傳感器通信電子工程類外文翻譯@中英文翻譯@外文文獻翻譯

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. 譯文 什么是智能傳感器 自動化領(lǐng)域所取得的一項最大進展就是智能傳感器的發(fā)展與廣泛使用。但究竟什么是“智能”傳感器？下面，自 6 個傳感器廠家的專家對這一術(shù)語進行了定義。 據(jù) Honeywell 工業(yè)測量與控制部產(chǎn)品經(jīng)理 Tom Griffiths 的定義：“一個良好的智能傳感器是由微處理器驅(qū)動的傳感器與儀表套裝，并且具有通信與板載診斷等功能，為監(jiān)控系統(tǒng)和 /或操作員提供相關(guān)信息，以提高工作效率及減少維護成本?！?無 故障通信 “智能傳感器的優(yōu)勢，” GE Fanuc 自動化公司控制器產(chǎn)品經(jīng)理 Bill Black說，“是能從過程中收集大量的信息以減少宕機時間及提高質(zhì)量?！?MTS 傳感器公司 Temposonics（磁致伸縮位移傳感器）產(chǎn)品經(jīng)理 David Edeal 對此補充說：“分布式智能的基本前提是，在適當(dāng)位置和時間擁有有關(guān)系統(tǒng)、子系統(tǒng)或組件的狀態(tài)的全部知識，以進行最優(yōu)的過程控制決策?！?Cognex 公司 Checker 機器視覺部產(chǎn)品營銷經(jīng)理 John Keating 繼續(xù)補充說，“對于一種真正的智能（機器視覺）傳感器 ，它應(yīng)該不需要使用者懂得機器視覺?！?智能傳感器必須具備通信功能?！白钇鸫a，除了滿足最基本應(yīng)用的反饋信號，智能傳感器必須能傳輸其它信息?！?Edeal 表示。這可以是疊加在標(biāo)準(zhǔn) 4-20 mA 過程輸出、總線系統(tǒng)或無線安排上的 HART（可尋址遠程傳感器高速通道的開放通信協(xié)議）信號。該領(lǐng)域正在增長的因素是 IEEE 1451 一系列旨在為不同廠家生產(chǎn)的傳感器提供即插即用能力的智能傳感器接口標(biāo)準(zhǔn)。 診斷與程序 智能傳感器可對其運行的各個方面進行自監(jiān)控，包括“攝像頭的污濁，超容忍限或不能開關(guān)等，” GE Fanuc 自動化公司的 Black 說。 Pepperl+Fuchs 公司智能系統(tǒng)經(jīng)理 Helge Hornis 補充說，“（除此之外），還有線圈監(jiān)控功能，目標(biāo)超出范圍或太近?！彼部梢詫r的變化進行補償?！爸悄軅鞲衅?，” Omron 電子有限公司戰(zhàn)略創(chuàng)意總監(jiān) Dan Armentrout 表示，“必須首先能監(jiān)視自身及周圍的環(huán)境，然后再決定是否對變化進行自動補償或?qū)ο嚓P(guān)人員發(fā)出警告?！?很多智能傳感器都能重裝到控制現(xiàn)場，通過提供“可設(shè)置參數(shù)，使用戶能替換一些標(biāo)準(zhǔn)傳感器，” Hornis 說道，“例如，典型的傳感器一般都設(shè) 置為常開（ NO）或常關(guān)（ NC），而智能傳感器則能設(shè)置為以上任何一種狀態(tài)?！?智能傳感器擁有很多優(yōu)勢。隨著嵌入式計算功能的成本繼續(xù)減少，“智能”器件將被更多地應(yīng)用。獨立的內(nèi)部診斷功能可避免代價高昂的宕機，從而迅速收回投資。 傳感器 ：越來越到位 正如人們所說的：“無論你到哪里，他都與你同在。”因為大多數(shù)的應(yīng)用仍然都要求這所表達的更高精度和更好的可重復(fù)性，所以這里介紹關(guān)于如何選擇和安裝位置傳感器的建議。 什么樣的傳感器才是對特定應(yīng)用的傳感器呢？這取決于對精度、可重復(fù)性、速度、預(yù)算、連接性、環(huán)境和位置的要求， 以及其他一些因素。你說的沒錯，選用正確的測量方法是任何成功應(yīng)用中閉合回路的第一步。 可檢測位置的傳感器技術(shù)幾乎與為機器控制和其他用途提供反饋的應(yīng)用一樣多種多樣?？臻g可能是直線的、平面的、旋轉(zhuǎn)的和三維的。在一些應(yīng)用中，它們結(jié)合使用。傳感元件同樣也是多種多樣。 