Conversion of Fluid Thermal Parameters into Frequency and Time by Means of Thermistors

A versatile direct converter of fluid thermal parameters into frequency and time is described. The circuit is based on a complementary multivibrator, the frequency of which is controlled by the temperature-sensitive current generator. Temperature-to-time (?-T) and temperature-to-frequency (?-f) conversion is obtained by simple rearranging of passive circuit elements. The linearizing conditions and sensitivity for various probe configurations are given. In battery telemetering systems, the circuit is economical in power supply consumption due to the very small mark-to-space ratio of output pulses. The sensitivity as well as the transducer Rmax/Rmin ratio are considerably increased in comparison with other direct thermistor converters. With the positive temperature coefficient (PTC) thermistor probe, the frequency change can be about three decades in the temperature range of 30°C, which represents the highest obtained sensitivity of ?-T/f converters. The circuit is also successfully applied with self-heated miniature bead thermistors as a sensor when it represents the linearized air speed-to-time converter within the range of 0-3.6 m/s.     

Broadband millimetre-wave passive spatial combiner based on coaxial waveguide

A broadband millimetre-wave passive spatial combiner using a microstrip probe array and an oversized coaxial waveguide is successfully designed and tested. The equivalent circuit approach of transverse electromagnetic (TEM) lines is adopted to synthesise the coaxial stepped impedance transformer from a K connector with the oversized coaxial waveguide and to analyse the microstrip probe array. The equivalent susceptances of the step discontinuities for the power divider are calculated. A four-way coaxial waveguide passive power combining circuit operating at the entire Ka-band is designed, fabricated and measured. Experiments on the four-way passive combiner show that a minimum insertion loss of 0.7 dB has been achieved at about 29.5 GHz. The combiner has shown a bandwidth of 26.5?40 GHz with 10 dB return loss and less than 2.5 dB insertion loss.     

一种电感式位移传感器的电路系统设计

介绍了一种电感式位移传感器的电路系统.该系统以一片AD698芯片为信号调整电路的核心,将位移量输出信号转换为相应的直流电压值,并结合其它一系列电路模块实现了测头位移量测量.通过对测头的标定试验证明该系统精度高、线性测量范围大.     

Plasma characterization in sputtering processes using the Langmuir probe technique

The Langmuir probe technique, which has long been used in the field of plasma physics, can be a very powerful tool in characterizing the sputtering process. In this context, theoretical formalism, design requirements and the experimental procedures necessary for the application of this technique to both r.f. and d.c. sputtering are presented. It is shown that the plasma parameters can be determined in a simple way only if the probe operation is in the orbital motion limited regime. This condition is fulfilled for a cylindrical probe when the ratio of the probe radius to the Debye length of the plasma is less than 3. In the case of r.f. discharges erroneous data are obtained if a large r.f. current is flowing to the probe. This current can be blocked by a suitable LC circuit. Using the Langmuir probe technique the variations in the plasma parameters in d.c./r.f. sputtering discharges as a function of target voltage/power and argon pressure are determined.     

Bridge Circuit for Measuring Differences of Current or Voltage from a Preselected Value

A bridge circuit has been developed, using a Zener diode, which enables measurement of small changes in current or voltage from a preselected value. The circuit features increased sensitivity over a meter whose range includes the total current and is more easily used than a balanced bridge or potentiometer. The design equations are developed and the design procedure outlined for both the current and voltage difference measuring bridges, while a sample calculation is made for the current change measuring circuit. A bridge similar to that in the sample calculation was built and tested. The test circuit displayed less than 1 per cent nonlinearity of meter current vs change of input current for the design region of 460±5 ma. This shift was attributed to a slight heating of the Zener diode or a resistor at the higher test currents, but since the diode used in the test circuit had a smaller power rating than the type originally intended for use, it is not considered to be a serious limitation.     

