传感器通信电子工程类外文翻译@中英文翻译@外文文献翻译

What is a smart sensor One of the biggest advances in automation has been the development and spread of smart sensors. But what exactly is a smart sensor? Experts from six sensor manufacturers define this term. A good working smart sensor definition comes from Tom Griffiths, product manager, Honeywell Industrial Measurement and Control. Smart sensors, he says, are sensors and instrument packages that are microprocessor driven and include features such as communication capability and on-board diagnostics that provide information to a monitoring system and/or operator to increase operational efficiency and reduce maintenance costs. No failure to communicate The benefit of the smart sensor, says Bill Black, controllers product manager at GE Fanuc Automation, is the wealth of information that can be gathered from the process to reduce downtime and improve quality. David Edeal, Temposonics product manager, MTS Sensors, expands on that: The basic premise of distributed intelligence, he says, is that complete knowledge of a system, subsystem, or components state at the right place and time enables the ability to make optimal process control decisions. Adds John Keating, product marketing manager for the Checker machine vision unit at Cognex, For a (machine vision) sensor to really be smart, it should not require the user to understand machine vision. A smart sensor must communicate. At the most basic level, an intelligent sensor has the ability to communicate information beyond the basic feedback signals that are derived from its application. says Edeal. This can be a HART signal superimposed on a standard 4-20 mA process output, a bus system, or wireless arrangement. A growing factor in this area is IEEE 1451, a family of smart transducer interface standards intended to give plug-and-play functionality to sensors from different makers. Diagnose, program Smart sensors can self-monitor for any aspect of their operation, including photo eye dirty, out of tolerance, or failed switch, says GE Fanucs Black. Add to this, says Helge Hornis, intelligent systems manager, Pepperl+Fuchs, coil monitoring functions, target out of range, or target too close. It may also compensate for changes in operating conditions. A smart sensor, says Dan Armentrout, strategic creative director, Omron Electronics LLC, must monitor itself and its surroundings and then make a decision to compensate for the changes automatically or alert someone for needed attention. Many smart sensors can be re-ranged in the field, offering settable parameters that allow users to substitute several standard sensors, says Hornis. For example, typically sensors are ordered to be normally open (NO) or normally closed (NC). An intelligent sensor can be configured to be either one of these kinds. Intelligent sensors have numerous advantages. As the cost of embedded computing power continues to decrease, smart devices will be used in more applications. Internal diagnostics alone can recover the investment quickly by helping avoid costly downtime. Sensors: Getting into Position As the saying goes, No matter where you go, there you are. Still, most applications require a bit more precision and repeatability than that, so heres advice on how to select and locate position sensors. The article contains online extra material. Whats the right position sensor for a particular application? It depends on required precision, repeatability, speed, budget, connectivity, conditions, and location, among other factors. You can bet that taking the right measurement is the first step to closing the loop on any successful application. Sensor technologies that can detect position are nearly as diverse as applications in providing feedback for machine control and other uses. Spatial possibilities are linear, area, rotational, and three-dimensional. In some applications, theyre used in combination. Sensing elements are equally diverse. Ken Brey, technical director, DMC Inc., a Chicago-based system integrator, outlined some the following position-sensing options. Think digitally For digital position feedback: Incremental encoders are supported by all motion controllers； come in rotary and linear varieties and in many resolutions； are simulated by many other devices； and require a