磁致伸缩液位传感器中高分辨力时间量检测

高分辨力时间量检测是磁致伸缩液位传感器实现高准确度测量的关键技术之一.针对磁致伸缩液位传感器的国产化开发研制中的时间量检测问题,提出采用复杂可编程逻辑器件(CPLD)实现高分辨力时间量检测的方案.通过理论分析和实践证明:该方案可以满足磁致伸缩液位传感器对时间量检测的功能要求.该方案所用器件少、电路简单,可供有关国产化开发研制的技术人员参考.     

基于电容传感器的毛细管粘度计液位自动检测方法

针对现有毛细管粘度计液位手动计时检测方法的不足,设计了一种电容式液位传感器,提出了基于电容式液位传感器的毛细管粘度仪自动液位检测方法.通过实时跟踪电容量的变化,采用基于极大值判别的一阶差分阈值法自动判定计时起点和计时终点,实现毛细管粘度计的液位自动检测和自动读数,研制了智能粘度仪.结合实验结果,分析了电容式液位测量的误差因素并给出了去误差方法.智能粘度仪的实际应用表明,这种液位检测方法测量准确,抗干扰能力强,适用于重力式毛细管粘度计的液位自动检测.     

磁致伸缩液位传感器检测信号影响因素分析及实验研究

磁致伸缩液位传感器作为液位测量装置,其检测信号对磁致伸缩液位传感器性能产生直接的影响,因此检测信号影响因素分析对优化传感器的性能至关重要。本文从检测线圈结构和脉冲电流参数对检测信号的影响进行讨论,建立了基于检测线圈的等效电路模型,使得在确立线圈结构参数时有了理论依据;观察检测信号波形变化趋势,得到感应信号随影响因素的变化曲线,从而得出液位传感器最优参数。优化后的液位传感器,提高了检测信号的抗干扰能力及其稳定性。该研究结果为磁致伸缩液位传感器的优化设计提供理论基础与指导。     

一种基于传感器的小区水管道监测系统

正本发明公开了一种基于传感器的小区水管道监测系统,包括设置于水管道上端的无线液位传感器和控制平台,无线液位传感器与控制平台相连,将检测到的液位信息发送到控制平台;控制平台包括微处理器以及分别与微处理器相连的显示屏、报警装置。本发明利用无线液位传感器对下水管道的液位进行检测,可以将无线液位传感器设置到下水管道的任何位置,检测的范围变得很大;无线液位传感器与控制平台之间通过无线传输,传输的距离远,一个控制平台可以监控多个无线传感器,可以对多条管道进行监控。     

基于Laguerre基函数的液位传感器温度补偿方法

针对环境温度影响液位传感器的检测问题,提出了基于Laguerre基函数的液位非线性校正和温度补偿的复合校正模型,采用递推最小二乘(RLS)法对标定液位进行拟合以确定复合补偿模型的参数.根据液位传感器的测量值和环境温度可高精度计算出实际液位.仿真结果表明:补偿后的最大相对误差不超过(3.4145×10-7)％,具有良好的非线性校正和温度补偿效果,在液位检测领域具有重要的理论和应用价值.     

一种基于超声阻抗和回波能量的液位检测方法

针对超声波液位检测方法中,传感器和容器壁间的耦合度不佳所带来的稳定性和可靠性降低的问题,提出了一种基于阻抗法并利用回波能量来实现液位检测的方法.该方法利用液位上下方气液介质的阻抗不相等的特性,计算和比较两个接收传感器所接收到的回波能量之间的差异,以此来确定液位的位置.实验结果表明,该方法能够有效地克服因耦合条件不佳所带来的问题,检测精度满足应用需求.     

一种电容阵列式液位传感器的设计与实现

通过对电容式液位传感器的分析与研究,设计了一种新型电容阵列式液位传感器.介绍了电容阵列式液位传感器的原理和设计方案.将电容-极板设计成阵列式结构,另一极板共用,采用基于充放电原理的电容检测电路,用单片机STC89C52控制传感器中电容器的选通、数据的采集和处理,并计算出液位值,输出转换成4～20mA电流信号.实测结果表明:该液位传感器精度可达0.3%FS,零点输出稳定,漂移小,受温度影响小,热零点漂移指标优于2×10-5FS/℃.     

