Complex permittivity measurement using capacitance method from 300 kHz to 50 MHz

Complex permittivity measurement has been performed using a parallel plate capacitor and a vector network analyzer (VNA) from 300 kHz to 50 MHz. The material under test (MUT) is a flat and thin sample clamped between the capacitor plates and connected to the VNA to obtain its two port S parameters. The S parameter is converted into impedance to calculate the complex permittivity using Matlab program. Techniques used to overcome the air gap and stray capacitance was described. Measurement obtained using the proposed method was compared with the free space method to validate its accuracy. The percent difference is less than 5%.     

Determination of complex permittivity and permeability of lanthanum iron garnet filled PVDF-polymer composite using rectangular waveguide and Nicholson–Ross–Weir (NRW) method at X-band frequencies

In our previous work, the lanthanum iron garnet-filled PVDF-polymer nanocomposite has been prepared. The reflection and transmission coefficients (S-Parameters) of PVDF-13% LIG were measured using rectangular waveguide in conjunction with a microwave vector network analyzer (VNA) at X-band frequencies (8–12 GHz). In order to determine simultaneously the real and imaginary parts of complex permittivity and permeability of nanocomposite sample the Nicholson–Ross–Weir (NRW) method was applied based on the measurement of the S-Parameters of the materials. The general observations of the results indicate that the decreasing in real and imaginary part of complex permeability and real part of complex permittivity resulted in increasing the frequency; meanwhile imaginary part of permittivity tends to become constant when frequency increased.     

Ordinal measurement,preference aggregation and interlaboratory comparisons

The classical problem of a single consensus ranking determination for m rankings of n alternatives has a potential of wide applications in information technologies, and particularly in measurement and instrumentation. The Kemeny rule is one of deeply justified ways to solve the problem allowing to find such a linear order (Kemeny ranking) of alternatives that a distance (defined in terms of a number of pair-wise disagreements between rankings) from it to the initial rankings is minimal. But the approach can result in considerably more than one optimal solutions what can reduce its applicability. By computational experiments outcomes, the paper demonstrates that a set of Kemeny rankings cardinality can be extremely large in small size cases (m = 4, n = 15 … 20) and, consequently, special efforts to build an appropriate convoluting solution are needed. Application of the model to one of practical metrological problems, such as interlaboratory comparisons, is proposed and examined.     

Kinematic calibration analysis of 3SPS + 1PS bionic parallel test platform for hip joint simulator

As the key component of the parallel hip joint simulator, 3SPS + 1PS bionic parallel test platform owns four degrees of freedom including three rotations and one translation. When the moving platform stays at a given translation position, the parallel manipulator can represent three-dimensional rotating gait motions of the hip joint for the purpose of evaluating the friction characteristics of biological materials. Because of the manufacturing and assembling errors, the actual structure parameters of the parallel manipulator are not more accurate than the theoretical values and its reduced simulation accuracy will bring the uncertain evaluation. So in order to improve the precisions in the design, manufacture and assembly of the parallel manipulator, it is necessary to calibrate the kinematic parameters. Considering the structural characteristics of the parallel manipulator, its error model and the corresponding compensation method are established based on the complete differential-coefficient theory. According to the constant values of two orientation angles, the orientation residual matrix is constructed by adopting the incomplete measurement method and the forward kinematics functions, so its cost function can be defined. The iterative algorithm based on the least square method is applied to identify the structure parameters and obtain their optimal solutions, and then the actual kinematic calibration process is simulated by numerical method. The simulation results show that the comprehensive orientation error after calibration is greatly decreased, and the effectiveness of the calibration method is validated.     

