Piezoelectric based resonant mass sensor using phase measurement

The paper presents design, development and testing of a resonant sensor to measure mass in the range of 0-12 g. The sensor is built using cantilever structure with piezoelectric excitation, sensing and microcontroller based closed loop electronics. The sensor measures the unknown mass by measuring the shift in resonance frequency of the cantilever beam. The shift in resonance frequency for a change in mass is detected by measuring the phase difference between the piezoelectric sensor output and actuator input using microcontroller. The proposed measurement system is simple and accuracy is found to be ±1.2% of full scale deflection.     

Erosion thermocouple temperature acquisition system

Aiming at high requirements of temperature measurement system in high temperature,high pressure,highly corrosive and other special environments,a temperature acquisition system based on field-programmable gate array(FPGA) which is the controller of the system is designed.Also a Flash memory is used as the memory and an erosion thermocouple is used as sensor of the system.Compared with the traditional system using complex programmable logic device(CPLD)and microcontroller unit(MCU)as the main body,this system has some advantages,such as short response time,small volume,no loss of data once power is off,high precision,stability and reliability.And the sensor of the system can be reused.In this paper,boiling water experiment is used to verify accuracy of the system.The millisecond level signal from firecrackers is for verifying the stability and fast response characteristics of the system.The results of experiment indicate that the temperature measurement system is more suitable for the field of explosion and other environments which have high requirements for the system.     

Design of C8051F350-based Intelligent Pressure Sensor

In order to overcome the deficiencies of traditional pressure sensors,a kind of intelligent pressure sensors with temperature correction is designed.According to the intelligent sensor system of composition and range of applications,with fully taking into account the parameters of the connection between components of co-ordination,we chose a good usability,high reliability and low cost components composed of the entire measurement system,with controlling and dealing with in 80C51 microcontroller,the system had the temperature and pressure parameters with automatic measurement,amplification,A/D conversion,the weak signal locked amplification,as well as Phase-Sensitive Detection(PSD),common-mode signal rejection,the collected signal de-noising processing,cross-sensitivity of the decoupling and show the results.It also has a self-test,automatic temperature compensation and on-site communications and other functions.     

Networking Intelligent Pressure Sensor Using Digital Lock-in Amplification Technology

Introducing a System-on-Chip(SoC)microcontroller(C8051F350)into a ceramic pressure sensor has resulted in the design of a networking intelligent sensor.An improved algorithm for digital phase-sensitive detection is used to perform lock-in amplification of the sensor signal.The compensation for the sensor error is realized by the detection of the sensor’s supply voltage and working temperature.The system also has the function of short/open circuit fault detection and can communicate with other digital equipment through an RS-485 communication interface.In the design,full utilization of the SoC microcontroller’s internal resource results in the simple hardware structure.Experimental results show that the error of the sensor is less than 0.5% at range ratio 1∶10.Employing the microcontroller and using lock-in amplification algorithm are an effective method for achieving an intelligent sensor of slowly-varying physical quantities,thereby improving the measuring accuracy and performance.     

基于Lonworks总线的分布式测温系统的设计

本文基于LonWorks现场总线技术,采用新型单总线数字温度传感器DS18B20提出了一种新型的分布式测温系统。系统由一台上位机和多个智能节点组成,智能节点采用单片机MSP430F149为主处理器,神经元芯片3150为从处理器。用单片机进行温度数据采集,输出数据经收发器通过LON网络传给上位机,实现了对温度的实时、准确及自动检测。     

Auto-calibration and -compensation of a capacitive pressure sensor using multilayer perceptrons

Using multilayer perceptrons (MLPs), a smart model for a capacitive pressure sensor (CPS) is proposed. When the ambient temperature changes, the nonlinear response characteristics of a CPS may vary widely. Under such conditions, calibration of the sensor and compensation of the nonlinear sensor characteristics to obtain correct readout becomes a difficult task. The proposed MLP model can provide automatic nonlinear compensation and calibration of the CPS characteristics. A microcontroller unit (MCU)-based implementation scheme for this model is also considered. Simulation results show that this model can estimate the pressure with a maximum full-scale error of +/- 1% over a variation of temperature from -50 to 150 degrees C.     

Modeling and development of an ANN-based smart pressure sensor in a dynamic environment

In many engineering applications, a capacitive pressure sensor (CPS) is placed in a dynamic environment in which the temperature variation is quite large. Since the response characteristics of a CPS are highly nonlinear and temperature dependent, in such situations, complex signal processing techniques are needed to obtain correct readout of the applied pressure. We have proposed an artificial neural network (ANN)-based smart capacitive pressure sensor, whose response characteristics can be estimated within an accuracy of ±1% error over a wide variation of temperature starting from −50°C to 150°C. This modeling scheme automatically takes care of all the nonidealities, such as, nonlinearity, offset, gain and temperature dependence, of the sensor. A novel idea of automatic collection of temperature information and its feeding into the ANN model is also proposed. In the practical implementation of this scheme, the hardware complexity poses a serious impairment. Since the tanh() functions are needed for implementation in the ANN-based model, to reduce the hardware requirement, we provide a simple scheme for computation of tanh(). Sensitivity analysis of the model with respect to the finite word-length constraint on the final stored weight values, and number of terms used in the implementation of tanh() function, have been carried out. A microcontroller-based implementation scheme for the ANN-based model is also suggested.     