基于ADμC812的专用超声波液位传感器

针对易燃、易爆化学物质储罐内液位及相关量难检测的问题 ,基于ADμC812芯片设计了一套用于远距离、大量程、非接触检测的超声波液位传感器。该传感器具有自增益、可编程和扩展性能好等优点 ,可以检测所有沸点高于储存温度的介质液位 ,对其它同类传感器的远距离检测及智能化实现有良好的参考价值。     

光纤传感器在液位检测中的应用

针对目前科学研究和工业生产中常遇到的液位检测问题,介绍一种基于光学全反射和折射原理的光纤传感器,重点论述了传感器探头形状、光源的选择对传感器性能的影响,对传感器的光学传输特性进行了分析.与传统的液位传感器相比,该传感器不受电磁干扰的影响,耐高温,耐高压,抗腐蚀,可在有毒、核辐射等恶劣环境下正常工作.     

一种基于光纤光栅压力传感阵列的飞机燃油液位测量方法研究

本文提出了一种基于光纤光栅压力传感器阵列的飞机燃油液位传感系统,研究了基于聚氨酯材料的压力敏感薄膜和光纤光栅压力传感器的制造工艺,通过光纤光栅(FBG)压力传感器阵列搭建了燃油液位传感系统,开展了液位传感实验。实验结果表明,该系统在75cm液位量程范围内可实现16.09pm/cm的测量灵敏度,最大相对误差<４％。论文提出的基于线性拟合曲线截距测量的液位高度计算方法,可以克服实际应用中测量液体密度和重力加速度变化对液位测量精度的影响,保证了系统的检测精度。该光纤光栅液位传感器为飞机燃油液位检测提供了一种新的技术思路。     

Prospects for the application of liquid‐crystal cells for the registration and visualization of mechanical oscillations in biomedical technologies

Abstract— The background involving the use of liquid‐crystal cells (LCC) in biomedical technologies will be discussed. The possible types of sensors of mechanical vibrations can be constructed on the basis of a highly sensitive liquid‐crystal cell with an initial homeotropic orientation. They are especially effective in the registration of low‐frequency processes such as human breathing. The possible methods of improving the technical characteristics of liquid‐crystal sensors due to the application of an electric field or by using specially designed LCCs will be discussed. Such cells can also be applied to the visualization of breathing.     

Method for flow measurement in microfluidic channels based on electrical impedance spectroscopy

We have developed and characterized two novel micro flow sensors based on measuring the electrical impedance of the interface between the flowing liquid and metallic electrodes embedded on the channel walls. These flow sensors are very simple to fabricate and use, are extremely compact and can easily be integrated into most microfluidic systems. One of these devices is a micropore with two tantalum/platinum electrodes on its edges; the other is a micro channel with two tantalum/platinum electrodes placed perpendicular to the channel on its walls. In both sensors the flow rate is measured via the electrical impedance between the two metallic electrodes, which is the impedance of two metal–liquid junctions in series. The dependency of the metal–liquid junction impedance on the flow rate of the liquid has been studied. The effects of different parameters on the sensor’s outputs and its noise behavior are investigated. Design guidelines are extracted and applied to achieve highly sensitive micro flow sensors with low noise.     

The cleanroom-free rapid fabrication of a liquid conductivity sensor for surface water quality monitoring

Conductivity is an important issue of water quality detection. Although there are a number of microfluidic liquid conductivity sensors, most of them were difficult to fabricate and required cleanroom facilities, which significantly increased the cost of sensors. Here, we presented a novel liquid conductivity sensor that was built on interdigitated copper electrodes. Microscale sensor electrodes can be fabricated through the modified microfabrication process without any help of cleanroom facilities. In comparison with FEA simulation and commercial conductivity device, measured results showed that the fabricated liquid conductivity sensor was able to measure a wide range of liquids. Considering the ease of fabrication and its low cost, the cleanroom-free fabricated sensors have much potential for water quality monitoring.     

Tank monitoring: a pAMN case study

The introduction of probabilistic behaviour into the B-method is a recent development. In addition to allowing probabilistic behaviour to be modelled, the relationship between expected values of the machine state can be expressed and verified. This paper explores the application of probabilistic B to a simple case study: tracking the volume of liquid held in a tank by measuring the flow of liquid into it. The flow can change as time progresses, and sensors are used to measure the flow with some degree of accuracy and reliability, modelled as non-deterministic and probabilistic behaviour respectively. At the specification level, the analysis is concerned with the expectation clause in the probabilistic B machine and its consistency with machine operations. At the refinement level, refinement and equivalence laws on probabilistic GSL are used to establish that a particular design of sensors delivers the required level of reliability.     

