A compact self-shielding prober for accurate measurement ofon-wafer electron devices

A compact self-shielding prober is proposed for measuring low-current-voltage characteristics of on-wafer electron devices. In the prober, a wafer and a wafer stage are set in a very small shielded region mostly enclosed by a plane top-board, a wafer-stage shield, and a sidewall shielding ring. A current of less than a picoampere can easily be measured without any shielding box. A prober designed to observe all devices on 4-in wafers can be as small as 27 cm×27 cm×12 cm. High-speed input/output waveforms of on-wafer large scale integrated circuits (LSIs) observed with this prober are as clear as those of packaged LSIs observed directly     

Digital self-calibration method for MEMS sensors

This paper presents a digital self-calibration method for microelectromechanical systems (MEMS) using a relay-feedback loop and a set of discrete-time filters. This method is based on the measurement of limit-cycles at the comparator's output, which result from a synchronization phenomenon between the natural frequency of the MEMS and the clock frequency of the discrete-time components. We show how quantized information concerning the MEMS parameters may be extracted from the shape of the limit-cycle, which depends on the characteristics of the MEMS (pulsation, damping, etc.). This digital technique is amplitude-independent, relatively insensitive to noise, and not costly to implement. Details concerning its implementation are discussed, and some simulation and experimental results are given.     

Camera self-calibration method suitable for variant camera constraints

This paper presents a self-calibration algorithm that seeks the camera intrinsic parameters to minimize the sum of squared distances between the measured and reprojected image points. By exploiting the constraints provided by the fundamental matrices, the function to be minimized can be directly reduced to a function of the camera intrinsic parameters; thus variant camera constraints such as fixed or varying focal lengths can be easily imposed by controlling the parameters of the resulting function. We employed the simplex method to minimize the resulting function and tested the proposed algorithm on some simulated and real data. The experimental results demonstrate that our algorithm performs well for variant camera constraints and for two-view and multiple-view cases.     

Planning measurements in certifying methods of performing measurements

A procedure is proposed for planning measurements in certifying a linear measurement method MM, and estimates are made of the adequacy of a linear MM. Translated from Izmeritel’naya Tekhnika, No. 1, pp. 60–69, January, 1998.     

LRR-a self-calibration technique for the calibration of vector network analyzers

A new self-calibration procedure, the LRR method, for the calibration of vector network analyzers is presented. The calibration circuits consist of partly unknown standards, where L symbolizes a line element and R represents a symmetrical reflection standard. In contrast to the thru reflect line (TRL) method, which needs a line-standard with a different length than the other calibration standards, the calibration circuits of the LRR method are all of equal mechanical length. This is advantageous because the connectors of the vector network analyzer do not, thus, have to be placed at different distances from each other during calibration. In addition, the complexity of the test fixture can be reduced. The robust functionality of the LRR method is confirmed by measurements.     

A new self-calibration method for electronic current transformers

Compared with traditional current transformers (CTs), electronic current transformers (ECT) have the following advantages: (1) no saturation problem, (2) wider measurement range, (3) smaller footprint, (4) lighter weight, and (5) easier for digitization. Hence, the ECT is one of the critical components in the development of intelligent substations. Since the majority of the sensing elements of ECTs are semiconductor materials, their accuracy and sensitivity are influenced by the ambient temperature. Moreover, the quiescent output voltage of the semiconductor-based ECT is also affected by the ambient temperature. This paper proposes a self-calibration method with the ability of quiescent-output-voltage compensation and sensitivity compensation. The proposed design can automatically adjust the quiescent output voltage and the sensitivity variation when the temperature changes. The experimental test results demonstrate that an ECT with the proposed self-calibration method can achieve Class 0.5 for measuring CTs and Class 5P20 for protective CTs.     