小型自感应原子力显微镜测头及其标定

设计了一种小型轻敲式自感应原子力显微镜(AFM)测头以实现微/纳尺度下的几何量测量.轻敲式测头采用石英音叉式自感应探针,通过自身的电信号输出检测悬臂梁的振幅变化,无需额外的光学传感器.设计了测头的微弱自感应信号放大电路,并补偿音叉寄生电容对测量的干扰.机械结构紧凑便于将测头固定于光学显微镜下观察测量情况,同时屏蔽外界的干扰.利用显微激光多普勒测振系统,标定了测头机电耦合系数为145 nm/V,由此可以计算测头工作频率下悬臂梁的振幅.搭建了以纳米测量机(NMM)为高精度定位平台的测试系统,利用该系统对测头进行进/退针实验,标定测头的灵敏度为0.47 nm/mV,NMM内置的干涉仪保证标定直接溯源至"米"定义.实验表明测头的非线性误差小于1%,测量范围在百纳米级.     

Improved equivalent circuits for complementary split-ring resonator-based high-pass filter with C-shaped couplings

The authors modify the complementary split-ring resonator (CSRR) with dual C-shaped couplings for high-pass filter (HPF) design and propose improved equivalent circuits as a means to analyse the filter. The p-type circuit of the dual C-shaped coupling in the CSRR-based HPF is presented to have the improved equivalent circuit in contrast to the conventional equivalent circuit. At 3 dB, the cut-off frequency f _{? 1.74 GHz, the maximum IL is within 0.33 dB up to 8 GHz and the 65.81 dB rejection extends down to 0.53 GHz. Simulation and measurement results including surface current distributions and frequency responses are presented and discussed.}     

Analog Linear-Scale Ohmmeter

This paper describes a new solid state circuit for resistance measurement in the range 1-108 ?. The advantages of this circuit include: reliability, simplicity of design and use, low cost, and the fact that resistance scale is linear. The accuracy of measurement is around ±2 percent of reading at full-scale value in the range 1-106 ? and ±6 percent of reading at 10 M? and 100 Mg. This circuit is temperature-compensated and exhibits good operational stability. The constructional cost of the instrument is about $41.00.     

Effects of externally-generated electrons on pressure measurements of inverted magnetron gauges at Diamond

Diamond Light Source (Diamond) utilises a large number of Inverted Magnetron Gauges (IMGs) for both monitoring the vacuum and as a source of interlocks for protection of the machine. During storage ring operation it has been found that, in the presence of the stored electron beam, charged particles, assumed to be electrons, impinging on some of the gauges cause the pressures indicated by the gauges to drop to zero which causes problems with the operation of the storage ring. Diamond has designed and fitted a magnetic filter at the neck of each affected gauge port to eliminate this problem. This paper reports on and discusses experiments and proposed experiments with an electron flood gun and IMGs from two different manufacturers (MKS Instruments and Pfeiffer Vacuum) aimed at obtaining a better understanding of the effect. Externally-generated electrons from the flood gun can cause serious errors in the pressures indicated by the gauges; the error can be positive or negative depending on the gauge current-measuring circuit. Methods aimed at eliminating these spurious pressure readings, such as magnetic filters, bias voltages within the gauges and the use of earth meshes and baffles are also discussed.     

Photovoltaic response of a topotaxially formed CdS-Cu(x)S single nanorod heterojunction

In the present study, a combination of a hydrothermal route and a topotaxial conversion reaction has been used to grow a cadmium sulfide-copper sulfide (CdS-Cu(x)S) single nanorod heterojunction. The J-V characteristics of the CdS nanorods show Shockley behaviour consistent with the energy band diagram of the platinum conducting atomic force microscope (CAFM) probe-CdS nanorod combination. The photovoltaic response measured on the CdS-Cu(x)S nanorods using a CAFM probe shows the formation of a heterojunction with an open circuit voltage of 320 mV, a short circuit current density of 5.5 mA cm?2 and a crossover of dark and light J-V curves related to the photoconductivity of the interfacial CdS layer. The lengthwise heterojunction fabricated in the present study has many potential advantages in comparison to other single nanorod junctions.     

