一种使用矢量网络分析仪的阻抗测量改进方法

基于反射法理论提出了一种使用矢量网络分析仪测量集总参数元件阻抗的方法,引入阻抗匹配电路,拓宽了矢量网络分析仪的阻抗测量范围.通过对匹配电路二端口网络模型中参量A的分析,给出相应的被测元件的阻抗计算式,消除了夹具对测量结果的影响.采用矢量网络分析仪直接测量法和该阻抗测量法分别测量了5种不同阻值的金属膜电阻,结果表明,该阻抗测量方法的测量精度高于矢量网络分析仪直接测量的精度,可在30 kHz～100 MHz频率范围内实现几欧至千欧阻抗的精确测量.     

小电阻对测量结果的影响

电阻是电路的基本物理参数,电阻很小时,分析计算常忽略不计.但在许多场合下如果忽略电路中存在的小电阻,将会带来测量结果的不准确,此时必须消除小电阻影响.文中介绍了几种不同测量环境下微小电阻对测量结果的影响及消除方法.     

测量电阻法、测量波形法在电子仪器修理中的应用

一、测量电阻法用三用表的电阻档来检查电子仪器电路中的元器件和有关电路的对地电阻,是查找仪器故障的有效方法之一。对电路中的虚焊、电位器滑动接点接触不良以及电感线圈等的断路或短路故障,通过这种方法也能发现。对接触电阻或通路电阻的测量,应使用三用表中电阻档     

电阻网络对光电检测电路直流偏置的抑制作用

为了对微弱光信号进行提取,设计了具有100dB通频带增益的跨阻放大电路,并针对一般光电检测电路存在的直流偏置现象进行了分析研究,提出了利用T形电阻网络代替孤立反馈电阻的新型电路结构。利用Pspice软件对电路进行了仿真,结果表明引入T形反馈电阻网络在抑制光电检测电路直流偏置方面具有显著的效果。     

基于比率法的高精度电桥电路及其应用

提出一种基于比率法的高精度电桥电路,用于测量电阻传感器中的高精度电阻。该电桥电路是基于模数转换器的数字量输出,采用模拟输入电压与参考电压比率的方法,将电桥的不平衡输出经放大后作为模数转换器的模拟量输入,将电阻式传感器相同一侧另一桥臂两端的电压差经放大后作为模数转换器的参考电压,经过模数转换后两者比率的数字量作为系统的输出。经过该电路处理后,电阻信号与系统的输出之间成线性关系,并克服了供电电压波动对电阻测量结果的影响,消除了系统的零点漂移和温度漂移。该电桥电路具有高准确度的电阻测量性能。     

万用表电阻测量电路的故障分析与调整

电阻测量电路的故障（以５００-Ｆ型万用表为例） ,往往是由于使用者的误操作造成的。常见故障、产生原因及消除方法见右表 :必须注意的是 ,在调整电阻测量电路时 ,一般应从Ｒ×１档开始 ,从低档到高档依次进行。无论是调整分流电阻还是限流电阻都要遵循多指增加 ,少指减少的原则。当电阻测量电路和直流电流的分流电路是公用的 ,调整时应保持直流电流档的原有误差不变。当电阻量程和直流电流的分流电路同为一个时 ,一般只调整限流电阻而不调整分流电阻 ,以免破坏直流电流档已调好的误差。当电阻量程的工作电流值不与任何直流量程同一时 ,只…     

长期测试中电阻应变仪测量电桥的几点改进

由于高速度、高精度、自动化、数字化以及多点测量的要求，以前广泛采用的以电阻平衡箱作为多点转换，附以电阻平衡电路和电容平衡电路存在许多问题，如电阻、电容调平非常困难，转换开关的接触电阻的影响，在需要对应变进行长期监测的试验中无法解决初始值问题等。本文通过对一般测量电桥的误差分析，提出了几点改进的方法和建议。     

电子电位差计的改量程计算

电子电位差计测量桥路的简化电路见下图。图中,R_(HB)为固定分流电阻R_B,滑线电阻R_H、量程电阻R_M[见图中(b)]的并联等效电阻,λR_(HB)为不工作区,调整量λ为0.03～0.05;E为测量电路稳压电源的供电电压,I_1、I_2分别为测量电路上、下支路电流;E_t为热电偶。国家统一设计的规定为:E=1V,I_=     

长期测试中电阻应变仪测量电桥的几点改进

由于高速度、精度、自动化、数字化以及多点测量的要求，以前广泛采用的以电阻箱作为多点转换，附以电阻平衡电路和电容平衡电路存在的许多问题，如电阻、电容调平非常困难，转换开关的接触电阻的影响，在需要对应变进行长期监测的试验中无法解决初始的问题等。本文通过对一般测量电桥的误差分析，提出了改进的方法和建议。     

电子电位差计测量桥路故障检查方法

电子电位差计采用电压补偿法来测量被测参数。测量电路由滤波单元、测量桥路单元、定电压单元、连接组件、大滑线电阻等部分组成 ,如下图 :测量电路原理图检查测量电路故障的方法除了细心观察电源支路、上下支路的接线有无松动或脱落 ,各电阻有否开路、短路和损坏等情况以外 ,还使用以下方法进行检查。一、电位差检查方法 :利用便携式直流电位差计检查测量桥路输出端的电位差是否正常 ,因在测量系统中接ＲＣ滤波器 ,总电阻高达６ｋΩ多 ,如将此电阻串入直流电位差计中会使检流计的灵敏度下降 ,所以检查仪表的测量桥路时 ,应将便携式电位差计…     

Highly productive sorting of resistors

Conclusions The above circuit was successfully used for mass-production sorting of plug-in resistors with nominal values from 10 to 9000 ohm used in a universal network model.Reference resistors of the sorted nominal values are incorporated in the circuit for the convenience of operation. The set is universal and can be used both for measuring resistors and for their sorting with high precision. The resistors are sorted at a rate not exceeding 3 sec per resistor. The circuit can be recommended for use in automatic sorting machines.     