Recent advances in optical methods for thermal expansion measurements

Progress in optical instrumentation for thermal expansion in the 1980s is reported. These instruments present some common features: (1) they are designed to operate at high temperatures; (2) they use optoelectronic detection so they can be linked to automatic data acquisition systems; and (3) they provide high-rate data acquisition. Three instruments follow a geometrical approach (profile projector or location with a laser beam), while two other ones are interferometric.Invited paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

微操作机器人的显微视觉自标定方法

在分析微操作机器人结构特点的基础上确定了待标定参数,提出了一种基于显微视觉的自标定方法。通过动态跟踪随机器人运动的目标来计算其图像坐标,采用最小二乘法拟合目标运动轨迹在显微镜坐标平面中的投影直线,并结合高精度机器人的位移量,经过几何投影和变换,标定出待标定坐标到显微镜坐标的转换矩阵。该标定方法无需特殊辅助测量仪器。实验表明,角度标定重复性好,位置标定误差小于 2 个像素。     

A learning algorithm for self-calibration of a voltage calibrator

An algorithm either to extend the calibration period or to reduce the measurement uncertainty of a DC voltage reference module is presented. This module is used either as a transfer, independent, or working standard, or as a reference module incorporated into a larger measuring system. The basic idea is that the deviation history of measured voltage differences of reference elements of a group reference module during the calibration period can be used as a learning period for a neural network. This neural network, when created, can numerically correct particular reference elements later in the working period. Results were obtained by simulation and evaluated on the basis of empirical data and simulated input functions. Hardware solutions to model this algorithm are discussed     

Interframe intensity correlation matrix for self-calibration in phase-shifting interferometry

A new method of estimating reference phase shifts in phase-shifting interferometry is proposed. The reference phase shifts are determined from a matrix that represents the interframe intensity correlation (IIC) of phase-shifted interferograms. The root-mean-square error of intensity measurement is automatically obtained from the smallest eigenvalue of the IIC matrix. The proposed method requires only four interferograms, unlike others, and can extract phase shifts reliably even from interferograms without well-defined fringes, such as speckle patterns. In typical conditions, reference phase shifts and wave-front phases can be determined with an accuracy of lambda/6310 and lambda/150, respectively. The validity of the method is tested by comparing it with other methods in experiments and simulations.     

Instrumentation and methods for low temperature measurements in high magnetic fields

There are several difficulties associated with the accurate measurement of low temperature in the presence of an intense magnetic field B. Most of the problems stem from the direct effect of the field on the thermometric properties of almost all of the comcommonly used sensors. Because the magnitude of the field effect, eg magnetoresistance, varies widely as a function of B, T, and the thermometer itself, a careful selection process is necessary to minimize the error. As an aid to such a process, a detailed comparison is presented of the field-dependent errors, Δ/T, as a function of T, of carbon, carbon-glass, germanium, and platinum resistance thermometers, thermistors, Si and GaAs diodes, thermocouples, capacitance thermometers, and several other less popular devices. Specific recommendations are made on the basis of the comparison. The related problem of magnetic field measurement is also examined, with emphasis on the recent characterizations of commercially available InAs, InSb, and GaAs Hall effect probes. From the results of measurements over the 1.5–300 K range and to fields as high as 23 T, several encouraging conclusions may be drawn concerning the performance of the sensors as magnetometers in the 1% accuracy range.     

A digital self-calibration circuit for absolute optical rotary encoder microsystems

The parameters of the analog waveforms produced by the front-end electronics of absolute optical rotary encoders are affected by substantial differences and drifts. The threshold level required to convert the generated analog signal into a digital square wave in each read-out channel has to, therefore, be calibrated so as to keep the output duty-cycle close to its ideal value of 50%. This paper presents a digital self-calibration circuit specifically designed for this purpose. The circuit performs dynamic calculation of the threshold level, continuously compensating for encoder nonidealities while the system is normally operating. This avoids the need for manual calibration, provides thermal stabilization, and prevents performance degradation. The proposed digital calibration system was integrated in conventional CMOS technology and was then successfully evaluated.