homing process to reference the machine to a physical marker, and when power is turned off. Absolute encoders are natively supported by fewer motion controllers； can be used by all controllers that have sufficient available digital inputs； report a complete position within their range (typically one revolution)； and do not require homing. Resolvers are more immune to high-level noise in welding applications； come standard on some larger motors； simulate incremental encoders when used with appropriate servo amps； and can simulate absolute encoders with some servo amps. Dual-encoder feedback, generally under-used, is natively supported by most motion controllers； uses one encoder attached to the motor and another attached directly to the load； and is beneficial when the mechanical connection between motor and load is flexible or can slip. Vision systems , used widely for inspection, can also be used for position feedback. Such systems locate objects in multiple dimensions, typically X, Y, and rotation； frequently find parts on a conveyor； and are increasing in speed and simplicity. A metal rolling, stamping, and cut-off application provides an example of dual-encoder feedback use, Brey says. It required rapid and accurate indexing of material through a roll mill for a stamping process. The roll mill creates an inconsistent amount of material stretch and roller slip, Brey explains. By using the encoder on the outgoing material as position feedback and the motor resolver as velocity feedback in a dual-loop configuration, the system was tuned stable and a single index move provided an accurate index length. It was much faster and more accurate than making a primary move, measuring the error, then having to make a second correction move, he says. Creative, economical Sam Hammond, chief engineer, Innoventor, a St. Louis, MO-area system integrator, suggests that the applications purpose should guide selection of position sensors； measurements and feedback dont have to be complex. Creative implementations can provide simple, economical solutions, he says. For instance, for sequencing, proximity sensors serve well in many instances. Recent sensor applications include the AGV mentioned in lead image and the following. In a machine to apply the top seals to tea containers, proximity and through-beam sensors locate incoming packages. National Instruments vision system images are processed to find location of a bar code on a pre-applied label, and then give appropriate motor commands to achieve the desired position (rotation) setting to apply one of 125 label types. Two types of position sensors were used. One was a simple inductive proximity sensor, used to monitor machine status to ensure various motion components were in the right position for motion to occur. The camera also served as a position sensor, chosen because of its multi purpose use, feature location, and ability to read bar codes. A progressive-die stamping machine operates in closed loop. A linear output proximity sensor provides control feedback for optimizing die operation； a servo motor adjusts die position in the bend stage. A linear proximity sensor was selected to give a dimensional readout from the metal stamping operation； data are used in a closed-loop control system. Part inspection uses a laser distance measurement device to determine surface flatness. Sensor measures deviation in return beams, indicating different surface attributes to 10 microns in size. An encoder wouldnt have worked because distance was more than a meter. Laser measurement was the technology chosen because it had very high spatial resolution, did not require surface contact, and had a very high distance resolution. An automotive key and lock assembly system uses a proximity sensor for detecting a cap in the ready position. A laser profile sensor applied with a robot measures the key profile. What to use, where? Sensor manufacturers agree that matching advantages inherent to certain position sensing technologies can help various applications. David Edeal, product marketing manager, MTS Sensors Div., says, for harsh factory automation environments, the most significant factors even above speed and accuracy in customers minds are product durability and reliability. Therefore, products with inherently