DMC 公司（總部位于芝加哥的系統(tǒng)集成商）的技術(shù)總監(jiān) Ken Brey 勾畫了選擇位置傳感器的幾點選擇。 數(shù)字化思考 對數(shù)字式位置回饋： 增量型編碼器 所有的運動控制器都支持；有旋轉(zhuǎn)和直線類型以及多種解決方案；被多種其他設(shè)備仿真；當(dāng)斷電時，要求具 有回復(fù)原位過程，以實現(xiàn)為機器提供物理標(biāo)記參考。 絕對編碼器 天生就只有很少的運動控制器支持；可以用于具有足夠多可用數(shù)字輸入的控制器；在它們的范圍內(nèi)（通常是一個旋轉(zhuǎn)）可以報告完整的位置；不要求回復(fù)原位。 解算器 在焊接應(yīng)用中對高等級噪聲有很高的免疫力；在一些較大的電機中成為使用標(biāo)準(zhǔn)；當(dāng)配合恰當(dāng)?shù)乃欧糯笃魇褂脮r可模擬增量型編碼器；和一些伺服放大器共同使用可以模擬絕對編碼器。 雙編碼器反饋 通常未被充 分利用，天生地可被大部分的運動控制器支持；一個編碼器安放在電機上，另一個直接安放在負載上；當(dāng)電機和負載間的機械連接是柔性的或者是能滑動的時候，是非常有益處的。 視覺系統(tǒng) 廣泛地用于檢測，也可用于位置反饋。這樣的系統(tǒng)可在多維空間定位目標(biāo)，典型的是 X、 Y 和旋轉(zhuǎn)；通常用于查找傳送帶上的元件，目前正在提高速度和簡單易用性。 一個金屬軋制、沖壓和切割應(yīng)用提供了雙編碼反饋使用實例?！八笸ㄟ^軋機為沖壓過程快速和精確地標(biāo)定材料指數(shù)。軋機產(chǎn)生數(shù)量不一致的材料伸展和輥子滑移” Brey 解釋說。 “通過在雙回 路配置中，在輸出的材料上使用編碼器作為位置反饋和電機解算器作為速度反饋，系統(tǒng)被調(diào)節(jié)得穩(wěn)定，且單一標(biāo)定移動提供精確的標(biāo)定長度。這比先移動、后測量誤差，再不得不進行第二次校正移動要快得多，且更精確?！彼f。 有創(chuàng)造性，經(jīng)濟節(jié)約 Innoventor 公司 (密蘇里州圣路易斯市的系統(tǒng)集成商 ) 的總工程師 Sam Hammond 建議說：應(yīng)用目的決定位置傳感器的選擇；測量與反饋不應(yīng)該很復(fù)雜。“創(chuàng)造性的實施可提供簡單、經(jīng)濟的解決方案，”他說。例如，對排序問題，接近開關(guān)在許多場合可發(fā)揮很好的作用。 近來傳感器的應(yīng)用包 括在前面圖片中提到的 AGV（自動引導(dǎo)車）以及下面一些。 在一個用于密封茶葉容器頂蓋的機器中，接近開關(guān)和對射式傳感器定位靠近的包裝。 NI 公司的視覺系統(tǒng)獲得圖像并被處理，來發(fā)現(xiàn)提前印在標(biāo)簽上的條形碼的位置，然后給出恰當(dāng)?shù)碾姍C指令以實現(xiàn)理想的位置（旋轉(zhuǎn)）放置來應(yīng)用 125種標(biāo)簽類型中的一種。其中用到了兩種類型的位置傳感器。一種是簡單的感應(yīng)式接近開關(guān)，用于監(jiān)測機器狀態(tài)以確保即將發(fā)生運動的各種運動元件處于正確的位置。照相機也作為位置傳感器使用，選擇它是因為它的多目的用途、特征定位和讀條碼能力。 連續(xù)沖模（ progressive-die）沖床閉環(huán)運行。線性輸出接近開關(guān)為優(yōu)化沖模運行提供控制反饋；伺服電機在彎曲階段調(diào)整沖模位置。選用線性接近開關(guān)從金屬沖壓運行狀態(tài)給出尺寸讀數(shù)；數(shù)據(jù)用于閉環(huán)控制系統(tǒng)。 元件檢查使用激光距離測量設(shè)備來確定表面光滑度。傳感器測量返回光束的偏移，由 10 微米的尺寸即可指示出不同的表面。編碼器在距離大于 1 米的時候不能工作。選擇激光測量技術(shù)是因為它具有非常高的空間分辨率，不要求表面接觸，以及具有相當(dāng)高的距離分辨率。 汽車鑰匙和門鎖集成系統(tǒng)使用接近開關(guān)監(jiān)測在就位位置的頂蓋。與自動機械裝置一起應(yīng) 用的激光外形傳感器測量鑰匙外形。 使用什么？在哪里使用？ 傳感器供應(yīng)商認為發(fā)揮各種位置傳感技術(shù)的內(nèi)在優(yōu)勢能有利于各種應(yīng)用。 