电子信息工程外文资料翻译---压电式加速度传感器及其应用.doc

1、The piezoelectric acceleration sensor and its applicationAbstract: in recent years the piezoelectric acceleration sensor got bigger development, this article expounds the piezoelectric acceleration sensor principle and constitute element, and the analysis of its frequency characteristics and sensiti

2、vity, exploring the error formation factors, summarizes its application in the field of engineering control. One, the piezoelectric acceleration sensor principle The piezoelectric acceleration sensor and says piezoelectric accelerometer. It also belongs to the inertial sensor. It is the use of certa

3、in substances, such as quartz crystals piezoelectric effect, in the accelerometer, quality by vibration of piezoelectric element and in the force changed also. When measured vibration frequency is far lower than the natural frequency of the accelerometer, the change of force by using is proportional

4、 to the acceleration. Because of the piezoelectric sensor output signal is weak charge, and sensor itself has a great internal resistance, so little, the output energy behind the circuit to bring certain difficulties. Therefore, usually the sensor signal to lose to high input impedance of the preamp

5、lifier. After impedance transformation can be used in the future, amplification, detection circuit will signal loss to indicating meter or recorder. Second, the piezoelectric acceleration sensor constitute elements (a) center installation compression type (b) ring shear (c) triangle shearCommonly us

6、ed the piezoelectric accelerometer structure form shown in figure 13.18. S is spring, M is the mass, B is base, P is piezoelectric element, R is clamping ring. Figure 13.18 a is the central Ann loaded compressed type, piezoelectric element-quality piece of-spring system installed in the circular cen

7、ter struts, supports and base connection. This structure has high resonant frequency. However base B and the testing to like connection, if base B are the deformation will directly influence the vibration system output up. In addition, the test object and environment temperature change will affect p

8、iezoelectric element, and make preloaded force change, easy cause temperature drift. Figure 13.18 c to the triangle shear form, by clamping ring piezoelectric element will be the clip in triangle center column in prison. Accelerometer feel axial vibration, bearing the piezoelectric element by shear

9、stress. This structure deformation and temperature changes to the base have extremely good isolation effect, have higher resonance frequency and good linear. Figure 13.18 b ring, simple structure, shear can make it very small, high resonance frequency accelerometer, the ring of quality stuck to pack

10、 in the center of the ring on the pillar piezoelectric element. Due to the binder will increased with temperature become soft, so the highest working temperature is limited. Three, the piezoelectric acceleration sensor amplitude frequency characteristics The use of accelerometer ceiling depends on t

11、he amplitude frequency curve frequency resonant frequency map (figure 13.19). General small damping (z = 0.1) of the accelerometer, upper limit for the resonant frequency if the frequency of a third, can guarantee amplitude error is less than 1 dB (12%); If take for 1/5 of the resonant frequency are

12、 guaranteed amplitude error is less than 0.5 dB (6%), and phase shift less than 30. But the resonant frequency and accelerometer fixed condition, accelerometer related factory the amplitude frequency curve is given in the rigid connection get fixed. Of the actual use of the fixed method is often dif

13、ficult to reach, and rigid connection resonance frequency and use frequency will cap fell. The accelerometer and specimen of fixed method is shown in figure 13.20. Figure 13.20 a of the steel bolt, is to make the resonant frequency can achieve the best way out of the resonant frequency. Bolt may not

14、 all shake screw holes into the base, lest cause base deformation, the influence of the accelerometer outputs. In the installation of layer of the tu yi on silicon grease can increase the uneven surface of the installation of the connection reliability. Need can be used when insulation insulation bo

15、lts and mica washer to fixed accelerometer (figure 13.20 b), but the gasket should try to book. With a layer of book the wax accelerometer glued to the specimen surface smooth (figure 13.20 c), also can be used in low temperature (40 below) occasion. Handheld probe measurement vibration methods (fig

16、ure 13.20 d) on a multipoint test very convenient use, but the measurement error is bigger, repeatability, use frequency generally poor cap is not higher than 1000 Hz ac. Use special permanent magnets fixed accelerometer (figure 13.20 e), easy to use, many in the low frequency measurement in use. Th

17、is method also can make the accelerometer specimens and insulation. With rigid adhesive bolts (figure 13.20 f) or adhesive (figure 13.20 g) fixed method also long use. Some typical accelerometer with the above the resonant frequency of fixed method respectively for: steel bolts about law 31 kHz, mic

