Simple Steps to Selecting the Right AccelerometerWord文档下载推荐.docx

1、 Faced with choices of technology, shape, size, and sensing range, novices as well as more experienced users can be intimidated when examining an accelerometer manufacturers catalog or Web site. The path described in this article will help you find your way through the thicket of options to choose t

2、he optimum accelerometer for your application. 在寻找加速表？查找加速表厂商的样本或者网站，会发现选择是如此之多，包括技术、结构、规格和感测范围，所以无论是新手还是经验丰富的用户都会头痛不已。Technology Selection技术选择The first step in the selection process is to determine the type of measurement to be made. There are three popular technologies used for acceleration measur

3、ements. 选择流程的第一步就是确定测量的类型。加速度测量有3种常用的技术。Piezoelectric （PE） accelerometers are the most widely used accelerometers for test and measurement applications. These devices offer a very wide measurement frequency range （a few Hz to 30 kHz） and are available in a range of sensitivities, weights, sizes, and

4、 shapes. PE accelerometers are available with a charge or voltage （IEPE） output, discussed later in this article. They are appropriate for both shock and vibration measurements. 压电式（PE）加速表是测试和测量应用场合中应用最广泛的加速表。其测量频率范围非常宽（从几Hz到30kHz），而且有多种敏感度、重量、规格和结构可供选择。压电式加速表都带有电荷或电压（IEPE）输出，本文稍后会有这方面的介绍。这个类型的加速表可用

5、于冲击测量和振动测量。Piezoresistive （PR） accelerometers generally have low sensitivity making them desirable for shock measurements and less useful for vibration measurements. They are also used extensively in transportation crash tests. PR accelerometers generally have a wide bandwidth （from a few hundred Hz

6、 to130 kHz） and the frequency response goes down to 0 Hz （often called DC responding） or steady state, so they can measure long-duration transients. 压阻式（PR）加速表的敏感度较低，适合用于冲击测试，但振动测试较少会用。其广泛用于交通碰撞测试。压阻式加速表通常带宽较宽（几百Hz到130kHz以上），频率响应可低至0Hz（通常称之为直流响应）或稳态，所以可用于测量长周期内的瞬时变量。Variable capacitance （VC） is amon

7、g the newer accelerometer technologies. Like piezoresistive accelerometers, VC accelerometers are DC responding. They have high sensitivities, a narrow bandwidth （from 15 Hz to 3000 Hz）, and outstanding temperature stability. Thermal zero and sensitivity shifts can be as low as 1.5% over a temperatu

8、re range of 180C. These devices are suited for measuring low-frequency vibration, motion, and steady-state acceleration. 电容可变式（VC）加速表是比较新的加速表技术之一。跟压阻式加速表类似，电容可变式加速表是直流响应。敏感度高，带宽窄（15Hz到3000Hz），但是温度稳定性初中。180C温度范围内，热力学零度和敏感度变化可以保持在1.5%的水平。适合用于测量低频振动、动作和稳态加速度。Type of Measurement测量方式First, well describe

9、the basic measurement types, providing more detail later on. For the purposes of this article, we will divide acceleration measurements into the following categories: 首先，我们要描述出基本的测量类型，稍后提供更多细节。就本文的目的而言，我们可以将加速度测量分成以下几大类：VibrationAn object is said to vibrate when it executes an oscillatory motion abo

10、ut a position of equilibrium. Vibration is found in the transportation, aerospace, and industrial environments as well as when simulated by a shaker system. 振动一个物体在平衡位置产生振荡，就可以说这个物体在振动。振动现象常见于交通运输、航天航空和各类工业环境，当然也可以用一个振荡器系统来模拟这个现象。ShockA sudden transient excitation of a structure that generally excit

11、es the structures resonances. A shock pulse can be produced from an explosion, a hammer striking an object, or a vehicle crash. 冲击一个结构的瞬时激发，主要激发结构的谐振。爆炸，锤击物体或车辆碰撞都可产生冲击脉冲。MotionMotion is a slow-moving event lasting from 1 s to several minutes, such as the movement of a robotic arm or an automotive s

12、uspension. 运动运动是移动缓慢的事件，持续时间从1秒到几分钟，例如机械臂或者汽车悬挂的移动。SeismicThis is more like a slow-motion or a low-frequency vibration. This measurement usually requires a specialized ,low-noise, high-resolution accelerometer. Seismic accelerometers are used to measure the motion of bridges, floors, and earthquakes

13、. 地震更像是低速运动或者低频振动。这种类型的测量通常需要专业的低噪音高分辨率的加速表。地震加速表用于测量桥梁、楼层和地震的运动。General Considerations主要考虑因素Before we discuss the technologies and applications in greater detail, here are a few general considerations. 我们进一步讨论技术和应用场合之前，先说一下主要考虑的因素。Frequency response is the accelerometers electrical output vs. a mec

14、hanical excitation over a frequency range with a fixed amplitude and it is an important parameter when considering any accelerometer. The frequency range will usually be determined by the test specifications or by the user. It is usually specified within 5% of the reference frequency （usually 100 Hz

15、）. Many devices will have the specifications extended Figure 1. A miniature triaxial accelerometer incorporates three accelerometers in a single package to simultaneously measure acceleration in three orthogonal axes 图1 一个小型化的三轴向加速表，在一个壳体内集成了3个加速表，同步测量相互垂直的3个轴向的加速度。to 1 dB and in some cases 3dB. The

16、 preceding limits express the accuracy that can be expected over a given frequency range. Most data sheets will have a typical frequency response curve to assist the user. The curves illustrate how the accelerometers accuracy varies over a specified frequency range. 频率响应是指加速表的电气输出与一稳幅频率范围内机械激发的对比。这是

