基于AVR单片机的低压集中抄表终端

电力行业中,采用低压集中抄表终端对一个配电区域的电能信息进行自动采集和控制是一种发展趋势。现在以AVR单片机为核心,研制出一种低成本、性能稳定的低压集中抄表终端,能对它所连接的电能表的参数、各类电能数据和事件数据进行设置、采集和存储,并在主站计算机召测时发送给主站。     

Response of a slotted orifice flow meter to an air/water mixture

The ability of a flow meter to respond predictably to the presence of liquid and gas is important to the natural gas industry and to users of steam. In both cases, the gas can become saturated and some liquids can condense in the line. The response of orifice flow meters to the presence of liquids is erratic and produces considerable uncertainty. Turbine flow meters can sustain severe damage when subjected to two phase flow. The slotted orifice flow meter has been developed to address the problem of upstream flow conditioning. This device has been shown to be insensitive to the upstream velocity profile. To further evaluate the flow meter for use by the natural gas industry, the effects of adding liquid to a gas flow upon the meter performance has been investigated by subjecting a slotted orifice flow meter with an equivalent β ratio of 0.50 to a two phase flow consisting of air and water.     

Micro optical power meter for direct in situ measurement of light transmitted from microscopic systems and focused on micro-samples

This paper reports a micro optical power meter which is able to perform effective and precise measurement on the optical power at the focus of different microscopic systems. The power meter can be easily placed on the stages of different microscopes and even partly immersed into solution to directly measure the optical power transmitted from the microscope objective and focused on the sample suspended in solution. The testing experiments demonstrated that the power meter has the characteristics of high precision, excellent linearity, high sensitivity, good stability, and high responding speed. It can accurately measure power levels from 0.1 to 50 mW in visible wavelength in various conditions and environments, which may encounter in practical applications. The optical power measurements using the power meter performed in some biological cell culturing solutions and in air for the same laser light reveal the first time that the powers measured in solutions were about 5%-8% greater than that measured in air at the same position. This not only suggests the necessity of performing direct measurement in situ in solution to obtain the real optical power projected on the suspended samples, but also indicates that such a micro optical power meter can meet almost all the requirements of optical power measurement in different fields from biomedicine to material sciences.     

Automatic transformation between water level meter measurement data and altitude on the large-scale physical model

The water level is one of the most important physical parameters of the physical model experiment. A large-scale physical model usually has many water level meters, It is an important basis for the accurate simulation of the water level to determine the transformation relationship between those level meters readings and the altitude in the prototype. Based on collimated characteristics of laser and image processing by binarization of gray image and character segmentation, an automatic transformation system was developed to improve transformation accuracy. The main idea is to use laser scanner to build a reference plane, then light illuminates the water level meter, so that the CCD on the top of the water level meter could gather the laser beam and convert light intensity to image signals. With further image processing, such as threshold transformation, the system can get the coordinate of laser center. Due to the fixed relationship between the coordinate and the water level meter measurement data, then the system can found transformation relation between water level meter and altitude automatically. Experiments show that comparing with the manual calibration, relative error of automatic calibration water level meter altitude conversion decreased from ±1.34% to ±0.19%.     

Pressure drop of wet gas flow with ultra-low liquid loading through DP meters

The most common method to predict the gas and liquid flow rates in a wet gas flow simultaneously is to use dual pressure drops (dual-DPs) from two or even one single DP meter. In this paper, the metering mechanism of applying dual-DPs were overviewed. To fully understand the response of DP meters to wet gas flows, the pressure drops of wet gas flow with ultra-low liquid loading through three typical DP meters were experimentally investigated, including an orifice plate meter, a cone meter and a Venturi meter. The equivalent diameter ratio is 0.45. The experimental fluids are air and tap water. The pressure is in the range of 0.1–0.3 MPa and the Lockhart-Martinelli parameter (X_LM) is less than approximately 0.02. The results show that the upstream-throat pressure drop, the downstream-throat pressure drop and the permanent pressure loss of individual DP meters have unique response to liquid loading. The upstream-throat pressure drop of the orifice plate meter decreases at first and then increases as the liquid loading increases, while that of the cone meter and the Venturi meter increase monotonically. The non-monotonicity of the pressure drop for the orifice plate meter can be attributed to the flow modulation of trace liquid. The downstream-throat pressure drops of all the three test sections decrease at first and then increase. The reason is that the liquid presence in a gas flow increases the downstream friction and vortex dissipation. The permanent pressure loss of the orifice plate meter also shows non-monotonicity. To avoid non-monotonicity, the pressure loss ratio is introduced, which is defined as the ratio of the permanent pressure loss to the upstream-throat pressure drop. Results show that the pressure loss ratio of the Venturi meter has the highest sensitivity to the liquid loading.     