A diaphragm-type fiber Bragg grating pressure sensor with temperature compensation

A diaphragm-type fiber Bragg grating (FBG) pressure sensor with two bare FBGs directly bonded on a circular diaphragm along the radial direction has been proposed and studied. Measurement principle and simulation analysis of the pressure sensor are introduced. Using the wavelength shift difference of the two FBGs which respectively measure the positive and negative strain as sensing signal, the pressure sensitivity is increased and the temperature cross-sensitivity is compensated. Experimental results indicate that the measurement sensitivity is 1.57 pm/kPa in a range from 0 to 1 MPa, the correlative coefficient reaches 99.996%, and the temperature compensation performance is distinct. This kind of pressure sensor could be used to measure and monitor the static/dynamic pressure of gas or liquid.     

智能型温湿度传感器的研究

】采用ＰＩＣ１６Ｃ５４单片机实现热温度和湿度传感器,采用软件校准技术补偿电压、时间、温度漂移以及元器件标称误差,并具有ＲＳ４８５通讯功能。     

LonWorks现场总线在分布式测温系统中的应用

以LonWorks现场总线技术为基础，以新型单总线数字温度传感器DS18820为测温元件，提出了一套新型的分布式测温系统。整个测温系统由一台上位机和多个Host—Based结构的智能节点组成，其中智能节点采用单片机AT89C51为主处理器、神经元芯片TMPN3120为从处理器、FTT-10A为收发器。系统中单片机将采集来的温度数据传送给神经元芯片，然后数据经由收发器通过LON网络传输到上位机。该系统具有结构简单、测量精度高、抗干扰能力强等特点，具有广泛的应用前景。     

An orifice meter for bidirectional air flow measurements: Influence of gas thermo-hygrometric content on static response and bidirectionality

This paper presents the design and calibration of an ISO non-compliant orifice plate flowmeter whose intended use is for respiratory function measurements in the bidirectional air flow range ±9 L/min.The novelty of the proposed sensor consists of a plate beveled in both upstream and downstream sides: a symmetrical geometry is adopted in order to perform bidirectional measurements of flow rate. A mathematical model is introduced to quantify the influence of temperature on the sensor output. Four different positions of the pressure static taps are evaluated in order to maximize bidirectionality. An index is also introduced in order to quantitatively estimate the anti-symmetry of the sensor's response curve.Trials are carried out to evaluate the influence on sensor output of air temperatures (22 °C, 30 °C and 37 °C) at different values of relative humidity (5%, 55% and 85%). Experimental data show a quite good agreement with the theoretical model (R²>0.98 in each condition).The influence of air temperature on the sensor output is minimized by introducing a correction factor based on the theoretical model leading to measurement repeatability better than 2% in overall range of calibration. The mean sensitivity in the calibration range is about 2 kPa L⁻¹·min allowing to obtain a sensor discrimination threshold lower than 0.2 L/min in both directions. The time constant of the whole measurement system, equal to 2.40±0.03 ms, leads to a bandwidth up to 80 Hz making the sensor suitable for respiratory function measurements.     

MEMS压差传感器在小型无人机空速测量中的应用

介绍了一种基于MEMS压差传感器和数字信号处理器(DSP)的小型无人机空速测量系统的实现方法.根据实际需求对压差传感器进行了温度补偿,并采用最小二乘法消除器件和电路的非线性;经实验测试,空速在13～50 m/s范围内,该系统的测量精度在±3％以内.该空速测量系统具有体积小、重量轻、功耗低、工作可靠等优点.     

高精度快响应海洋测温系统设计

针对海洋投弃式仪器的快速响应高精度测温要求,提出了一种新型的温度传感器设计方案.对高灵敏度负温度系数热敏电阻进行特殊封装完成传感器制作,利用MSP430单片机和24位AD7799实现了系统的数字化,通过多点校准插值的方法校准非线性传感器使系统获得测温高精度.经过实验室和南海的大量实验证明该系统工作稳定,可靠性高.实验数据表明系统的响应时间低于100 ms,分辨率超过0.001℃,测温精度可达0.02℃.     