non-contact sensing technologies (inductive, magnetostrictive, laser, etc.) have a significant advantage over those that rely on physical contact (resistive, cable extension, etc.) Other important factors, Edeal says, are product range of use and application flexibility. In other words, technologies that can accommodate significant variations in stroke range, environmental conditions, and can provide a wide range of interface options are of great value to customers who would prefer to avoid sourcing a large variety of sensor types. All technologies are inherently limited with respect to these requirements, which is why there are so many options. Edeal suggest that higher cost of fitting some technologies to a certain application creates a limitation, such as with linear variable differential transformers. For example, LVDTs with stroke lengths longer than 12 inches are rare because of the larger product envelope (about twice the stroke length) and higher material and manufacturing costs. On the other hand, magnetostrictive sensing technology has always required conditioning electronics. With the advent of microelectronics and the use of ASICs, we have progressed to a point where, today, a wide range of programmable output types (such as analog, encoder, and fieldbus) are available in the same compact package. Key for sensor manufacturers is to push the envelope to extend the range of use (advantages) while minimizing the limitations (disadvantages) of their technologies. Listen to your app Different sensor types offer distinct advantages for various uses, agrees Tom Corbett, product manager, Pepperl+Fuchs. Sometimes the application itself is the deciding factor on which mode of sensing is required. For example, a machine surface or conveyor belt within the sensing area could mean the difference between using a standard diffused mode sensor, and using a diffused mode sensor with background suppression. While standard diffused mode models are not able to ignore such background objects, background suppression models evaluate light differently to differentiate between the target surface and background surfaces. Similarly, Corbett continues, a shiny target in a retro-reflective application may require use of a polarized retro-reflective model sensor. Whereas a standard retro-reflective sensor could falsely trigger when presented with a shiny target, a polarized retro-reflective model uses a polarizing filter to distinguish the shiny target from the reflector. MTS Edeal says, Each technology has ideal applications, which tend to magnify its advantages and minimize its disadvantages. For example, in the wood products industry, where high precision； varied stroke ranges； and immunity to high shock and vibration, electromagnetic interference, and temperature fluxuations are critical, magnetostrictive position sensors are the primary linear feedback option. Likewise, rotary optical encoders are an ideal fit for motor feedback because of their packaging, response speed, accuracy, durability, and noise immunity. When applied correctly, linear position sensors can help designers to ensure optimum machine productivity over the long haul. Thinking broadly first, then more narrowly, is often the best way to design sensors into a system. Edeal says, Sensor specifications should be developed by starting from the machine/system-level requirements and working back toward the subsystem, and finally component level. This is typically done, but what often happens is that some system-level specifications are not properly or completely translated back to component requirements (not that this is a trivial undertaking). For example, how machine operation might create unique or additional environmental challenges (temperature, vibration, etc.) may not be clear without in-depth analysis or past experience. This can result in an under-specified sensor in the worst situation or alternatively an over-specified product where conservative estimates are applied. Open or closed Early in design, those involved need to decide if the architecture will be open-loop or closed-loop. Paul Ruland, product manager, AutomationDirect, says, Cost and performance are generally the two main criteria used to decide between open-loop or closed-loop control in electromechanical