Analysis methodology of movable emittance-meter measurements for low energy electron beams

The design of photoinjectors for modern free electron laser linac relies heavily on particular beam behavior in the few meters after the gun. To experimentally characterize it a movable emittance meter was proposed and built [L. Catani et al., Rev. Sci. Instrum. 77, 093301 (2006)] based on the beam slicing technique. This paper addresses all the aspects of analysis of the data acquired with the emittance meter and common to any slit based emittance measurement for low energy beams.     

Autonomous algorithm for relative error of generalized flow meters in tree topology

This paper treats electricity meters or water meters on-site as a cluster of generalized flow meters constructing a tree topology. Providing flow conservation, it is demonstrated that every meter’s relative error can be calculated according to a group of readings of the meter cluster if the relative error of any meter in the cluster is given. The autonomous algorithm obtains relative errors without usage of external standard instrument. By the same algorithm, providing the accuracy class of any meter rather than the relative error exact, the range of relative errors of rest meters in the cluster can be worked out. With the aid of remote automatic reading system, the algorithm can reduce the maintenance cost of meters on site, and contributes to forecast the meters’ service lives.     

The performance characteristics of a micro-machined Coriolis flow meter: An evaluation by simulation

Micro-machined Coriolis meters will enable measurement of very low flow rates (0.1–500 g/h) and, potentially, ultra-low flows (0.1–100 mg/h). Application areas include the delivery of medical drug infusions to patients, and a wide variety of micro-fluidic devices. An evaluation of the performance of two prototype micro-machined flow-tubes of differing shapes is reported, based upon results obtained from a virtual Coriolis meter. This tool comprises a finite element modelling capability which simulates the meter flow-tube in motion, with the flow represented simply as a continuous string, i.e. 1-dimensional and frictionless, and the model allows the generation of pseudo-data at points on the tube corresponding to sensor locations. Application of signal processing algorithms then enables the representation of an indicated flow time history output by a Coriolis meter in response to a prescribed input flow. Results indicate that the devices investigated were all highly linear and that meter sensitivity is independent of fluid density. One flow-tube shape confers higher stiffness than the other and, for both tube shapes, increasing wall thickness increases tube stiffness at a greater rate than the tube mass. Higher stiffness results in reduced meter sensitivity, but increased drive frequency (hence, faster dynamic response). The spatial averaging resulting from the use of ‘distributed’ internal sensors inevitably yields meter sensitivity values that are lower than the potential maximum value that might be achieved by use of ‘point’ sensors; however there are practical reasons why this latter approach would not work. The dynamic response to a flow step is essentially the same as found for macro-Coriolis meters.     

变电站指针式仪表检测与识别方法

受限于复杂的电磁环境,变电站中的大量模拟式仪表需要人工读取示数,不利于变电站自动化管理。而目前针对仪表自动读数方法的研究大多基于预先获取到的高质量图像,其中仪表目标位于图像中央且占比较大,仪表表盘与相机平面平行,这需要大量预先的仪表测量与相机标定工作,不能满足实际电站环境下的使用要求。为解决上述问题,提出了一种完整的变电站指针式仪表的自动检测与识别方法。首先利用卷积神经网络模型检测当前视野下仪表目标的包围框位置,计算其距离视野中央的偏离值与图像占比,据此调整相机位置和缩放倍数。通过透视变换消除表盘平面与相机平面偏差造成的仪表图像畸变,通过霍夫变换检测仪表的表盘与指针,完成仪表读数识别。变电站实际测试实验结果表明,本方法最大读数误差仅为1.82%,对于复杂背景下多类别仪表的自动检测与识别任务具有良好的准确性与稳定性,可满足变电站实际应用需求。     