Development of high-precision micro-coordinate measuring machine: Multi-probe measurement system for measuring yaw and straightness motion error of XY linear stage

Today, with the development of microsystem technologies, demands for three-dimensional (3D) metrologies for microsystem components have increased. High-accuracy micro-coordinate measuring machines (micro-CMMs) have been developed to satisfy these demands. A high-precision micro-CMM (M-CMM) is currently under development at the National Metrology Institute of Japan in the National Institute of Advanced Industrial Science and Technology (AIST), in collaboration with the University of Tokyo. The moving volume of the M-CMM is 160 mm × 160 mm × 100 mm (XYZ), and our aim is to achieve 50-nm measurement uncertainty with a measuring volume of 30 mm × 30 mm × 10 mm (XYZ). The M-CMM configuration comprises three main parts: a cross XY-axis, a separate Z-axis, and a changeable probe unit. We have designed a multi-probe measurement system to evaluate the motion accuracy of each stage of the M-CMM. In the measurement system, one autocollimator measures the yaw error of the moving stage, while two laser interferometers simultaneously probe the surface of a reference bar mirror that is fixed on top of an XY linear stage. The straightness motion error and the reference bar mirror profile are reconstructed by the application of simultaneous linear equations and least-squares methods. In this paper, we have discussed the simulation results of the uncertainty value of the multi-probe measurement method using different intervals and standard deviations of the laser interferometers. We also conducted pre-experiments of the multi-probe measurement method for evaluating the motion errors of the XY linear stage based on a stepper motor system. The results from the pre-experiment verify that the multi-probe measurement method performs the yaw and straightness motion error measurement extremely well. Comparisons with the simulation results demonstrate that the multi-probe measurement method can also measure the reference bar mirror profile with a small standard deviation of 10 nm.     

A three-point-probe method for measuring resistivity and the Hall coefficient using Hall devices with minimal design complexity

A novel empirical method for express measurement of resistivity and the Hall coefficient, i.e. the sign, the concentration and the bulk mobility of the majority carriers in semiconductor (silicon) wafers is presented and tested. This approach is based on the parallel-field Hall devices with minimal design complexity containing only three contacts–two input and one (Hall) output. The unique simplicity of this three-point-probe method, the lack of numerical coefficients’ calculation and particular requirements for the geometrical dimensions, probe spacing, wafer form, etc. allows to obtain the necessary information following experimentally clear and technically reproducible steps. The data obtained from non-structured n- and p-type silicon wafers at carrier’s concentration of 10¹⁵ ? n; p ? 10¹⁶ cm⁻³ by appropriate probe arrangements corroborate very well with the results from wafers’ certificates and the results obtained using common measurement techniques. The error does not exceed 5–6% which is about the same as the accuracy of other approaches used for this purpose. The results are especially promising in IC fabrication and complementing the classical Van der Pauw method.     

Simple and simultaneous measurement of five-degrees-of-freedom error motions of high-speed microspindle: Error analysis

We have developed a simple and low-cost optical measurement system for the simultaneous measurement of the five-degrees-of-freedom error motions of high-speed microspindles. We demonstrated the usefulness of the system by using it to measure actual spindle rotation errors, and analyzed the major error factors. First, the measurement error due to the form error of the lens was analyzed by ray tracing. Second, we analyzed the measurement error due to a displacement of an irradiation laser point on a 3 mm diameter ball lens. Furthermore, we investigated the effect of the centrifugal force and the crosstalk problem of multiple laser beams. The results indicated that a form error of the rod lens significantly affected the measurement accuracy and that a change in the laser beam irradiation point of the ball lens due to a radial displacement had no significant effect on the measurement accuracy. Finally, we confirmed that, owing to the centrifugal force, the measurement accuracy decreased as the speed of rotation increased, and that there was no crosstalk that the reflected and transmitted laser beams in the X direction were detected by the photodiode in the Y direction for displacements within −10 to 10 μm.     

The calibration and error compensation techniques for an Articulated Arm CMM with two parallel rotational axes

The calibration and error compensation techniques for an Articulated Arm Coordinate Measuring Machine (AACMM) with two parallel rotational axes are proposed. An improved six-parameter D–H model is established. The reversal techniques are used to calibrate the parallelism errors, arm lengths and zero position of the AACMM. The effects of the bending and torsion deformations caused by the gravity of the arms are removed. The experiments prove that the calibration method is simple and the measurement expanded uncertainty (_2uc$2_{u_c}$) of the developed AACMM with a measuring range of (∅200–∅1000 mm) × 250 mm is less than 10 μm after error compensation.     

