带有电极挂料的电容式物位传感器的数学模型分析

传统电容式物位传感器存在着严重的缺陷，即存在电极挂料电容对测量的影响，中分析了物位传感器电极挂料的等效电路，提出了它的数学模型，计算了它的等效复数阻抗，得到电极挂料复阻抗的实部与虚部相等的结论，利用这一结论可以扣除电极挂料电容，从而消除它的影响，提高测量准确度。     

射频导纳原理在料位测量中的应用

固态、液态（包括浆体）料位测量技术广泛应用于石油、化工、能源、食品、矿山、储运等工业生产领域，95％以上的容量测量也是通过料位测量得到的。传统料位测量方法多种多样，如电容式、放射线式、机电式、声波式等，其中又以电容式（又称做射频式）应用最为广泛。它耐腐蚀、抗高温、抗高压，但有一个致命的缺陷，即测量黏附性导电物料时，物料会黏附在传感电极的外套绝缘罩上（挂料），形成虚假物位，产生很大的测量误差，使仪表无法工作。正是这一点妨碍了电容式物位仪表的更广泛推广应用。应用射频导纳技术，对传统的电容式物位仪表进行…     

系列物位测量仪表开创物位新纪元

系列物位测量仪表开创物位新纪元ＣＷ－１００１型智能物位计（国家专利产品）该物位计采用计算机控制，具有精密的机械传动机构，精心设计的各种物位触头及任意长度的钢带。保证您在各种复杂的环境下自如地进行物位测量。·精密的传感器及计算机控制，实现了触头整个运动...     

一种简单的定位式超声波物位计

文章介绍的物位计是根据介质声阻抗的不同来确定物位的,即当超声波换能器发射面前的介质变更即声阻抗变化时,反射到发射电路的阻抗也将发生变化,进而引起发射电路电压的变化,由此变化即可指示物位。     

不盲目地推陈出新——问卷调查：用户更倾向于使用操作简单的物位计

化工生产流程中一般都会用到物位计，无论是限位性还是连续性的物位测量。在选择物位计时，用户更倾向于选择简单的集成和易于操作使用的产品，较少选择市场上比较新的产品。     

高粉尘浓度下的准确物位测量

粉质PVC原料料仓的物位测量对各种料位检测设备都提出了很高的要求。近一年半以来,某生产厂料仓中的导波雷达物位计可靠地完成了这一高难度的料位检测任务。     

全能的重锤式物位计

为了检测料仓中粘结剂颗粒的物位，就需要使用能够不受粘着性物料影响的物位检测技术。UWT公司研发生产的机电一体化重锤式物位计能够很好地完成这一检测任务，能够克服料仓中物料的粘附。     

BM100物位计在火电厂中的应用

煤粉仓、煤灰仓的物位测量问题 ,长期以来一直得不到有效解决。这不仅因为传统的物位测量原理有各种局限性 ,还因为煤粉仓及煤灰仓中煤（灰）粉的介电常数较小 ,加上仓内环境的恶劣 ,常规的电测方式均不能胜任。在电厂自动化监控水平已显著提高的今天 ,这一监控“盲点”迫切需要得到认真解决。经过多方考察及现场试验证明 ,采用ＢＭ１００物位测量装置能有效地解决煤粉（灰）仓的物位测量问题。１ 基本原理ＢＭ１００物位计是以时域反射（Ｔ Ｄ ＲＴｉｍｅＤｏｍａｉｎＲｅ ｆｉｅｃｔｏｍｅｔｒｙ）原理为基础设计的 ,Ｔ Ｄ Ｒ原理原用于通…     

解决松散物料物位测量难题——阻旋式物位计适用手特殊的应用场合

在松散物料的生产和物流过程中，自动化程度已经越来越高。但在这些过程中，很多应用场合都对物位计提出了很高的要求，例如极高的测量精度、严格的环保和卫生法规。只有高性能的物位计才能够满足这些测量任务的要求。     

MEMS电容薄膜真空计微电容测量研究进展

MEMS电容薄膜真空计的小型化和整体性能与微电容测量电路密切相关。由于不同领域的应用需求,MEMS电容薄膜真空规管具有不同的敏感电容结构,而相应的微电容测量法也不同。单侧电极微电容测量法电路结构简单,易于实现;双侧电极微电容测量法电路结构较复杂,但该电路可以减小寄生电容及温度的影响而获得高分辨率;静电力平衡式结构下微电容测量法用闭环电路,在高精度测量的同时还能拓宽真空计的动态范围。介绍了测量原理、电路结构及性能,可以看出,具有精度高、功耗低、易集成的特点,能够应用于多种不同类型的MEMS电容式传感器的微小电容测量电路,对今后MEMS应用从航空航天等高精尖领域向人工智能物联网领域的拓展具有重要意义。     

电容传感器新型电容测量电路设计

提出了一种基于V／T变换的用于电容传感器的电容测量电路。它将被测微小电容变化量转换成时间信号并由单片机进行处理，电路结构简单，电路中没有影响测量稳定性和产生零点漂移的元器件，大幅度地降低了测量过程中的噪声。     