MTS 公司傳感器部的產(chǎn)品市場經(jīng)理 David Edeal 說：“對苛刻的工廠自動化環(huán)境來說，在顧客眼中最重要的因素，是產(chǎn)品的耐用性和可靠性，這甚至超過速度和精度。因此，具有內(nèi)在非接觸式傳感技術(shù)（電磁感應(yīng)、磁致伸縮、激光等）的產(chǎn)品比那些依靠物理接觸的技術(shù)（電阻式、電纜擴展等）具有非常巨大的優(yōu)勢?！?其他重要的因素是產(chǎn)品使用范圍和應(yīng)用靈活性。 Edeal 說：“換句話說，能夠適應(yīng)行程 范圍、環(huán)境條件的重大變化和能夠提供大范圍接口選擇的技術(shù)對更喜歡避免使用多種傳感器類型的客戶具有重大價值。關(guān)于這些要求，所有技術(shù)天生都有缺陷，這就是為什么會有這么多種選擇。” Edeal 暗示使某些技術(shù)適合特定應(yīng)用的高額成本帶來了一種限制，例如對線形可變差動變壓器（ LVDT）的限制?！靶谐涕L度超過 12 英尺的線性可變差動變壓器少見，因為較大的產(chǎn)品外殼（約是行程長度的兩倍）和很高的原料和制造成本。另一方面，磁致伸縮傳感技術(shù)總是要求調(diào)節(jié)電子設(shè)備。隨著微電子學(xué)的出現(xiàn)和專用集成電路的應(yīng)用，今天我們已經(jīng)前進到了這樣一點，在 相同的緊湊封裝中有多種可編程輸出類型（如模擬、編碼器和現(xiàn)場總線）可用。傳感器供應(yīng)商的關(guān)鍵是推動封裝的發(fā)展，以擴展使用范圍（優(yōu)點），同時最小化他們技術(shù)上的局限?！?聽聽你的應(yīng)用 不同的傳感器類型對不同的用途提供特有的優(yōu)點， Pepperl+Fuchs 公司的產(chǎn)品經(jīng)理 Tom Corbett 同意這一點。“有時應(yīng)用本身是需要哪一種傳感模式的決定因素。例如，在感應(yīng)區(qū)域內(nèi)的機器表面或傳送帶將意味著使用標(biāo)準(zhǔn)擴散模式傳感器與使用帶背景抑制的擴散模式傳感器會有不同。雖然標(biāo)準(zhǔn)擴散模式不能夠忽略這樣的背景目標(biāo)，但是背景抑制 模型能稍有不同地評估區(qū)別目標(biāo)表面和背景表面?！?Corbett 繼續(xù)說，“相似的，在反射應(yīng)用中，一個發(fā)亮的對象會要求使用偏振反射式的傳感器。盡管標(biāo)準(zhǔn)反射式傳感器在對準(zhǔn)一個閃亮目標(biāo)時會誤觸發(fā)，但偏振反射式采用偏振濾光片來區(qū)分發(fā)光物體和反射體?！?MTS 公司的 Edeal 說：“每一種技術(shù)都有理想的應(yīng)用，此時它容易放大它的優(yōu)點并最小化它的缺點。例如，在木材制品行業(yè)中高精度，可變行程范圍，抵抗高沖擊與振動、電磁干擾和溫度起伏的能力是非常重要的；磁致伸縮位置傳感器是線性反饋的首選。同樣，旋轉(zhuǎn)光編碼器是電機反饋的理想 適用品，因為他們具有的封裝、響應(yīng)速度、精度、耐用性和對噪聲的抵抗力。如果應(yīng)用正確，線性位置傳感器能幫助設(shè)計者在很長一段時間內(nèi)確保最佳的機器生產(chǎn)率。” 先從大范圍考慮，再縮小考慮范圍，這常常是為系統(tǒng)設(shè)計傳感器的最佳方法。Edeal 說：“傳感器的規(guī)范應(yīng)該從機器 /系統(tǒng)級的要求開始制訂，然后向后朝子系統(tǒng)級細化，最終到達元件級。這是典型的做法，但是經(jīng)常發(fā)生的是一些系統(tǒng)級的規(guī)范沒有恰當(dāng)?shù)鼗蛲暾叵蚝蠹毣g為元件要求（這并非是一件微不足道的工作）。例如，在沒有深入分析或不具備以往經(jīng)驗的情況下，機器如何運行會產(chǎn)生獨特 的或額外的環(huán)境挑戰(zhàn)（溫度、振動等）可能是不清楚的。這會導(dǎo)致在最壞的情況下過低的指定了傳感器，或者另外一種情況是應(yīng)用于保守估計的情況下，過高地指定了產(chǎn)品?！?開環(huán)還是閉環(huán) 在設(shè)計的初期，那些涉及需要決定結(jié)構(gòu)體系的因素是開環(huán)還是閉環(huán)。AutomationDirect 公司