18、a gaskets 28 kHz, besmear book 29 kHz, the layer of wax with law 2 kHz, permanent magnets fixed law 7 kHz. Four, the piezoelectric acceleration sensor sensitivity The piezoelectric accelerometer, the sensitivity of piezoelectric accelerometer is power type, can see it as a sensor voltage source or c

19、harge source, the sensitivity and charge voltage sensitivity has two said method. The sensitivity The former is the accelerometer output voltage (mV) and are under the acceleration than; The latter is accelerometer output charge and are under the ratio of acceleration. Acceleration unit for m/s2, bu

20、t in vibration measurement often use standard gravity acceleration of units, 1 g g = 9.80665 m/s2. This is a kind of already accepted means, almost all vibration measurement instrument with g acceleration and in the instrument as a unit of the board face and manual drawings. For given for piezoelect

21、ric materials, with the increase of the quality of the sensitivity of the increase of piezoelectric element or increase. Generally, the greater the size of accelerometer, its inherent frequency is lower. So choose acceleration time should weigh sensitivity and structure size and the influence on the

22、 quality of additional and frequency response characteristics of the advantages and disadvantages between. Piezoelectric crystal accelerometer transverse sensitivity says it lateral (in vertical axis) accelerometer sensitive degree of transverse vibration, the sensitivity to the Lord sensitivity (th

23、at is often accelerometer voltage sensitivity or charge sensitivity) percentage said. In general on the shell marked by a red dot minimum horizontal direction, a good and the sensitivity of the accelerometer transverse sensitivity should be less than 3% of the Lord sensitivity. Therefore, the piezoe

24、lectric accelerometer test in the direction of the obvious. Five, the piezoelectric acceleration sensor error formation factors analysis Piezoelectric accelerometer preamplifier piezoelectric element stress the creation of charge after amount, this very weak charges boundary and then piezoelectric e

25、lement on the boundary conductor charged to the voltage U = q/Ca (here is the accelerometer Ca in capacitance). To determine the charge so weak (or voltage) is the key to prevent wire, the measurement circuit and accelerometer itself of charge of the leakage. In other words, piezoelectric accelerome

26、ter used the preamplifier should have extremely high input impedance, the leakage reduced to the measurement accuracy required within the limits of the piezoelectric sensors, the preamplifier: voltage amplifier and charge amplifier. The voltage amplifier is high input impedance amplifier is the prop

27、ortion of. The circuit is simple, but by connecting cables of output capacitance effects, used in general vibration measurement. A charge amplifier to be negative feedback, use of capacitance basic from the influence of the cable capacitance. In charge amplifier, usually with high quality yuan, devi

28、ces, high input impedance, but the price is more expensive. From the piezoelectric sensor mechanics model of the look, it is low pass characteristics, the original extremely low frequency vibration measurement. But in fact because of low frequency especially small amplitude vibration acceleration, t

29、he sensitivity of the sensor is small, limited, so the output signal will be weak and signal-to-noise ratio was low; Additional charge, the drift integral leakage circuit (used for measuring vibration velocity and a move), the noise of the device is inevitable, so the actual low frequency end also a

30、ppear cut-off frequency, about 0.1 1 Hz ac or so. Five, the piezoelectric acceleration sensor of practical application At present the latest IBM Thinkpad laptops in the built-in acceleration sensors, dynamic monitoring out to use notebook in the vibration, and according to the vibration data, the sy

31、stem will be intelligent choice closed or let it continue to run hard drive, so can the greatest degree of protection because, for example, the turbulence vibration work environment, or accidentally fell off the computer to do damage caused by the hard disk, the greatest degree of protection in the

32、inside of the data. Another use is the currently used digital cameras and video cameras, also have add speed sensor, used to detect when shooting in the hand of the vibration, and according to the vibration, automatic regulation to focus the camera. Generally speaking, acceleration sensor can be use

33、d in the control, the handle vibration and shaking, instruments, the brake start testing, testing, earthquake warning system, toys, structures, environmental monitoring, engineering geological exploration, vibration measurement, railway, Bridges, DAMS vibration test and analysis; The mouse, high-ris