电容/电压转换电路CAV424及其在油品含水率测量的应用

提出了一种电容传感器调理电路的新方法,引入了用于电容/电压信号转换的集成电路CAV424,以及CAV424在油品含水率测量中的应用。     

新型多孔介质局部含湿量测试仪的研究

采用针型电容测湿传感器和单片微处理机技术研制成一种新型多孔介质局部含湿量测试仪。本文论述该测试仪的组成、工作原理和硬、软件结构及其特点。实验结果表明，可望满足多孔介质局部含湿量测量的实用要求。     

Capacitance-type blade-tip clearance measurement system using adual amplifier with ramp/DC inputs and integration

The analysis and prototype results for a dual-amplifier circuit for measuring blade-tip clearance in turbine engines are presented. The capacitance between the blade tip and mounted capacitance electrode within a guard ring of a probe forms one of the feedback elements of an operational amplifier (op amp). The differential equation governing the circuit taking into consideration the nonideal features of the op amp was formulated and solved for two types of inputs (ramp and DC) that are of interest for the application. Under certain time-dependent constraints, it is shown that (1) with a ramp input the circuit has an output voltage proportional to the static tip clearance capacitance, and (2) with a DC input, the output is proportional to the derivative of the clearance capacitance. and subsequent integration recovers the dynamic capacitance. The technique accommodates long cable lengths and environmentally induced changes in cable and probe parameters. System implementation for both static and dynamic measurements having the same high sensitivity is also presented     

Microelectronic capacitance transducer for particle detection

This paper describes the CMOS circuit design of a sensor for detecting changes of capacitance due, for instance, to the incidence of particles or bubbles on the electrodes. The circuit is based on a simple design originating at the University of California, Berkeley, for measuring crosstalk on integrated circuits. The basic front-end sensor circuit comprises eight MOSFETs and has a sensitivity of 40 mV/fF. A differential amplifier receives the outputs from two sensor circuits each having 20-/spl mu/m square inter-digitated electrodes. The resulting sensitivity of the fabricated sensor is 1 V/fF with a noise level equivalent to 10 aF. Monte Carlo circuit simulations have been used to identify transistor dimensions to yield acceptable yield, and prototype custom silicon chips have been fabricated using a 0.8-/spl mu/m CMOS process. Static and dynamic tests, using polyamide particles as small as 10-/spl mu/m diameter, verify correct operation of the sensors. The sensor is now being developed for application in miniature electrical tomography systems.     

微小电容测量仪500fF/1MHz溯源方法研究

fF量级高频微小电容测量在军工电子产品领域有着重要作用,针对微小电容测量仪500fF/1MHz点无法溯源的现状,研制了惰性气体封装的500fF高频标准电容器作为传递标准。建立高频小电容测量模型,基于“反算法”估算出500fF高频标准电容器分布参数,称作“理论推导”溯源方案,不确定度优于0.15%;利用3台同等量级的高频微小电容测量传递标准,称作“计量比对”溯源方案,不确定度优于0.07%。利用以上2种方案对同1台仪器开展溯源,实验数据结果基本一致,能够满足用户使用要求,为更低容值、更高频率的微小电容的溯源提供了可参考的路径。     

Analysis of Power-Supply Interference Effects on Direct Sensor-to-Microcontroller Interfaces

This paper analyzes the effects of power-supply interference on direct sensor-to-microcontroller interfaces based on measuring the charging/discharging time of an RC circuit that includes the sensor. Power-supply interference becomes a source of trigger noise that affects the measurement of the charging/discharging time and, hence, the measurement of the sensor resistance or capacitance. The measurement uncertainty increases proportionally to the amplitude of the interference and depends on its frequency. Such interference effects are smaller when measuring the discharging time and can be further reduced by placing an additional resistor in the interface circuit. Experimental data obtained from a PIC microcontroller agree with the theoretical predictions     

Mobile patient monitoring based on impedance-loaded SAW-sensors

A remotely requestable, passive, short-range sensor network for measuring small voltages is presented. The sensor system is able to simultaneously monitor six small voltages in millivolt-range, and it can be used for Holter-electrocardiogram (ECG) and other biopotential monitoring, or in industrial applications. The sensors are based on a surface acoustic wave (SAW) delay line with voltage-dependent, impedance loading on a reflector interdigital transducer (IDT). The load circuit impedance is varied by the capacitance of the voltage-controlled varactor. High resolution is achieved by developing a MOS-capacitor with a thin oxide, low flat-band voltage, and zero-voltage capacitance in the space-charge region, as well as a high-Q-microcoil by thick metal electroplating. Simultaneous monitoring of multiple potentials is realized by time-division-multiplexing of different sensor signals.     

A simple interface circuit to measure very small capacitancechanges in capacitive sensors

This paper presents an easy-to-design interface circuit to measure very small-percentage capacitance variations in capacitive sensors, especially suitable for industrial measurements. A computer-controlled 24-bit A/D converter is employed to obtain a higher resolution. This interface circuit can be used with various types of capacitive sensors. The most interesting thing is, that the measurement results through this interface circuit are independent of the initial capacitance of the sensor. In addition, the double differential operating principle used here minimizes the error caused by coupling and stray capacitance of sensor probes. The operating principle of the designed interface circuit, the major assumptions made, test data, and possible future developments are discussed