An Astigmatic Wavelength Meter

An astigmatic scheme of a laser wavelength meter based on a single air-gap Fizeau interferometer is described. For a multimode laser, the accuracy in determining the center of gravity of a spectrum is within 1 GHz. Two complementary testing techniques are proposed for the instrument. By using them, it was shown for the first time that, for this type of meters, a systematic error arises and increases with a decrease in the radiation-spectrum width. The effect is periodic in the lasing frequency and results from a weak beam that is brought about by a reflection from the front surface of the interferometer. Moreover, in the previously designed optical schemes, this effect is so strong that unambiguous determination of the wavelength of a single-frequency radiation is impossible. The use of an astigmatic scheme helps additionally attenuate the influence of the third beam, thus eliminating the ambiguity in the results and reducing the absolute error to a value of ±1.5 GHz.     

A high-performance meter for measuring transverse defects in sheet products

High-precision and environmentally friendly measurement of sheet product parameters is an important problem. Well-known environmentally friendly high-precision optical triangulation meters for measuring the parameters of sheet products enable one to measure the parameters only for longitudinal defects in sheet products. It is shown here that the modernization of a high-precision optical triangulation meter designed for measuring longitudinal defects in sheet metal allows trans-verse defects to be precisely measured in sheet products as well. Such a meter allows one to control the main rolling parameters in addition to measuring the longitudinal defects in sheet products. This provides environmentally friendly production of high-grade sheet products.     

The identification of external factors which influence the calibration of Coriolis massflow meters

It has been suggested that, by monitoring the sensor signals and the meter drive signal, it may be possible to create a Coriolis meter which can identify the presence of a variety of external disturbances and can give a warning and/or make a correction to the meter output in order to maintain accuracy. This paper presents the findings from an investigation of the response of commercially available Coriolis meters to such disturbances. The results of this program of tests are reported and the implications of these results on the practicality of the creation of an ‘intelligent’ meter are discussed.     

基于固有安全的多功能辐射测量仪

为实现固有安全光辐射防爆技术,评定设备的光束强度,设计了一个多功能辐射测量系统。分析光电转换器的检测原理,选择光电池和PIN光电二极管作为光电转换模块核心元件,并设置了模式切换,以完成不同种类光信号的采集。经过后续电路的信号处理,最终实现连续光波辐射的平均功率、脉冲辐射的峰值功率以及脉冲能量的测量。这种用于防爆的专用测量仪能够提供整体的光辐射设备防爆技术测量方案,具有实际的应用价值。     

Monitoring of coal separation in a jig using a radiometric density meter

This paper discusses the application of a radiometric density meter to monitor the coal separation process in a jig. The signal from the meter can be used to evaluate the degree of coal grain loosening during cyclic water pulsations and to determine the separation density in the jig. The signal from the radiation detector is highly variable due to stochastic decay of the radiation source and various changes in media density. The paper shows how to optimize the analogue and discrete filters applied in an electronic circuit of a density meter. The minimum dynamic error of measurement can be achieved if their parameters adapt to changes in the measured density. The authors present results of industrial tests carried out on the jig control system with the radiometric density meter.     

基于光纤布拉格光栅和压电转换器的电功率传感器

针对传统功率计测量电功率存在线圈电感、电容与金属部分的涡流感应等限制,本文基于布拉格光纤光栅与压电转换器设计了电功率传感器来测量实功率与虚功率.将布拉格光纤光栅粘贴于压电转换器上,构建了动态应变模拟装置.负载电压与负载电流的乘积形成的等效电压施加在压电转换器上使布拉格光纤光栅动态变化,由此测量光栅动态变化所造成的波长改...     