轮胎红外测温监测防爆系统设计

基于红外测温技术的轮胎温度检测装置的基本原理和结构特点,实时监测轮胎表面温度分布情况,设计出一套通用的轮胎动态温度检测装置.将四个红外探头安装在轮毂上,将红外探头检测到的温度模拟信号输入模数转换器,转换成数字信号,再将数字信号输入单片机,设计单片机程序,通过单片机处理比较四个数字信号,并判断胎压是否过高,通过液晶显示屏...     

可穿戴式电子织物仿生皮肤设计与应用研究

为满足电子仿生皮肤的穿戴舒适度,提出了一种电容式柔性织物压力传感器,采用丝网印刷工艺,以织物为柔性基体,炭黑填充型复合弹性电介质和有机硅导电银胶制备柔性压敏触觉单元。介绍了压敏单元的结构设计与感知机理,研究了炭黑含量与温度对织物触觉单元性能的影响,改善了该电子织物的输出线性度与重复性,实现了0~700 k Pa量程范围迟滞误差为5.6%,动态响应时间为89 ms,灵敏度为0.025 36%/KPa,同时,引入温度补偿以提升触觉感知准确性。通过将织物压敏单元应用于足底压力信息的时空分布研究和机械手的软抓取实验,其足底压力分布及触觉感知实验结果表明,该电容式柔性织物压力传感器具有良好的工作稳定性与触觉感知功能,为可穿戴式人工皮肤的研究提供了一种设计方案。     

Development of a Digital Conductivity Meter with Frequency Response for Remote Monitoring

Abstract

A simple and inexpensive conductivity meter with frequency response is shown. Good linearity is achieved up to 10 mS but, by using a special function, given from a theoretical standpoint, precision measurements can be done up to 100 mS. To allow temperature compensation, another similar circuit is used, where the conductivity cell is replaced by a negative temperature coefficient resistor (NTC). The intrinsic non-linearity of this component was not enough to limit its use as a temperature sensor within a several-degrees range. The good signal-to-noise ratio obtained for long distances, the integrative response in pulsecounter mode, and the independence between frequency and supply voltage make this equipment specially suitable for field monitoring.     

双斜波法测量微小电容电路的研究与设计

微小电容的测量技术成为电容传感器技术被广泛应用的关键,针对目前小电容测量电路存在的问题,提出一种基于测量三角波斜度的小电容检测方法,采用PIC单片机为主的测量电路,电容检测分辨率可达0.005pF。此小电容测量系统具有高精度和稳定度、测量范围广、测量时间短的特点,适合于实时可视化测量。     

A relative calibration method for a valve leakage rate measurement system

This paper presents a relative calibration method for an internal valve leakage rate measurement system using both microcontroller and acoustic emission (AE) methods. An air jet was selected to calibrate because it provides a frequency spectrum similar to the AE spectrum obtained from the valve leak, especially in the frequency range of 100-300 kHz. Three AE sensors mounted on a valve were used to validate the system calibration. Ratios between the average energy (AErms) were obtained from each pair of sensors, and these ratios were used to transfer the leakage AErms value. Subsequence, its performance to predict the leakage rate in the laboratory and in the field was tested. The error is less than 5% in almost cases. Its benefit is to reduce the recalibration time when a part of measurement system is changed. Accordingly, inexpensive equipment including an AE sensor was built, and its system performance was revealed.     

膜片式微型F-P腔光纤压力传感器研究

对基于Fabry-Perot（F-P）干涉仪原理的膜片式微型光纤压力传感器的制作工艺进行了实验研究。在单模光纤端面上直接熔接外径约175μm的毛细石英管,在石英管的另一端制作敏感膜片,从而在光纤端面与膜片内表面之间形成F-P干涉腔。首先采用电弧熔接、切割、腐蚀膜片的方法制作了石英膜片式压力传感器,该传感器在0-3.1MPa压强范围内F-P腔的腔长变化灵敏度为41.09nm/MPa,压强测量分辨率681Pa,并具有很小的温度敏感系数。在30-140℃的温度范围内,温度交差敏感小于1.07KPa/℃。为了克服石英膜片减薄困难的缺点,选用聚合物材料（PSQ）作为压力敏感膜片制作了F-P传感器,室温下在0.1-2.1MPa压强范围内PSQ膜片的F-P腔长变化灵敏度达到 1 886.85nm/MPa,压强测量分辨率达到53Pa。     

高精度随钻定向测量仪的设计

以3轴加速度传感器和3轴磁通门传感器为基础,设计了定向传感器的角度测量模型;通过对传感器温度误差和安装误差的分析,研究了影响传感器精度的因素,提出了能有效提高传感器测量精度的误差校正模型.以微控制器MSP430F149和模数转换器ADS1216为核心,设计了硬件滤波电路和信号采样电路;基于角度测量模型和误差校正模型,给出了姿态参数采集的主程序和误差补偿程序流程图.实验分析表明:在高温高压强振的环境下该系统达到了所提出的精度指标.