原文：
编者语：在流程工业中，阀门和驱动器用于液体流动的控制和转移。越来越多的工厂工程师希望在控制系统中得到阀门、龙头及驱动器当下位置的反馈信号。通常这种信号由内置于开关盒中的接近传感器，或直接安装在驱动器或手动阀门上的双传感器来获取。本文深入探讨在现场和市场新趋势中应用的传感器类型。 　　标准化现状 　　行业标准对于技术的发展而言利弊共存。一方面，它限制了创造性，但另一方面他们又确保了不同制造商的设备具备兼容性。VDE / VDI3845标准要求了诸多事项后，规定了气动驱动器与所连接设备之间的重要机械连接。该标准包括了对安装孔的定义：30×80mm和30×130mm。安装杆的高度为20、30和50mm。对于安装杆直径，则没有固定的标准，所以在双传感器的应用中，用户必须特别注意。 　　开关盒 　　“开关盒”通常描述在一个封闭盒中传感器、凸轮和连接器的集成。 传感器和气动执行器通过它实现机械连接。该解决方案旨在避免传感器在周边环境中的暴露或受到影响，同时能够使用标准传感器（见上图）。在这些标准开关盒中，典型内置以下传感器： 　　圆柱型传感器，典型长度为40mm； 　　槽形传感器； 　　矩形V3风格传感器（类似于微动开关）； 　　双传感器，结构紧凑置于一个盒中； 　　印刷电路板解决方案。 　　开关盒被用作终端设备来连接阀位传感器和电磁阀。编码的连接器以及必要的LED指示灯已经置于电路板上。电路板的尺寸适合大多数标准盒子。 　　开放式解决方案 　　“开放式解决方案”规定了自动阀或手动阀上的双传感器安装。两个电感式传感器叠加安装于一个外壳中，xx显示了阀门的开关位置。 　　该系统的设计考虑了VDE / VDI 3845标准。这些传感器由两个90°垂直安装于“圆盘”上的不锈钢目标触发。圆盘本身通过一个螺丝钉安装在执行器上。 　　除了体积小巧，组装简单，我们还发现以下优点： 　　传感器外壳上的圆形安装孔（非槽形）可避免由于错误的安装距离或运动而导致的碰撞或震动引起的维修。 　　两个开关元件（圆盘）可以适应多种不同的气动执行器。惟一需要做出的选择是安装模式，例如： 30×80mm或30×130mm。 　　不锈钢的目标物已经设计在圆盘上。 　　4个LED灯表明该传感器的输出情况，电源有无和电磁阀输出状态。 　　双传感器的检测区域足够狭窄，因而不会产生挤压点导致操作人员受伤，或冰块、灰尘形成的堵塞。 　　电磁阀的接线，可经过传感器进行布线，现场无需单独电缆。 　　电感式传感器与机械开关 　　在所有的工业领域中，机械开关曾经一度是各种控制问题的方案{sx}，而如今的方法已今非昔比，传感器毋庸置疑为{sx}。因为传感器的工作速度和可靠性的优势十分明显： 　　全固态，因此无磨损或误差修改； 　　快速输出开关状态； 　　磁滞和重复性可以比机械设备更多的进行电子定义； 　　无焊接或输出端腐蚀； 　　很少或根本不受堵塞或湿度的影响； 　　无触点抖动（输出回波）； 　　大多数传感器切换时有LED显示。使得维护和调试更简单，快捷。 　　通常，一个电感式传感器的平均寿命大大超过机械开关。事实上，过去很多机械开关都用于阀门反馈是由于低廉的价格，同时也因为我们在使用开关时极性问题不需要考虑。通过现代技术，倍加福已经成功地将传感器推向市场，xx了机械式开关仅有的一点优势。 　　用于阀位检测的传感器 　　选择正确的传感器可按以下4个简单步骤实现： 　　步骤1：开关盒或还是开放式解决方案？ 　　权衡上述优势与缺点，做出选择。您可能需要开关盒的保护，或开放式解决方案的简单便捷。大多数阀门供应商都会提供两种解决方案。你会发现开关盒的体积和重量都各异，数量与种类也大相径庭。 　　步骤2：电气定义传感器的终端，传感器所连接的控制系统调节着工作过程（交流，直流，Namur等）。极为重要的一点是该系统是否在易燃易爆区域使用。我们看以下的电气连接类型。 　　直流三线传感器。这些传感器在两条供电线路外还有一条单独的线路。第三条线路连接到PLC输入卡或控制系统上的输出端。 　　直流两线传感器。在这里，负载与传感器串联。许多传感器都具备极性容差，即无需再关心接线的极性。因此，它与连接正常的机械开关一样简单。实际应用这类传感器，您一定要注意电路的漏电流及传感器的电压降。 　　带有常开（NO）和/或常闭输出的交流传感器。在这里，负载与传感器串联。 　　交直流两线通用传感器。该传感器与负载串联。无论交流电压或直流电压均可连接。 　　两线Namur传感器，与相关本安产品一起，用于防爆环境（区域0，1和2）。可实现断线及短路监测。 　　两线故障安全传感器。按两线Namur传感器标准，但是使用满足安全级别的隔离栅，可以达到SIL3 安全等级。 　　步骤3：连接的可能性 　　连接方式取决于最终用户。例如，带电缆的密封管或插头。化学和制药领域倾向于选择电缆连接，通过电缆密封管进入盒子或传感器。 　　步骤4：电磁阀操作 　　与开关盒一样，使用双传感器也可以经过传感器进行电磁阀的布线，其优势就在于执行器只需要一根电缆连接。 　　{zh1}，您必须确认传感器的诸多特性以确保传感器在应用中xx运行。 　　类似的例子便是漏电流、电压降，周围环境，{zd0}输出电流和工作电压。 如果可能，您可以通过选定传感器的规格来确认，保证在静态电流（干扰）冲击和振动{zd0}值的允许范围内。 　　未来的发展 　　由于安装过程经常要适应{zx1}的技术发展，以提高工作效率和稳定性，各种总线系统开始进入市场。 　　开关盒和执行器的生产商当然希望加入。我们看到许多这样的制造商已经与传感器制造商协商开发出了这些总线系统的接口。带AS-i的开关盒便是一个很好的例子，因为这种总线系统特别适合数字信息。如果最终用户希望使用标准传感器，便需要合适的现场安装模块，如AS-interface，Profibus PA或基金会现场总线。 　　另一方面，我们也看到使用带有Profibus或基金会现场总线接口的电气执行器和定位系统。显然越来越多的公司意识到总线系统的优势，特别是带AS-i的现场总线组合（如Profibus）十分多见。 　　结论：我们越来越多感受到电感式传感器取代机械开关的趋势。在某些市场，60%~70%装有电感式开关的开关盒已取代了机械式开关。阀位检测的标准化还有一段路要走。这是因为原来开关盒设计的起点中机械装配和开关技术大量混合存在着。更常见的是，最终用户也经常要求提供更为可靠的解决方案，着眼于开关盒的长期回报。 　　在某些行业领域中，开放式解决方案是一个明显的趋势，因为它的价格很接近于机械接触的开关盒方案。现在由于开放式解决方案的尺寸和成本的优势，在手动阀上装配位置反馈也变得更有吸引力。

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译文：
Editor's Words: In the process industry, valves and actuators for fluid flow control and transfer. More and more plant engineers hope to get the valve control system, the leading position and drive current feedback signal. Usually the signal from the built-in proximity sensor switch box, or directly installed in the drive or manual valve on the two-sensor to obtain. This depth of market trends in the field and the application of sensor types. Standardization Status Industry standards for technology development, advantages and disadvantages. On the one hand, it limits creativity, but on the other hand they ensure the equipment of different manufacturers to be compatible. VDE / VDI3845 standards require a lot of matter, the provisions of the pneumatic drive is connected with the important mechanical connection between devices. The standard includes the definition of the mounting hole: 30 × 80mm and 30 × 130mm. Install bar height 