Experimental determination of the dynamic response of Coriolis mass flow meters

The dynamic response of Coriolis meters is significant in many applications, including fast control operations, e.g. short duration (seconds or less) batch-filling, dosing flows, and the potential for application to static gas turbine engine fuel flow control. The dynamic response of a meter is determined firstly by the dynamic response of the flow tube (as detected by the two motion sensors) and subsequently by the data sampling and signal processing algorithms used to extract the phase-difference to generate the user output. The flow tube dynamic response and meter indicated response (pulse output) were determined experimentally for a number of commercially available meters, by subjecting each meter to step changes in flow rate. The fastest steps achieved were of duration 4.5 ms. It has previously been shown that the meter flow tube response time, as extracted through phase-difference measurements, cannot be less than the duration of one drive cycle of the tube vibration. Correspondingly, flow tube dynamic response times in the range of 1.4–10 ms were observed (for meter drive frequencies (approximate) in the range of 700–100 Hz). As predicted by theory (straight tube) and finite element simulation, the flow tube step response also includes contaminating (noise) components associated with the Coriolis frequency. There are indications that this noise amplitude was increased by mechanical vibration effects induced by the flow step mechanism. As expected, the meter user output (pulse) indicated much slower step responses than those of their respective flow tubes. These outputs were characterised by a delay in the onset of the step and subsequent lengthening of the step duration which was associated with the output update rate. In some cases, the step noise was apparently eliminated in the user output and this effect was enhanced by the relatively slow update rate.     

Water density formulations and their effect on gravimetric water meter calibration and measurement uncertainties

In the gravimetric calibration method of water meters, the volume of water that has passed through the equipment under test (EUT) is generally collected into a tank and the quantity (mass) determined by weighing. The mass of water collected is then converted into a volume. This conversion of mass into volume requires knowledge of the water density, which can be estimated, measured directly or determined by other means. The error of measurement of the EUT is determined by comparing the volume recorded by the EUT and the volume collected in the tank. The density of water is, therefore, one of the major causes of measurement uncertainty in laboratory calibration of water meters using the gravimetric method. Water meter calibration facilities commonly use density formulations proposed by the International Standards Organisation (ISO) and the Organisation for International Legal Metrology (OIML). In Australia, additional guidance in water density determination is provided by the National Measurement Institute (NMI). In this study, testing was undertaken using ten positive displacement water meters arranged in series in the test rig to evaluate some of the common water density formulations used in Australia. The effect of these different formulations on the water meter error measurement was determined, as well as the effect on the measurement uncertainties. The results shows that the use of these different density formulations evaluated do not significantly affect the water meter error of measurement or the uncertainty of measurement. There was no apparent correlation between the water meter error and the meter position in the test rig. It was also determined that if the water density was adjusted only for temperature effects, a maximum of 0.05 and 0.15% drift in meter error and measurement uncertainty respectively, can be expected.     

浅谈电能表是否合格的验证

阐述了校验电能表正确接线方法,通过电能表校验方法步骤及技术要求,论证了电能表能否正常计量、正常安装运行。     

Numerical simulations for multi-hole orifice flow meter

The measurement of flow rate is important in many industrial applications including rocket propellant stages. The orifice flow meter has the advantages of compact size and weight. However, the conventional single-hole orifice flow meter suffers from higher pressure drop due to lower discharge coefficient (Cd). This can be overcome by the use of multi-hole orifice flow meter. Flow characteristics of multi-hole orifice flow meters are determined both numerically and experimentally over a wide range of Reynolds numbers. Computational fluid dynamics (CFD) is used to simulate the flow in the single- and multi-hole orifice flow meters. Experiments are carried out to validate the CFD predictions. The discharge coefficients for the different orifice configurations are determined from the CFD simulations. It is observed that the pressure loss in the multi-hole orifice flow meter is significantly lower than that of single-hole orifice flow meter of identical flow area due to the early reattachment of flow in the case of the multi-hole orifice meter. The influence of different geometrical and flow parameters on discharge coefficient is also determined.     

On the use of TEM cells for the calibration of power frequency electric field meters

This paper focuses on the performances of TEM cells when used in the calibration of power frequency environmental electric field meters. The spatial non-uniformity of the electric field inside a TEM cell is analyzed through experimental investigations and three-dimensional Boundary Element modeling to evaluate the field experienced by the sensing elements of actual 3D meter probes. The perturbation caused by the probe support is also taken into account. The uncertainty component associated with the spatial non-uniformity in the volume taken up by typical power and low frequency field probes is estimated. The field non-uniformity is also evaluated in relation to the use of TEM cells of reduced size. Finally, the field non-uniformity is exploited to predict the performance of an actual field meter operating in significant field gradients.