AC–DC Transfer Standard Measurements and Generalized Compensation With the AC Josephson Voltage Standard

We present AC-DC transfer standard measurements using the National Institute of Standards and Technology's pulse-driven AC Josephson voltage standard source. We have investigated the frequency dependence for several output voltages up to 200 mV for frequencies from 2.5 to 100 kHz. We found that, as the frequency increases, the ac-dc differences for the two arrays on the same chip do not agree. We explored this deviation in ac-dc difference for the two arrays by investigating different configurations of the probe cabling and wiring, chip carriers, and on-chip circuit design. We found that the circuit design produced the greatest improvement, particularly at the highest frequency (100 kHz), where the deviation in ac-dc difference was reduced by more than 60%. In this paper, we also demonstrate tenfold higher output voltages and improved operating margins for arbitrary (nonsinusoidal) waveforms. These enhancements were accomplished by implementing a more general current bias to the arrays having the same harmonic content as that of the synthesized arbitrary waveform.     

In-Circuit Impedance Measurement Using Current Sensing

A novel approach to in-circuit measurement of resistors, capacitors, and inductors was evolved. This approach utilizes current sensing, making possible the measurement of in-circuit components which may be directly shunted by impedances as much as two to three orders of magnitude lower in impedance than the unknown. A minature clip-on probe was developed to facilitate measurements of components mounted on printed circuit boards. A compact impedance comparator was constructed which measured in-circuit components within approximately 2 to 4-percent accuracy over the following ranges: for resistance, 1.5 ? to 1 M?; for capacitance, 100 pF to 60 ?F; and for inductance, 400 ?H to 60 H. Impedances as low as one to three orders of magnitude smaller than the measured element impedance, depending on the probe used, shunted the unknown when the stated accuracy was measured. Much of the quoted inaccuracy is due to the ±3-percent resistance and ±0.1-percent linearity tolerances of the reference resistor which was used for all measurements.     

无源多通道神经硅微电极的设计方法

为了探讨一种用于神经信号测量的无源多通道硅微电极的设计方法,基于电极的结构和制造工艺,提出了硅微电极用于测量神经信号的电路模型．从大脑皮层及脑膜的结构、互连线的干扰噪声和探针的机械特性3个方面讨论了神经微电极探针的几何参数确定方法,并提出了在满足一定负载能力以穿透硬度较大的脑膜的前提下,尽量减小探针体积的设计原则．     

Investigation of a double shrouded probe for particle sampling in high velocity airflows

An accurate forecast of the concentration of fine dust in the atmosphere is critical because of the negative public health impacts associated with high concentrations of particulate matter. To achieve an accurate forecast, large volumes of data need to be collected over a wide range of regions to act as forecast model boundary conditions. Therefore, the concentration of fine particles should be measured at both fixed observatories and from a range of moving monitoring stations, including cars, trains, and aviation vehicles. To accurately record particulate concentrations at flow velocities up to 200?km?h^?1, this study proposed a double-shrouded probe design based on the widely used single-shrouded probe. Using the double-shrouded probe, isokinetic sampling for PM_2.5 was achieved at velocities up to 200?km?h^?1, and for PM₁₀ at velocities up to 75?km?h^?1. When flow velocities exceeded these values and particle sizes increased, particulate concentrations were overestimated. However, as compared to the single-shrouded probe, the double-shrouded probe reduced the level of overestimation markedly.     

A nanoscanning platform for bio-engineering: an in-plane probe with switchable stiffness

Scanning probe microscopy (SPM) has been one of the most important tools to image and, hopefully, to manipulate bio-structures at micro/nanoscales. However, the current out-of-plane cantilever design makes it very difficult to extend the spectrum of the current SPM technology to meet many new functionalities arising from bio-engineering applications. An in-plane scanning probe concept is developed to accommodate the new functional requirements. It is designed to have a single-strand multi-walled carbon nanotube (CNT) tip assembled at the end of the probe, a built-in actuator and a tip deflection sensor, all in the same plane. The coplanar design is compatible with most of the standard MEMS processes and would facilitate the assembly of a carbon nanotube tip to the micromachined probe. The in-plane design features a switchable stiffness which adapts the scanning probe's stiffness to the changing surface hardness of the sample. This paper describes how the variable stiffness is accomplished by engaging or disengaging electrostatically actuated clutches, in addition to the discussions on many possible benefits of the in-plane scanning platform.     

