibility of lesion imaging.     

A digital signal-processing technique for compensating ultrasonicsensors

A factor of great importance when assessing the accuracy of ultrasonic rangefinders is the accuracy in the knowledge of the speed of sound, necessary to convert temporal into spatial information. A digital signal-processing technique for making an ultrasonic transducer array capable of automatically compensating for variations in the speed of sound due to temperature or any other atmospheric conditions is proposed and discussed in this paper. The technique is based on an iterative linearized least-squares estimator, namely an extended Kalman filtering algorithm, for processing the time-of-flight measurements from a reference target whose location is only approximately known. In contrast to other well-known techniques, neither additional external sensors for monitoring the environment nor accurately positioned reference targets are required. A sensitivity analysis of the proposed algorithm is performed through a Monte Carlo simulation study. The theoretical analysis provides a clear-cut picture for understanding the merits of the technique under a variety of physical operating conditions. The level of the measurement noise and the correct calibration of the transducers are proven to be the crucial factors for obtaining estimates of the speed of sound at a prescribed level of accuracy, given a fixed temporal interval for collecting the measurements. The main conclusions of the simulation study are confirmed by some real-life results obtained using an experimental tracking sonar device     

Contrast medium assisted fluid flow measurements

In this paper the development and evaluation of two new approaches for ultrasound time-domain fluid flow measurements by tracking echoes scattered by a contrast agent following injection of a bolus of the contrast agent are described. Their feasibility was investigated by measuring velocity or velocity profile of blood flowing in a mock circulatory loop in vitro. Measurements were made with a one transducer intravessel approach and a two transducer extravessel approach. A hybrid cluster or vector cross-correlation method was used to track the motion of the scatterers in the two transducer time-domain method. This cluster or vector cross correlation method was developed to reduce the ambiguity resulted from misregistration which is a common problem in target tracking by correlating signal patterns. The experimental results show a good agreement between the measured data and those estimated from timing the volume. Although the discussions given in this paper pertain only to blood flow measurements, there is no reason to indicate that these approaches can not be used for fluid flow measurements in an industrial environment if suitable contrast agents can be developed     

Realization of the 3He Vapor-Pressure Temperature Scale and Development of a Liquid-He-Free Calibration Apparatus

The ³He vapor-pressure temperature scale was realized using an apparatus based on a continuously operating ³He cryostat at the National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST). The cryostat has two operational modes: a ³He circulation mode and a 1 K pot mode. The ³He circulation mode can be used for ³He vapor-pressure measurements below 1.6 K, and the 1 K pot mode can be used for measurements above 1.3 K. Either mode can be selected for measurements from 1.3 K to 1.6 K. The realization of the ³He vapor-pressure temperature scale in this study fully covers its defined temperature range from 0.65 K to 3.2 K in the International Temperature Scale of 1990. The latest realization results are presented in this article. In addition, a liquid-He-free calibration apparatus was developed. It does not require liquid helium as a cryogen, which usually entails cumbersome handling and periodic refilling. The apparatus was designed for the calibration of capsule-type resistance thermometers from 0.65 K to 24.5561 K (the triple point of neon). The cooling system of the apparatus consists of a commercially available pulse-tube refrigerator and a ³He Joule?CThomson (JT) cooling circuit developed at NMIJ/AIST. The pulse-tube refrigerator is used in a pre-cooling stage and cools the apparatus to approximately 5 K. The ³He JT cooling circuit is used to cool the apparatus from 5 K to below 0.65 K. Since the ³He JT cooling circuit is a closed circuit, the apparatus can run continuously with only simple maintenance required. The basic characteristics of the apparatus are described.     

High-precision magnetic field-strength meter

Conclusions The above meter can be used as a reference instrument for checking other magnetic field-strength meters, and can be used as required in metrological and physical investigations for precision measurements of the strength of uniform magnetic fields.The values of the constants for measuring probes given in this article can be recommended for use in computations in magnetic-field measurements by nuclear meters using the resonance of protons, lithium nuclei and deuterons.     

Experimental determination of the time constant in propeller tachometric flowmeter transducers

Conclusions The above method of simulating a sudden change in the rate of flow by clamping the rotating part of a flowmeter transducer for the purpose of determining its time constant is very simple and easy to produce, and can be recommended for application in any laboratory or workshop. This method can be applied to flowmeters and other similar instruments.     

Capacitive analog transducer of large displacements

Conclusions Test results indicate that a linear analog capacitive transducer is suitable for indicating displacements over a wide range with an error not exceeding 2·10_–5. The design relationships and formulas provided above can be used for evaluating the structural factors and parameters of the transducer, which affect its precision, and to make the transducer meet given requirements with a minimum of trimming work. A capacitive linear analog converter of displacements into an ac voltage amplitude is a sufficiently simple device which can be widely used in systems requiring precise measurement of large displacements and lengths.Translated from Izmeritel'naya Tekhnika, No. 8, pp. 15–18, August, 1968.