positioning systems. Open-loop controls, such as stepping systems, can often be extremely reliable and accurate when properly sized for the system. The burden of tuning a closed-loop system prior to operation is not required here, which inherently makes it easy to apply. Both types can usually be controlled by the same motion controller. A NEMA 23 stepping motor with micro-stepping drive is now available for as little as $188, compared to an equivalent servo system at about $700. Edeal suggests, Control systems are created to automate processes and there are many good examples of high-performance control systems that require little if any feedback. However, where structural system (plant) or input (demand or disturbance) changes occur, feedback is necessary to manage unanticipated changes. On the process side, accuracy both static and dynamic is important for end product quality, and system stability and repeatability (robustness) are important for machine productivity. For example, Edeal says, in a machining or injection molding application, the tool, mold or ram position feedback is critical to the final dimension of the fabricated part. With rare exceptions, dimensional accuracy of the part will never surpass that of the position sensor. Similarly, bandwidth (response speed) of the sensor may, along with response limitations of the actuators, limit production rates. Finally, a sensor that is only accurate over a narrow range of operating conditions will not be sufficient in these types of environments where high shock and vibration and dramatic temperature variations are common. The latest What are the latest position sensing technologies to apply to manufacturing and machining processes and why? Ruland says, Some of the latest developments in positioning technologies for manufacturing applications can be found in even the simplest of devices, such as new lower-cost proximity switches. Many of these prox devices are now available for as little as $20 and in much smaller form factors, down to 3 mm diameter. Some specialty models are also available with increased response frequencies up to 20 kHz. Where mounting difficulties and cost of an encoder are sometimes impractical, proximity switches provide an attractive alternative； many position control applications can benefit from increased performance, smaller package size, and lower purchase price and installation cost. Corbett concurs. Photoelectric sensors are getting smaller, more durable, and flexible, and are packed with more standard features than ever before. Some new photoelectrics are about half the size of conventional cylindrical housings and feature welded housings compared with standard glued housings. Such features are very desirable in manufacturing and machining applications where space is critical and durability is a must. And more flexible connectivity and mounting options side mount or snout mount are available from the same product allow users to adapt a standard sensor to their machine, rather than vice versa. Another simple innovation, Corbett says, is use of highly visible, 360-degree LED that clearly display status information from any point of view. Such enhanced LED indicates overload and marginal excess gain, in addition to power and output. Such sensors offer adjustable sensitivity as standard, but are available with optional tamperproof housings to prevent unauthorized adjustments. Photoelectric Sensors Photoelectric sensors are typically available in at least nine or more sensing modes, use two light sources, are encapsulated in three categories of package sizes, offer five or more sensing ranges, and can be purchased in various combinations of mounting styles, outputs, and operating voltages. It creates a bewildering array of sensor possibilities and a catalog full of options. This plethora of choices can be narrowed in two ways: The first has to do with the object being sensed. Second involves the sensors environment. Boxed in The first question to ask is: What is the sensor supposed to detect? Are we doing bottles? Or are we detecting cardboard boxes? says Greg Knutson, a senior applications engineer with sensor manufacturer Banner Engineering. Optical properties and physical distances will determine which sensing mode and what light source work