A traceable technique to calibrate dc current shunts and resistors in the range from 10 μΩ to 10 mΩ

A traceable to dc resistance and dc voltage National Standards measurement technique to calibrate dc current shunts and resistors in the range from 10 μΩ to 10 mΩ has been developed at National Institute of Metrological Research (INRIM) in addition to the primary reference system for low value resistors calibration. This technique is applicable in secondary and industrial metrological laboratories. It is based on a volt-amperometric method, to compare an unknown shunt with a standard one in 1:1 or 1:10 ratios. In the setup are involved: a dc current calibrator and a current generator to supply currents respectively up to 100 A and up to 1200 A, with a switch to reverse the current, two 7 1/2 digit nanovoltmeters (nVs) for the acquisition of the voltage on the standard and under calibration shunts and two Tinsley 100 μΩ and 1 mΩ standard shunts kept in mineral oil and with a cooling system. An optional variation in the procedure that can reduce the measurement uncertainties is discussed. The 2σ relative capabilities of the technique span from 6.0 × 10⁻⁶to 4.6 × 10⁻⁴. Compatibility results with the INRIM reference measurement system for low value resistors calibration are also given.     

Machining accuracy improvement for a dual-spindle ultra-precision drum roll lathe based on geometric error analysis and calibration

This paper performs a comprehensive analysis and calibration on the geometric error of the ultra-precision drum roll lathe with dual-spindle symmetrical structure and cross slider layout. Firstly, the volumetric error model which contains all geometric errors of the dual-spindle ultra-precision drum roll lathe (DSUPDRL) is developed based on the combination of the homogenous transfer matrix (HTM) and multi-body system (MBS) theory. Secondly, sensitivity analysis for the volumetric error model is conducted to identify the sensitive geometric error components of the DSUPDRL using an improved Sobol method based on the quasi-Monte Carlo algorithm. The result of sensitivity analysis laid the foundation for the subsequent geometric error calibration. Then, some sensitive error components along the X and Z directions are calibrated using a laser interferometer and a pair of inductance displacement probes. Besides the volumetric error model, the concentricity error caused by dual-spindle symmetrical structure is proposed and calibrated by the on-machine measurement using a classic reversal method. Finally, a large-scale roller mold with a diameter of 250 mm and a length of 600 mm is machined using the DSUPDRL after calibration. The experimental result shows that 1.4 μm/600 mm generatrix accuracy is obtained, which validate the effectiveness of the geometric error analysis and calibration.     

A novel approach for realization of primary vibration calibration standard by homodyne laser interferometer in frequency range of 0.1 Hz to 20 kHz

The paper discusses the primary vibration calibration standard of NPL, India capable of calibrating the reference accelerometers in frequency range from 0.1 Hz to 20 kHz as per ISO 16063-11. The excitation subsystem produces constant vibration at a specified amplitude and frequency, while the measurement system uses NI interface for measuring the quadrature output. The acceleration level and voltage level at the calibration frequency f is determined by applying a Discrete Fourier Transform to the voltage and displacement signals, and then examining the spectral component at frequency f. A PC-based data acquisition system acquires the accelerometer voltage signal and analog quadrature interferometer photodetector signal pair as well as a digital quadrature pair whereby the software processes the demodulated photodetector signals to reconstruct the armature displacement. The validation of the calibration results for standard reference accelerometers with manufacturer results and uncertainty in calibration in entire frequency range 0.1 Hz to 20 kHz is reported in the present work.     

Uncertainty contribution of tip-sample angle to AFM lateral measurements

AFM measurements are very important for quality control in the photovoltaic, microfluidic, electronic or micro-optic industries. This work proposes an algorithm to complete the uncertainty evaluation of AFM systems along the XY-axis under conditions where tolerance of curved surfaces must be controlled. This algorithm is also tested for tilt angles between tip and sample from 0° to 9° using an experimental arrangement which consists of an AFM instrumented with an inclinometer and four step height standards.Results show good agreement between the theoretical model and experimental results for samples with larger steps TGZ03 (465 nm) and TGZ11 (1416 nm), but with poor results for the smaller samples TGZ01 (17.6 nm) and TGZ02 (73.1 nm). An angle of 9° shows an error of about 3% in the horizontal determination of the step dimension, but it could increase to 47% for a tilt angle of 30° according to the theoretical model.The angle error between tip and sample is included in the uncertainty budget using a uniform distribution. An evaluation is performed in a theoretical rolling machine for imprint lithography where a step must be measured with nominal dimensions of 3 μm—X-axis and 1 μm—Z-axis. An assumed tip-sample angle is assumed that changes from 0° to 22.5° (curved form) and produces an uncertainty contribution to the X measurement of 55.7 nm. This uncertainty is important and must be considered to guarantee tolerances in quality control of curved form products.     