A method of measuring electrode temperature for arc powercalculation

A technique for the construction of the thermocouple probe used for the measurement of electrode temperature under the influence of arcing in a low-power circuit breaker at break is reported. The problem of appreciable heat diffusion to the surroundings during the short time of arcing at break, typically 3-6 ms (depending on the speed of break), is dealt with by placing the thermocouple probe as near as possible to the electrode's surface, and in the center where, in most cases, the arc occurs. Under dc test conditions the amounts of the are power received by each electrode for various parameters such as current and electrode spacing are calculated     

Current Mode Monolithic Active Pixel Sensor With Correlated Double Sampling forCharged Particle Detection

A monolithic active pixel sensor operating in current mode for charged particle detection is described. The sensing element in each pixel is an n-well/p-sub diode with a PMOS transistor integrated in an n-well. The drop of the n-well potential from the collection of charge modulates the transistor channel current. Each pixel features two current mode memory cells. The subtraction of distant-in-time samples frees the signal of fixed pattern noise (FPN) and of the correlated low-frequency temporal noise components, resulting in extraction of the particle footprint. The subtraction circuits are placed at each column end. A transimpedance amplifier, integrating in sequence two current samples and subtracting the results in an arithmetic operation, was adopted. The integrated version of the transimpedance amplifier, designed with a maximized conversion gain, is burdened by a risk of an early saturation, imperiling its operation, if the dispersions of the dc current component are too big. The degree of dispersions could not be estimated during the design. Some number of columns is available as a backup with the direct current readout. An external realization of the subtracting circuit, based on the same principle, is used to process direct output columns. The concept of the data acquisition setup developed, the tested performance of an array of cells, and the processing circuitry are described     

An Automatic Digital Q-Meter: New Approach to the Digital Measurement of Magnification Factor

Few procedures, known so far, for the design of a digital Q-meter, were based on the ratio between the reactive and the nonreactive components of measured circuit elements or on the determination of the corresponding logarithmic decrement in that circuit. In the first procedure, the ratio of two voltages, proportional to the above mentioned components, has to be found and numerically displayed, when the same current passes through these components. This procedure is limited to relatively low frequencies and hence to small values of a Q-factor. In the second procedure, the number of damped oscillations in the circuit with the tested elements, which occur in the time interval between the initial amplitude of a suddenly injected signal and the damped amplitude e? time smaller than the first one, corresponds to the numerical value of the Q-factor. The new procedure, presented in this paper, results in the numerical display of the Q-factor of an oscillatory circuit (or of its self-inductive element) at a relatively high resonant frequency. The procedure is based on the determination and numerical display of the ratio between the overvoltage, created by the resonance, and the high-frequency voltage injected in the oscillatory circuit. During the sweeping of the frequency-modulated injection signal around the proposed resonant frequency, the differentiation of the corresponding resonance curve is made; the passage of the differentiated signal through the zero value is marked by an appropriate comparator circuit.     

Expanded quantum cryptographic entangling probe

A generalized quantum circuit and design are given for an optimal entangling probe to be used in attacking the BB84 protocol of quantum key distribution and yielding maximum information to the probe. Probe photon polarization states become optimally entangled with the BB84 signal states on their way between the legitimate transmitter and receiver. The present design generalizes an earlier one by Brandt [J. Mod. Optics 52 2177 (2005)] to include a complete range of error rates that can be induced by the probe.     

0.18-microm complementary metal-oxide semiconductor push-pull vertical-cavity surface-emitting laser driver operating at 2.5 Gb/s with symmetric rising and falling edges

A vertical-cavity surface-emitting laser (VCSEL) driver design that utilizes a novel push-pull circuit topology is described. The VCSEL driver design can provide both a current pushing and a current pulling mechanism and therefore is capable of producing symmetric rise and fall times. The design was implemented in a 0.18-microm foundry n-well complementary metal-oxide semiconductor technology and operates at data rates up to 2.5 Gb/s with a power consumption of 45 mW at an average optical output power of 1 mW.