34、e building structure dynamic characteristics and security vibration on reconnaissance. Six, the piezoelectric acceleration sensor of practical application At present the latest IBM Thinkpad laptops in the built-in acceleration sensors, dynamic monitoring out to use notebook in the vibration, and acc

35、ording to the vibration data, the system will be intelligent choice closed or let it continue to run hard drive, so can the greatest degree of protection because, for example, the turbulence vibration work environment, or accidentally fell off the computer to do damage caused by the hard disk, the g

36、reatest degree of protection in the inside of the data. Another use is the currently used digital cameras and video cameras, also have add speed sensor, used to detect when shooting in the hand of the vibration, and according to the vibration, automatic regulation to focus the camera. Generally spea

37、king, acceleration sensor can be used in the control, the handle vibration and shaking, instruments, the brake start testing, testing, earthquake warning system, toys, structures, environmental monitoring, engineering geological exploration, vibration measurement, railway, Bridges, DAMS vibration te

38、st and analysis; The mouse, high-rise building structure dynamic characteristics and security vibration on reconnaissance. 压电式加速度传感器及其应用摘要：近年来压电式加速度传感器得到了较大的发展，本文重点阐述了压电式加速度传感器的原理及其构成元件，分析了其频率特性和灵敏度，探究了其误差形成因素，概述了其在工程控制领域中的实际应用。一、 压电式加速度传感器原理压电式加速度传感器又称压电加速度计。它也属于惯性式传感器。它是利用某些物质如石英晶体的压电效应，在加速度计受振时，质

39、量块加在压电元件上的力也随之变化。当被测振动频率远低于加速度计的固有频率时，则力的变化与被测加速度成正比。由于压电式传感器的输出电信号是微弱的电荷，而且传感器本身有很大内阻，故输出能量甚微，这给后接电路带来一定困难。 为此，通常把传感器信号先输到高输入阻抗的前置放大器。经过阻抗变换以后，方可用于一般的放大、检测电路将信号输给指示 仪表或记录器。 二、压电式加速度传感器构成元件(a)中心安装压缩型 (b)环形剪切型 (c) 三角剪切型图13.18 压电式加速度计常用的压电式加速度计的结构形式如图13.18所示。S是弹簧，M是质块，B是基座，P是压电元件，R是夹持环。图13.18a是中央安 装压缩

40、型，压电元件质量块弹簧系统装在圆形中心支柱上，支柱与基座连接。这种结构有高的共振频率。然而基座B与测试对 象连接时，如果基座B有变形则将直接影响拾振器输出。此外，测试对象和环境温度变化将影响压电元件，并使预紧力发生变化， 易引起温度漂移。图13.18c为三角剪切形，压电元件由夹持环将其夹牢在三角形中心柱上。加速度计感受轴向振动时，压电元件承 受切应力。这种结构对底座变形和温度变化有极好的隔离作用，有较高的共振频率和良好的线性。图13.18b为环形剪切型，结构简单，能做成极小型、高共振频率的加速度计，环形质量块粘到装在中心支柱上的环形压电元件上。由于粘结剂会随温度增高而变软，因此最高工作温度受到

41、限制。三、压电式加速度传感器幅频特性图13.19 压电式加速度计的幅频特性曲线 加速度计的使用上限频率取决于幅频曲线中的共振频率图（图13.19）。一般小阻尼(z=0.1)的加速度计，上限频率若取为共振频率的 1/3，便可保证幅值误差低于1dB（即12%）；若取为共振频率的1/5，则可保证幅值误差小于0.5dB（即6%），相移小于30。但共振频率与加速度计的固定状况有关，加速度计出厂时给出的幅频曲线是在刚性连接的固定情况下得到的。实际使用的固定方法往往难于达到刚性连接，因而共振频率和使用上限频率都会有所下降。加速度计与试件的各种固定方法见 图13.20。图13.20 加速度计的固定方法其中图1

42、3.20a采用钢螺栓固定，是使共振频率能达到出厂共振频率的最好方法。螺栓不得全部拧入基座螺孔，以免引起基座 变形，影响加速度计的输出。在安装面上涂一层硅脂可增加不平整安装表面的连接可靠性。需要绝缘时可用绝缘螺栓和云母垫片来 固定加速度计（图13.20b），但垫圈应尽量簿。用一层簿蜡把加速度计粘在试件平整表面上（图13.20c），也可用于低温（40以下）的场合。手持探针测振方法（图13.20d）在多点测试时使用特别方便，但测量误差较大，重复性差，使用上限频率一般不高于 1000Hz。用专用永久磁铁固定加速度计（图13.20e），使用方便，多在低频测量中使用。此法也可使加速度计与试件绝缘。用硬性粘