十字形磁梯度张量系统的误差校正

针对十字形磁梯度张量系统中的单磁力仪误差(三轴灵敏度偏差、非正交误差和零点漂移误差)以及磁力仪之间存在的不对正误差,提出了十字形磁梯度张量系统的误差校正方法。首先,建立单磁力仪误差模型,采用基于椭球约束的最小二乘拟合算法对磁力仪的测量数据进行拟合从而得到椭球拟合参数;然后,接着利用Cholesky分解得到单磁力仪误差校正矩阵;最后在单磁力仪误差校正的基础上,利用正交Procrustes方法对不同磁力仪间的测量数据进行拟合从而得到磁力仪间的不对正误差校正矩阵。对提出的方法进行仿真与实测实验验证,实验结果表明:经过校正,磁梯度张量各分量的最大波动量由10 049nT/m降到52nT/m。提出的校正方法可以基本消除十字形磁梯度张量系统的误差,提高测量结果的准确度,且方法操作简单,不需要高精度的三轴无磁转台等设备,具有较高的实用价值。     

Vibration effect on hardness measurement

In this paper, the effect of ground vibration on hardness measurement, Rockwell scale C hardness, Vickers scale HV1 hardness and Leeb hardness is studied. The hardness machines were placed on the vibration table. The vibration signal is single frequency sinusoidal wave, which frequency and amplitude of vibration can be controlled. The hardness value at free from vibration state is used as a reference to calculate the error of each hardness measurement at certain frequency and amplitude. Two Rockwell hardness testing machines are used to measure hardness blocks: 20, 40, and 60 HRC. Both machines give the same tendency. Significant negative errors occur around frequency 5–15 Hz. Moreover, ground vibration has more impact on the soft range of hardness than hard range. The result from this paper can be used as guideline for laboratory to control environmental vibration amplitude to be less than 0.01 m/s² for frequency (10 ± 5) Hz and 0.05 m/s² for other in Rockwell scale C hardness measurement. Effect of vibration on Vickers and Leeb hardness measurement is preliminarily studied. Results on 200 HV1 and 900 HV1 measurement show that vibration creates peak of error at frequency 20 Hz of amplitude more than 0.01 m/s² and the effect can be observable at all frequency for amplitude of 0.04 m/s². Different from Rockwell and Vickers, Leeb hardness measurement is not influenced by vibration in this experiment.     

The geometric dynamic errors of CMMs in fast scanning-probing

Quasi-stiffness model is effective for the compensation of the geometric errors of coordinates measuring machines (CMMs) in slow probing, but degrade the error compensation accuracy due to the generation of dynamic errors in fast probing. It is usually regarded that acceleration is the major origin of dynamic errors; and yet the dynamic effects that rise from the quick fluctuation of geometric errors in fast probing had attracted little attentions. This paper presents a model for the dynamic effects of the geometric errors of CMMs in fast probing, and investigates their properties with experiments. The error model is built with recursive least squares (RLS) identification technique by taking probing acceleration and the 6 geometric errors of X slideway for the inputs while the positioning error of probe tip for output. Then the positioning error of probe tip is decomposed into 7 components corresponding to the 7 inputs. Analyses on the experiments show that the angular errors around Y and Z axes, ε_Y(x) and ε_Z(x), can induce remarkable dynamic effects, especially in a CMM with low stiffness air bearing. Error compensation with RLS identification seems feasible theoretically, but it is not recommendable due to the veracity uncertainty of identification. Nevertheless smoothening the sharp corners of the curves of geometric errors, especially ε_Y ∼ x and ε_Z ∼ x, in terms of probing speed and Y coordinates of probe tip is considered as a simple but effective and reliable method to improve the accuracy of CMMs errors compensation in fast probing.     