best. In the case of uniformly colored boxes, for example, it might be possible to use an inexpensive diffuse sensor, which reflects light from the box. The same solution, however, cant be used when the boxes are multicolored and thus differ in reflectivity. In that case, the best solution might be an opposed or retroreflective mode sensor. Here, the system works by blocking a beam. When a box is in position, the beam is interrupted and the box detected. Without transparent boxes, the technique should yield reliable results. Several sensors could gauge boxes of different heights. Distance plays a role in selecting the light source, which can either be an LED or a laser. LED is less expensive. However, because LED are a more diffuse light source, they are better suited for shorter distances. A laser can be focused on a spot, yielding a beam that can reach long distances. Tight focus can also be important when small features have to be sensed. If a small feature has to be spotted from several feet, it may be necessary to use a laser. Laser sensors used to cost many times more than LED. That differential has dropped with the plummeting price of laser diodes. Theres still a premium for using a laser, but its not as large as in the past. Environmental challenges Operating environment is the other primary determining factor in choosing a sensor. Some industries, such food and automotive, tend to be messy, dangerous, or both. In the case of food processing, humidity can be high and a lot of fluids can be present. Automotive manufacturing sites that process engines and other components may include grit, lubricants, and coolants. In such situations, the sensors environmental rating is of concern. If the sensor cant handle dirt, then it cant be used. Such considerations also impact the sensing range needed because it may be necessary to station the sensor out of harms way and at a greater distance than would otherwise be desirable. Active alarming and notification may be useful if lens gets dirty and signal degrades. Similar environmental issues apply to the sensors size, which can range from smaller than a finger to something larger than an open hand. A smaller sensor can be more expensive than a larger one because it costs more to pack everything into a small space. Smaller sensors also have a smaller area to collect light and therefore tend to have less range and reduced optical performance. Those drawbacks have to be balanced against a smaller size being a better fit for the amount of physical space available. Sensors used in semiconductor clean room equipment, for example, dont face harsh environmental conditions, but do have to operate in tight spaces. Sensing distances typically run a few inches, thus the sensors tend to be small. They also often make use of fiber optics to bring light into and out of the area where changes are being detected. Mounting, pricing Another factor to consider is the mounting system. Frequently, sensors must be mechanically protected with shrouds and other means. Such mechanical and optical protection can cost more than the sensor itself a consideration for the buying process. If vendors have flexible mounting systems and a protective mounting arrangement for sensors, the products could be easier to implement and last longer. List prices for standard photoelectric sensors range from $50 or so to about $100. Laser and specialty photoelectric sensors cost between $150 and $500. Features such as a low-grade housing, standard optical performance, and limited or no external adjustments characterize the lower ends of each category. The higher end will have a high-grade housing, such as stainless steel or aluminum, high optical performance, and be adjustable in terms of gain or allow timing and other options. Low-end products are suitable for general applications, while those at the higher end may offer application-specific operation at high speed, high temperature, or in explosive environments. Finally, keep in mind that one sensing technology may not meet all of the needs of an application. And if needs change, a completely different sensor technology may be required. Having to switch to a new approach can be made simpler if a vendor offers multiple technologies in the same housing and mounting footprint, notes Ed Myers, product manager at sensor manufacturer Pepperl+Fuchs. If thats the case, then one technology can be more easily swapped out for another as needs change. 