20,30 and 50mm. For installation diameter, there is no fixed standard, so double-sensor applications, the user must pay special attention. Switch Box "Switch Box" usually describes the sensor in a closed box, cam and integrated connector. Sensors and pneumatic actuators to achieve through its mechanical connection. The solution to avoid the sensor exposed in the surrounding environment or be affected at the same time be able to use the standard sensor (see above). In these standard switch box, the typical built-in the following sensors: Cylindrical sensor, the typical length of 40mm; Slot sensors; V3 rectangular style sensors (similar to the micro switch); Dual sensor, compact and placed in a box; Printed circuit board solutions. Switch box is used as terminal equipment to connect to valve position sensor and solenoid valve. Coded connectors and LED indicator light has been necessary to put on the board. Board for most standard size box. Open Solutions "Open solution" provides an automatic valve or manual valve on the two-sensor installation. Superposition of the two inductive sensors installed in a shell, the accurate display of the valve closed position. The system design considerations of the VDE / VDI 3845 standards. The sensor consists of two 90 ° vertical installation in the "disk" on the stainless steel target trigger. Disc itself is installed via a screw actuator. In addition to small size, simple assembly, we also find the following advantages: Sensor housing on the round mounting holes (non-groove) can avoid the installation error due to distance or movement or vibration caused by collision repair. 2 switching elements (disk) can be adapted to different pneumatic actuators. Only need to make the choice to install mode, for example: 30 × 80mm or 30 × 130mm. Stainless steel target has been designed in the disk. 4 LED light indicates that the sensor output condition, power availability and solenoid valve output state. Two-sensor detection area narrow enough, and thus will not produce compression point lead to operator injury or ice and dust formed plug. Solenoid valve terminal can read the sensor cabling, on-site without a separate cable. Inductive sensors and mechanical switches In all industrial areas, Mechanical switch once the various control programs is preferred, but not what today's method, the sensor is no doubt the first choice. Because of the sensor speed and reliability of the advantages are clear: All solid-state, therefore, no wear or error modification; Fast output switch state; Hysteresis and repeatability can be more than the mechanical equipment for electronic definition; No welding or corrosion output; Little or no effect from blocking or humidity; Non-contact jitter (output echo); When most of sensors switch LED display. Makes maintenance and debugging easier and faster. Typically, an inductive transducer, the average life expectancy far exceeds mechanical switch. In fact, over the past number of mechanical switches are used for valve feedback is due to low prices, but also because we do not need to use the switch polarity issue to consider. Through modern technology, Pepperl and Fuchs Sensors have been successfully to market, eliminates the mechanical advantage of the little switch. Valve position sensor for the detection of Select the correct sensor can achieve the following four simple steps: Step 1: switch boxes or still open solution? Weigh the advantages and disadvantages to choose. You may need to switch box for protection, or open a simple and convenient solution. Most valve suppliers will provide two solutions. Switch box you will find the volume and weight are different, the number and types are quite different. Step 2: definition of the sensor electrical terminals, sensors connected to