A system for gas sensing employing correlation spectroscopy and wavelength modulation techniques with a multimode diode laser

A tunable multi-mode diode laser system based on correlation spectroscopy and wavelength modulation spectroscopy (TMDL–COSPEC–WMS) is designed and demonstrated for the concentration measurements of oxygen using A-band absorption lines of oxygen around 760 nm. The O₂ concentrations are conversed from the relation between the normalized WMS-2f signal peak heights of the measurement and reference signals which selected based on high signal to noise ratio and correlation coefficient. The correlation and the fitted slope between the measured and actual O₂ concentration are 0.9987 and of 1.025 ± 0.012 respectively over the tested range, which indicate the high linearity and accuracy of the system. A sensitivity of 350 ppm m is approved using 30 successive measurements with each measurement time taking ∼20 s during 30 min. A continuous measurement for oxygen in ambient air during approximately 200 min confirms the stability and the capability of the system.     

“Magic size” effect in the packing of n-alkanes on Au(1 1 1): evidence of lowered sliding force for molecules with specific length

Molecular structure of monolayers formed at the interface between Au(1 1 1) surfaces and solutions containing n-alkanes has been studied by in situ scanning tunneling microscopy at room temperature. Increasing the C_nH_2n+2 length from n=10 up to 50 with even n numbers alternates rectangular and tilted arrangement of alkanes within the self-organized layers. This alternation is related to the dramatically lowered sliding force for molecules with a length close to mT (m-integer), where T is the period of commensurability between the CH₂-CH₂-CH₂ period along alkyl chains and the interatomic distance along Au〈1 1 0〉 direction.     

Combined measurements – A way to improve the measurement accuracy of an additive quantity

We show a way to take measurements of an additive quantity on several objects that gives the possibility to get considerably better accuracy of results than that one can get when the measurements are performed on particular objects one by one, when the same instrument is used in both cases. The theory of such measurements is described and the possible gain in accuracy derived. When n = 4–6 objects are to be measured, the uncertainty of combined measurement can be lowered by better than 2–4 times, respectively. Theoretical predictions were found to agree with both real and computer simulated measurements.     

An experimental intercomparison of gas meter calibrations

This paper presents four calibrations carried out in four different, independent, metrological accredited laboratories, on six diaphragm gas meters for domestic use (G4). The aim of this study is to evaluate the degree of metrological agreement among different calibration results, by means of the assessment of suitable factors (compatibility index, also known as normalized error). This application study is quite interesting in the field of “legal metrology”, when often conformity assessment are requested in order to assure the adequate behavior of a domestic gas meter. The six gas meters were calibrated in four different laboratories, each of them characterized by different values of the calibration uncertainty (also called CMC = Calibration and Measurement Capability, or BMC = Best Measurement Capability, or Minimum Uncertainty). Two alternative approaches about the metrological compatibility are introduced: a quantitative approach and a qualitative approach. The calibration results show that for diaphragm gas meters for domestic use, the metrological agreement should be preferable by means of the qualitative approach.     

Passive control of circular cylinder wake in shallow flow

The control of vortex shedding of a circular cylinder in shallow water using a splitter plate located in the downstream of the circular cylinder was studied by employing particle image velocimetry (PIV) technique. Experiments were carried out in a water channel having a test section of 8000 mm × 1000 mm × 750 mm dimensions at a Reynolds number of 6250. The length of the splitter plate (L) was varied within the range of 0.5 ? L/D ? 2 with an increment of 0.5. The plate was submerged into water at different height ratios (h_p/h_w) such as 0.25, 0.5, 0.75 and 1.0. Mean velocity vector field, corresponding vorticity contours, streamline topologies and turbulent quantities were calculated using 300 instantaneous velocity vector field measured by PIV. As the ratio of h_p/h_w increases, the effect of the splitter plate on the suppression of the vortex shedding increases. Flow characteristics and examination of spectra indicate that Karman vortex shedding is attenuated pronouncedly for the cases of L/D ? 1 and h_p/h_w ? 0.75. The transverse Reynolds normal stress is more effective on the attenuation of turbulent kinetic energy than the streamwise Reynolds normal stress. The value of peak transverse Reynolds normal stress is reduced to 90% of that of the bare cylinder at most.