43、接螺栓（图13.20f）或粘接剂（图13.20g）的固定方法也长使用。某种典型的加速度计采用上述各种固定方法的共振频率分别约为：钢螺栓固定法31kHz，云母垫片28kHz，涂簿蜡层29kHz，手持法2kHz，永久磁铁固定法7kHz。四、压电式加速度传感器的灵敏度压电式加速度计的灵敏度压电加速度计属发电型传感器，可把它看成电压源或电荷源，故灵敏度有电压灵敏度和 电荷灵敏度两种表示方法。前者是加速度计输出电压（mV）与所承受加速度之比；后者是加速度计输出电荷与所承受加速度之比。 加速度单位为m/s2，但在振动测量中往往用标准重力加速度g作单位，1g= 9.80665m/s2。这是一种已为大家所接受

44、的表示方式，几乎所有 测振仪器都用g作为加速度单位并在仪器的板面上和说明书中标出。对给定的压电材料而言，灵敏度随质量块的增大或压电元件的增多而增大。一般来说，加速度计尺寸越大 ，其固有频率越低。因此选用加速度计时应当权衡灵敏度和结构尺寸、附加质量的影响和频率响应特性之间的利弊。压电晶体加速度计的横向灵敏度表示它对横向（垂直于加速度计轴线）振动的敏感程度，横向灵敏度常以主灵敏度（即加速度计的电压灵敏度或电荷灵敏度）的百分比表示。一般在壳体上用小红点标出最小横向灵敏度方向，一个优良的加速度计的横向灵敏度应小于主灵敏度的3。因此，压电式加速度计在测试时具有明显的方向性。五、压电式加速度传感器误差形成

45、因素分析压电加速度计的前置放大器 压电元件受力后产生的电荷量极其微弱，这电荷使压电元件边界和接在边界上的导体充电 到电压U=q/Ca（这里Ca是加速度计的内电容）。要测定这样微弱的电荷（或电压）的关键是防止导线、测量电路和加速度计本身的电荷泄漏。换句话讲，压电加速度计所用的前置放大器应具有极高的输入阻抗，把泄漏减少到测量准确度所要求的限度以内，压电式传感器的前置放大器有：电压放大器和电荷放大器。所用电压放大器就是高输入阻抗的比例放大 器。其电路比较简单，但输出受连接电缆对地电容的影响，适用于一般振动测量。电荷放大器以电容作负反馈，使用中基本不受 电缆电容的影响。在电荷放大器中，通常用高质量的元

46、、器件，输入阻抗高，但价格也比较贵。从压电式传感器的力学模型看，它具有“低通”特性，原可测量极低频的振动。但实际上由于低频尤其小振幅振动时，加速度值小，传感器的灵敏度有限，因此输出的信号将很微弱，信噪比很低；另外电荷的泄漏，积分电路的漂移（用于测振动速度和位 移）、器件的噪声都是不可避免的，所以实际低频端也出现“截止频率”，约为0.11Hz左右。六、压电式加速度传感器的实际应用目前最新IBM Thinkpad手提电脑里就内置了加速度传感器，能够动态的监测出笔记本在使用中的振动，并根据这些振动数据，系统会智能的选择关闭硬盘还是让其继续运行，这样可以最大程度的保护由于振动，比如颠簸的工作环境，或者不小心摔了电脑做造成的硬盘损害，最大程度的保护里面的数据。另外一个用处就是目前用的数码相机和摄像机里，也有加速度传感器，用来检测拍摄时候的手部的振动，并根据这些振动，自动调节相机的聚焦。概括起来，加速度传感器可应用在控制，手柄振动和摇晃，仪器仪表，汽车制动启动检测，地震检测，报警系统，玩具，结构物、环境监视，工程测振、地质勘探、铁路、桥梁、大坝的振动测试与分析；鼠标，高层建筑结构动态特性和安全保卫振动侦察上。. .此处忽略！