译文 什么是智能传感器 自动化领域所取得的一项最大进展就是智能传感器的发展与广泛使用。但究竟什么是“智能”传感器？下面，自 6 个传感器厂家的专家对这一术语进行了定义。 据 Honeywell 工业测量与控制部产品经理 Tom Griffiths 的定义：“一个良好的智能传感器是由微处理器驱动的传感器与仪表套装，并且具有通信与板载诊断等功能，为监控系统和 /或操作员提供相关信息，以提高工作效率及减少维护成本。” 无 故障通信 “智能传感器的优势，” GE Fanuc 自动化公司控制器产品经理 Bill Black说，“是能从过程中收集大量的信息以减少宕机时间及提高质量。” MTS 传感器公司 Temposonics（磁致伸缩位移传感器）产品经理 David Edeal 对此补充说：“分布式智能的基本前提是，在适当位置和时间拥有有关系统、子系统或组件的状态的全部知识，以进行最优的过程控制决策。” Cognex 公司 Checker 机器视觉部产品营销经理 John Keating 继续补充说，“对于一种真正的智能（机器视觉）传感器 ，它应该不需要使用者懂得机器视觉。” 智能传感器必须具备通信功能。“最起码，除了满足最基本应用的反馈信号，智能传感器必须能传输其它信息。” Edeal 表示。这可以是叠加在标准 4-20 mA 过程输出、总线系统或无线安排上的 HART（可寻址远程传感器高速通道的开放通信协议）信号。该领域正在增长的因素是 IEEE 1451 一系列旨在为不同厂家生产的传感器提供即插即用能力的智能传感器接口标准。 诊断与程序 智能传感器可对其运行的各个方面进行自监控，包括“摄像头的污浊，超容忍限或不能开关等，” GE Fanuc 自动化公司的 Black 说。 Pepperl+Fuchs 公司智能系统经理 Helge Hornis 补充说，“（除此之外），还有线圈监控功能，目标超出范围或太近。”它也可以对工况的变化进行补偿。“智能传感器，” Omron 电子有限公司战略创意总监 Dan Armentrout 表示，“必须首先能监视自身及周围的环境，然后再决定是否对变化进行自动补偿或对相关人员发出警告。” 很多智能传感器都能重装到控制现场，通过提供“可设置参数，使用户能替换一些标准传感器，” Hornis 说道，“例如，典型的传感器一般都设 置为常开（ NO）或常关（ NC），而智能传感器则能设置为以上任何一种状态。” 智能传感器拥有很多优势。随着嵌入式计算功能的成本继续减少，“智能”器件将被更多地应用。独立的内部诊断功能可避免代价高昂的宕机，从而迅速收回投资。 传感器 ：越来越到位 正如人们所说的：“无论你到哪里，他都与你同在。”因为大多数的应用仍然都要求这所表达的更高精度和更好的可重复性，所以这里介绍关于如何选择和安装位置传感器的建议。 什么样的传感器才是对特定应用的传感器呢？这取决于对精度、可重复性、速度、预算、连接性、环境和位置的要求， 以及其他一些因素。你说的没错，选用正确的测量方法是任何成功应用中闭合回路的第一步。 可检测位置的传感器技术几乎与为机器控制和其他用途提供反馈的应用一样多种多样。空间可能是直线的、平面的、旋转的和三维的。在一些应用中，它们结合使用。传感元件同样也是多种多样。 DMC 公司（总部位于芝加哥的系统集成商）的技术总监 Ken Brey 勾画了选择位置传感器的几点选择。 数字化思考 对数字式位置回馈： 增量型编码器 所有的运动控制器都支持；有旋转和直线类型以及多种解决方案；被多种其他设备仿真；当断电时，要求具 有回复原位过程，以实现为机器提供物理标记参考。 绝对编码器 天生就只有很少的运动控制器支持；可以用于具有足够多可用数字输入的控制器；在它们的范围内（通常是一个旋转）可以报告完整的位置；不要求回复原位。 解算器 在焊接应用中对高等级噪声有很高的免疫力；在一些较大的电机中成为使用标准；当配合恰当的伺服放大器使用时可模拟增量型编码器；和一些伺服放大器共同使用可以模拟绝对编码器。 双编码器反馈 通常未被充 分利用，天生地可被大部分的运动控制器支持；一个编码器安放在电机上，另一个直接安放在负载上；当电机和负载间的机械连接是柔性的或者是能滑动的时候，是非常有益处的。 视觉系统 广泛地用于检测，也可用于位置反馈。这样的系统可在多维空间定位目标，典型的是 X、 Y 和旋转；通常用于查找传送带上的元件，目前正在提高速度和简单易用性。 一个金属轧制、冲压和切割应用提供了双编码反馈使用实例。“它要求通过轧机为冲压过程快速和精确地标定材料指数。轧机产生数量不一致的材料伸展和辊子滑移” Brey 解释说。 “通过在双回 路配置中，在输出的材料上使用编码器作为位置反馈和电机解算器作为速度反馈，系统被调节得稳定，且单一标定移动提供精确的标定长度。这比先移动、后测量误差，再不得不进行第二次校正移动要快得多，且更精确。”他说。 有创造性，经济节约 Innoventor 公司 (密苏里州圣路易斯市的系统集成商 ) 的总工程师 Sam Hammond 建议说：应用目的决定位置传感器的选择；测量与反馈不应该很复杂。“创造性的实施可提供简单、经济的解决方案，”他说。例如，对排序问题，接近开关在许多场合可发挥很好的作用。 近来传感器的应用包 括在前面图片中提到的 AGV（自动引导车）以及下面一些。 在一个用于密封茶叶容器顶盖的机器中，接近开关和对射式传感器定位靠近的包装。 NI 公司的视觉系统获得图像并被处理，来发现提前印在标签上的条形码的位置，然后给出恰当的电机指令以实现理想的位置（旋转）放置来应用 125种标签类型中的一种。其中用到了两种类型的位置传感器。一种是简单的感应式接近开关，用于监测机器状态以确保即将发生运动的各种运动元件处于正确的位置。照相机也作为位置传感器使用，选择它是因为它的多目的用途、特征定位和读条码能力。 连续冲模（ progressive-die）冲床闭环运行。线性输出接近开关为优化冲模运行提供控制反馈；伺服电机在弯曲阶段调整冲模位置。选用线性接近开关从金属冲压运行状态给出尺寸读数；数据用于闭环控制系统。 元件检查使用激光距离测量设备来确定表面光滑度。传感器测量返回光束的偏移，由 10 微米的尺寸即可指示出不同的表面。编码器在距离大于 1 米的时候不能工作。选择激光测量技术是因为它具有非常高的空间分辨率，不要求表面接触，以及具有相当高的距离分辨率。 汽车钥匙和门锁集成系统使用接近开关监测在就位位置的顶盖。与自动机械装置一起应 用的激光外形传感器测量钥匙外形。 使用什么？在哪里使用？ 传感器供应商认为发挥各种位置传感技术的内在优势能有利于各种应用。 MTS 公司传感器部的产品市场经理 David Edeal 说：“对苛刻的工厂自动化环境来说，在顾客眼中最重要的因素，是产品的耐用性和可靠性，这甚至超过速度和精度。因此，具有内在非接触式传感技术（电磁感应、磁致伸缩、激光等）的产品比那些依靠物理接触的技术（电阻式、电缆扩展等）具有非常巨大的优势。” 其他重要的因素是产品使用范围和应用灵活性。 Edeal 说：“换句话说，能够适应行程 范围、环境条件的重大变化和能够提供大范围接口选择的技术对更喜欢避免使用多种传感器类型的客户具有重大价值。关于这些要求，所有技术天生都有缺陷，这就是为什么会有这么多种选择。” Edeal 暗示使某些技术适合特定应用的高额成本带来了一种限制，例如对线形可变差动变压器（ LVDT）的限制。“行程长度超过 12 英尺的线性可变差动变压器少见，因为较大的产品外壳（约是行程长度的两倍）和很高的原料和制造成本。另一方面，磁致伸缩传感技术总是要求调节电子设备。随着微电子学的出现和专用集成电路的应用，今天我们已经前进到了这样一点，在 相同的紧凑封装中有多种可编程输出类型（如模拟、编码器和现场总线）可用。传感器供应商的关键是推动封装的发展，以扩展使用范围（优点），同时最小化他们技术上的局限。” 听听你的应用 不同的传感器类型对不同的用途提供特有的优点， Pepperl+Fuchs 公司的产品经理 Tom Corbett 同意这一点。“有时应用本身是需要哪一种传感模式的决定因素。例如，在感应区域内的机器表面或传送带将意味着使用标准扩散模式传感器与使用带背景抑制的扩散模式传感器会有不同。虽然标准扩散模式不能够忽略这样的背景目标，但是背景抑制 模型能稍有不同地评估区别目标表面和背景表面。” Corbett 继续说，“相似的，在反射应用中，一个发亮的对象会要求使用偏振反射式的传感器。尽管标准反射式传感器在对准一个闪亮目标时会误触发，但偏振反射式采用偏振滤光片来区分发光物体和反射体。” MTS 公司的 Edeal 说：“每一种技术都有理想的应用，此时它容易放大它的优点并最小化它的缺点。例如，在木材制品行业中高精度，可变行程范围，抵抗高冲击与振动、电磁干扰和温度起伏的能力是非常重要的；磁致伸缩位置传感器是线性反馈的首选。同样，旋转光编码器是电机反馈的理想 适用品，因为他们具有的封装、响应速度、精度、耐用性和对噪声的抵抗力。如果应用正确，线性位置传感器能帮助设计者在很长一段时间内确保最佳的机器生产率。” 先从大范围考虑，再缩小考虑范围，这常常是为系统设计传感器的最佳方法。Edeal 说：“传感器的规范应该从机器 /系统级的要求开始制订，然后向后朝子系统级细化，最终到达元件级。这是典型的做法，但是经常发生的是一些系统级的规范没有恰当地或完整地向后细化翻译为元件要求（这并非是一件微不足道的工作）。例如，在没有深入分析或不具备以往经验的情况下，机器如何运行会产生独特 的或额外的环境挑战（温度、振动等）可能是不清楚的。这会导致在最坏的情况下过低的指定了传感器，或者另外一种情况是应用于保守估计的情况下，过高地指定了产品。” 开环还是闭环 在设计的初期，那些涉及需要决定结构体系的因素是开环还是闭环。AutomationDirect 公司