the process control system for regulating the work of (AC, DC, Namur, etc.). Very important point is whether the system used in explosive areas. We see the following types of electrical connections. DC three-wire sensor. These sensors have two external power lines of a single line. Third line connected to the PLC input card or control the output of the system. DC two-wire sensor. Here, the load in series with the sensor. Many sensors have the polarity of tolerance, that is no longer concerned about the wiring polarity. Therefore, it is normally connected as simple mechanical switches. Practical application of these sensors, you must pay attention to the leakage current and the sensor circuit voltage drop. With normally open (NO) and / or normally closed output AC transducer. Here, the load and sensor series. Universal AC-DC 2 wire sensor. The sensor in series with the load. Whether AC voltage or DC voltage may be connected. Two lines Namur sensors, and related products with the security for the explosion-proof environment (region 0,1 and 2). Break and short circuit monitoring can be realized. Fail-safe two-wire sensors. Namur sensor according to the standard two-wire, but the use to meet the security level of the fence, you can achieve SIL3 level of security. Step 3: Connect the possibility of Connection depends on the end user. For example, with cable gland or plug. Chemical and pharmaceutical fields tend to choose cable connection, through the cable box or a sealed tube into the sensor. Step 4: solenoid valve operation As with the switch box, use two sensors can also be carried out through the valve sensor cabling, its advantage is that the actuator need only one cable connection. Finally, you must confirm many features of the sensor to ensure the sensor in the application perfectly. A similar example is the leakage current, voltage drop, the environment, the maximum output current and voltage. If possible, you can select the sensor specifications to verify and ensure the quiescent current (Interference) Shock and vibration maximum allowable range. Future development As the installation process often to adapt to the latest technological developments to improve efficiency and stability, various bus systems on the market. Switch boxes and actuator manufacturers certainly want to join. We see many of these manufacturers have in consultation with the sensor manufacturers to develop these bus system interface. With AS-i switch box is a good example, because the bus system especially suited to digital information. If end users want to use standard sensors, they need the right site installation module, such as AS-interface, Profibus PA or Foundation Fieldbus. On the other hand, we also see the use with Profibus or Foundation Fieldbus interface electrical actuators and positioning systems. Clearly more and more companies realize the advantages of the bus system, especially with AS-i field bus combinations (such as Profibus) is more common. Conclusion: We feel more and more inductive sensors replace mechanical switches in the trend. In some markets, 60% to 70% with inductive switch the switch box has been replaced by a mechanical switch. Standardized test valve position is still some way to go. This is because the starting point of the original design of switch boxes and switch technology in the mechanical assembly there is a lot of mixing. More often, end users are often asked to provide a more reliable solution, focusing on the switch box of long-term returns. In some industries, the open-ended solution is a clear trend, because its price is very close to the mechanical contact of the switch box program. Now that the open solution size and cost advantages in the assembly manual valve position feedback is also more attractive.