The Accuracy of Series and Parallel Connections of Four-Terminal Resistors

The range and accuracy of resistance calibration can be increased by the use of series and parallel connections of four-terminal resistors. Low value resistors can be permanently connected in series and reconnected in parallel by using Hamon's1 technique to change resistance level without materially affecting resistance accuracy. The resistors are connected in parallel by attaching shorting bars to one terminal at each end of each resistor and attaching matched resistors in series with the other terminals. High accuracy can be attained even though lead and connection resistance are relatively high. The purpose of this paper is to provide a theoretical base and an error analysis to justify the use of the series-to-parallel transfer technique at low resistance levels. The analysis uses a four-terminal equivalent circuit suggested by Searle.2 The accuracy of series and parallel connections of groups of like resistors is investigated in terms of the equivalent circuit. Procedures are developed for determining the connection accuracy of a set of resistors in parallel or series.     

电流模精密整流电路

由电压型运算放大器组成的精密整流电路要严格地匹配电阻才能获得精密全波整流波形．本文给出一种具有CCⅡ电路特性由运算放大器AD844所构成的电流模精密整流电路．无需匹配电阻就可输出良好的精密全波整流波形．且具有输入电压范围大，频带宽等特点．     

发动机检测仪检定装置的示波灵敏度检定设计

本文介绍了发动机检测仪检定装置的示波灵敏度电路设计。该电路由锁相环芯片CD4 0 4 6、十进制计数器CD4 5 18、低通滤波器MAX2 93和一些电阻、电容构成。电路设计合理 ,实际使用效果好     

Multiple-arm bridges with variable-resistor balancing

The theoretical possibility of measuring an unlimited number of two-terminal network parameters with multiple-arm bridges is established. The bridges are balanced by variable resistors and fed by voltage pulses of complex shapes. The analysis of a bridge circuit is described as an example. Translated from Izmeritel'naya Tekhnika, No. 6, pp. 50–54, June, 1999.     

一种脉宽调制的高稳定连续可调直流电压源

介绍了一种以深埋齐纳电压基准元件LTZ1000A主电路为基础,结合脉宽调制技术实现的在0～10 V范围内连续可调的高稳定直流电压源。选用精密电阻并采用适当的保温与隔离措施,实现了电压基准主电路输出高稳定7 V电压,其短期稳定性达到1.7×10^-8。利用具有相同温度系数和阻值的精密电阻组成比例升压电阻网络,使输出10 V电压的短期稳定性为2.4×10^-8。同时利用脉宽调制并经DC-DC转换电路及滤波电路得到0～10 V的电压输出,短期稳定性可在10^-7量级左右。     

A simple resistance network for calibrating resistance bridges

This paper describes a simple, passive, low-cost resistance network, closely related to Hamon build-up resistors, that enables the calibration of dc and low-frequency ac resistance and conductance bridges. The network is configured so that the four component resistors can be connected to realize 35 distinct four-terminal resistances, all interrelated by the usual formulas for the series and parallel connections of resistors. Theoretical analysis and experimental results show that with due care in the design, the network can be readily constructed to achieve an accuracy of better than 1 μΩ for resistances of the order of 100 Ω (1:10⁸) for angular frequencies from dc to 10⁴ rad/s     

Derivation of an electronic equivalent of QHE devices

Models of quantum Hall effect (QHE) devices described by an equivalent circuit are used both to analyze measurement systems and to study QHE physics. Although the most widely used equivalent is the one proposed by Ricketts and Kemeny, various other circuits have been published to suit to different needs in QHE analysis, including a network with only resistors and unity-gain amplifiers. In the following we discuss a general approach to the analysis of the electrical behavior of QHE devices, and show that they can be classified as gyrators. Gyrators are nonreciprocal network elements whose properties are well known from the theory of electrical network. They can be regarded as generalized equivalents of Hall effect devices, thus setting a general framework for the study of the electrical behavior of QHE and the derivation of equivalent circuits. Through the application of this technique, an electronic circuit capable of simulating a QHE device with nonnull longitudinal resistance is derived     

Digitally programmable active-R square wave generator

A digitally programmable active-R square-wave generator circuit is discussed. The circuit uses only two operational amplifiers, two operational transconductance amplifiers, and resistors. The main features of the circuit are the following: it uses only resistors without recourse to any external capacitors. Therefore, it is attractive for monolithic implementation. It can be used with any mini/microcomputer or microprocessor-based system. It is possible to obtain a linear relationship between the control voltage and the frequency of oscillation. Experimental results are presented