17、考虑加速表时的一个重要的参数。频率范围通常由测试规格或用户来确定。通常指定为参考频率（通常为100Hz）的5%。许多产品已经将这个范围扩大到了1 dB，更有甚者到了3dB。先前的限制值就是在一个指定范围的期望精确度。多数的参数资料页都会有典型的频率响应曲线，给用户提供方便。曲线显示了加速表在一个指定频率范围内的精确度变化。Another consideration is the number of axes to be measured. Accelerometers are available in single-axis and triaxial （3-axis） versions （Fi

18、gure 1）. An alternative approach to making a three-axis measurement is to mount three accelerometers on a triaxial mounting block. Both methods allow for the measurement of three orthogonal axes simultaneously. 另外需要考虑的就是需要测量的轴向数量。加速表有单轴向和3轴向（图1）。可用安装在3轴向安装模块上的3个减速表来作为3轴向测量的代替方案。两种方法都可以允许同步测量3个互相垂直的轴

19、向。Vibration振动Piezoelectric accelerometers are the first choice for most vibration measurements since they have a wide frequency response, good sensitivity and resolution, and are easy to install. There are two types of piezoelectric accelerometers: the basic charge-mode accelerometer and the voltage

20、-mode Internal Electronic Piezoelectric （IEPE） accelerometer. 压电式加速表是多数振动测量的首选，因为其响应频率宽，敏感度和分辨率良好，并易于安装。压电式加速表主要有两种：基本电荷模式加速表和电压模式内部电子压电式（IEPE）加速表。In recent years, the IEPE type has become the most commonly used accelerometer type because of its ease of use. IEPE sensors are often sold under differe

21、nt trademarked names, but most comply with a pseudo industry standard and are interchangeable between brand names. （Authors note: Be sure that the power source current and voltage are compatible with the accelerometer youve selected to achieve optimal performance and to avoid possible damage.） Basic

22、ally, an IEPE accelerometer has a charge amplifier built into the accelerometer. As a result, the sensor requires no external charge amplifier and uses ordinary, low-cost cable. The accelerometer does require a constant current power source and many DA systems have built-in power sources. For a know

23、n vibration range and an operating temperature that lies within the range of 55CC to 125C consider using an IEPE device. Note that high-temperature versions of some models have a maximum operating temperature of 175C. 最近几年，内部电子压电式因其易用性，就成了最常用的加速表。内部电子压电式传感器有很多牌子，但多数遵循一个事实行业标准，各个牌子可互换。（作者提示：请确保电源电流和电

24、压与所选的加速表兼容，以实现最优的性能，避免可能的损坏。）基本上，内部电子压电式加速表具有一个内置的电荷放大器，使用了常规且成本低廉的电缆。加速表确实需要稳定的电流电源，许多DA系统具有内置的电源。对于一个一直的振动范围，且范围在55CC 到 125C的工作温度，可以考虑使用内部电子压电式加速表。注意，一些耐高温型号最高工作温度可到175C。The advantages of charge-mode piezoelectric accelerometers include high-temperature operation and an extremely wide amplitude ra

25、nge, which is largely determined by the charge amplifier setting. An IEPE accelerometer has a fixed amplitude range. A typical charge-mode accelerometer will have an operating temperature range of 55C to 288C. Special-purpose accelerometers are available for extreme environments as low as 269C to as

26、 high as 760C. Special radiation-hardened charge-mode accelerometers are available for use in a nuclear environment. 电荷模式压电式加速表的优势包括耐高温，非常宽的幅度范围，大都由电荷放大器的设置决定。内部电子压电式加速表具有固定的幅度范围。电荷模式的工作温度范围在55C 和 288C之间。一些专用加速表可用于一些极端环境，温度最低可到269C，最高可到760辐射加硬的电荷模式加速表可用于核环境。Unlike the IEPE accelerometer, the charge-

27、mode accelerometer requires the use of a special low-noise cable, which is expensive when compared to the standard commercial coaxial cable. A charge amplifier or an in-line charge converter is also required for operation. Charge-mode accelerometers are preferred for high-temperature operation （abov

28、e 175C） or in cases where the maximum acceleration is unknown. 跟内部电子压电式加速表不同，电荷模式加速表需要使用专用的低噪音电缆，与标准的商用同轴电缆相比价格比较贵。工作时，还需要电荷放大器或一个同轴电荷转换器。电荷模式加速表更多用于高温工作环境（175C以上）或用于最高加速还位置的场合。Figure 2. Variable capacitance accelerometer shown with a popular mounting configuration. 图2 图中电容可变式减速表带常用的安装配置In instances

29、 where vibration measurements at very low frequencies are required, consider choosing a VC accelerometer （Figure 2）. VC accelerometers have a frequency response from 0 Hz to 1 kHz, depending on the sensitivity required. When making very low frequency measurements, a VC accelerometer with a frequency

30、 range from 015 Hz will provide a sensitivity of 1 V/g. VC accelerometers are useful on electrohydraulic shakers, to make flutter measurements, and for many transportation applications, such as testing automotive and suspension systems and making railroad ride and sway measurements. 在一些需要超低频振动测量的场合，

31、可考虑选用电容可变式减速表（图2）。电容可表示加速表的频率响应在0 Hz 和 1 kHz之间，取决于所需的敏感度。超低频测量时，频率范围在0-15Hz的电容可变式加速表可提供1 V/g的敏感度。电容可变式减速表可用于电液振荡器，作摆动测量，还可用于多种交通运输应用场合，例如测试汽车和悬挂系统，作铁轨乘波和摇摆测量。Shock冲击Two technologies are available for shock measurements and, depending on the shock levels and the final data required, you can choose from a variety of accelerometers. It is important to know the expected shock lev