Tank Monitoring: A pAMN Case Study

The introduction of probabilistic behaviour into the B-Method is a recent development. In addition to allowing probabilistic behaviour to be modelled, the relationship between expected values of the machine state can be expressed and verified. This paper explores the application of probabilistic B to a simple case study: tracking the volume of liquid held in a tank by measuring the flow of liquid into it. The flow can change as time progresses, and sensors are used to measure the flow with some degree of accuracy and reliability, modelled as non-deterministic and probabilistic behaviour respectively. At the specification level, the analysis is concerned with the expectation clause in the probabilistic B machine and its consistency with machine operations. At the refinement level, refinement and equivalence laws on probabilistic GSL are used to establish that a particular design of sensors delivers the required level of reliability.     

基于光电传感器的液位检测方法与装置

针对液位检测中液面气泡的干扰问题,提出一种基于双光电传感器和动态阈值的液位检测方法与装置。分析了该液位检测方法的基本原理,阐述了该光电液位检测装置的结构和测试过程。经过实验与数据分析,结果表明：该光电液位检测方法简单实用,具有较高的精度,在待测液体液面有大量气泡情况下检测精度仍可达0．2mm,特别适用于液面易产生气泡液体的液位检测。     

智能化铁路罐车液位测量系统的设计

设计了一种智能化铁路罐车液位测量系统。系统采用电容式差压传感器来获得罐车内液体的高度,采用热敏电阻器作为温度探测元件对系统进行温度补偿。传感器的输出通过C/U转换电路及A/D转换后输入单片机进行数据处理显示罐车内液位的高度。实验表明:测量系统的分辨力达到1 mm;测量误差不大于±5mm。该系统对于液位的测量具有较高的精度,可以实现铁路罐车液位测量的自动化。     

Diagnostic techniques for the dynamics of a thin liquid film under forced flow and evaporating conditions

Motivated by quantification of micro-hydrodynamics of a thin liquid film which is present in industrial processes, such as spray cooling, heating (e.g., boiling with the macrolayer and the microlayer), coating, cleaning, and lubrication, we use micro-conductive probes and confocal optical sensors to measure the thickness and dynamic characteristics of a liquid film on a silicon wafer surface with or without heating. The simultaneous measurement on the same liquid film shows that the two techniques are in a good agreement with respect to accuracy, but the optical sensors have a much higher acquisition rate up to 30 kHz which is more suitable for rapid process. The optical sensors are therefore used to measure the instantaneous film thickness in an isothermal flow over a silicon wafer, obtaining the film thickness profile and the interfacial wave. The dynamic thickness of an evaporating film on a horizontal silicon wafer surface is also recorded by the optical sensor for the first time. The results indicate that the critical thickness initiating film instability on the silicon wafer is around 84 μm at heat flux of ~56 kW/m². In general, the tests performed show that the confocal optical sensor is capable of measuring liquid film dynamics at various conditions, while the micro-conductive probe can be used to calibrate the optical sensor by simultaneous measurement of a film under quasi-steady state. The micro-experimental methods provide the solid platform for further investigation of the liquid film dynamics affected by physicochemical properties of the liquid and surfaces as well as thermal-hydraulic conditions.     

Lateral field excited Y-cut langasite bulk acoustic wave sensor

Previous studies have shown that lateral field excited (LFE) devices on AT-cut quartz are sensitive to liquid electrical property changes. AT-cut quartz LFE devices have low piezoelectric coupling factors. To further improve electrical sensitivities of LFE sensors, it is necessary to study LFE sensors based on other piezoelectric materials with higher coupling factors. In this paper, LFE sensors on Y-cut langasite, which has twice the higher piezoelectric coupling factor of AT-cut quartz, are investigated. Several Y-cut langasite LFE sensors are designed, fabricated, and tested. The experimental results show that the devices are over 6 times more sensitive to liquid conductivity changes and about 2.5 times more sensitive to liquid permittivity changes compared to AT-cut quartz LFE devices. It was also found that the Y-cut langasite LFE devices are about 1.3 times more sensitive to changes in liquid acoustic viscosity compared to the AT-cut quartz LFE devices.     

石英上准纵漏表面声波在液体传感方面的潜在应用

本文报道了石英材料上一种新的可用于液体传感的准纵漏声表面波模式的传播方向 ,即 Euler角为 [0°,136°,5 0°]的传播方向 ,并对该传播方向上准纵漏声表面波在液体传感方面的应用进行了初步研究 .结果表明 :与目前常用液体声表面波传感器所用声波模式所在传播方向相比较 ,这种新的传播方向上存在较少的声表面波模式 ,当应用于液体传感时只有准纵漏声表面波一种模式存在 .特别是 ,该传播方向上准纵漏声表面波频率温度系数实验测量值为 - 31.13ppm/℃ .这些特性使得本文所提传播方向上准纵漏声表面波具有很好的应用前景 .