温湿度单片机文献翻译(1)

1、简化了的湿度测量与单片机相对湿度传感器简化了的湿度测量与单片机相对湿度传感器January 1, 2013By: John Gammel, Silicon Laboratories Inc.Sensors摘 要：随着工业科技日新月异，湿度传感技术得到广泛应用。相较传统的机械湿度计现代电子湿度传感器通过吸湿材料的电容或者电阻监测湿度等相关系数的变化。相对湿度传感器实现了温度和湿度的控制。SI7005温湿度传感器采用疏水性覆盖材料，使用聚酰亚胺莫变化检测湿度变化。SI7005S集成了一个ADC，采用了非易失性存储技术， 具有一个12C接口，这种高集成度提高了耐用性和可靠性。关键词： 相对湿度；电子

2、传感器；湿度传感器1 湿度测量湿度测量变得越来越重要。本文中我们讨论单芯片的相对湿度（RH）传感器，该单片机提供了强大的性能，便携，低功耗，并且可以在各种各样的应用中实现精确的湿度检测。湿度传感技术被广泛应用于生活中：比如应用于暖通空调和制冷技术中及医疗设备的CPAP呼吸机技术中；资产跟踪和用于食品和医药等行业的存储设备，工业控制系统，气象仪器，汽车气候控制和除雾，移动计算设备。相对湿度（RH ）的测量是环境检测较困难的技术挑战。湿度感测仪器通常依赖于温度，压力，质量，一个机械，电的变化等物质，当水分被吸收，然后湿度感测仪器导出测量结果。机械湿度计在传统上用人或动物的毛发来测量湿度，因为头发的

3、长度随湿度测量发生变化。如今，现代电子湿度传感器通过测量电容或电阻或与湿气相关的变化显示湿度。相对湿度传感器，特别是那些依赖于吸湿的聚合物电介体材料的电容变化进行测量的，具有包括应用程序和使用要求：需要电路板装配过程中保护传感器，特别是在焊料回流，并需要随后补充水分传感器 需要保护传感器不受损坏或污染。在产品的生命周期中，若长时间暴露的温度或湿度传感器精度受影响，需要温度校正和线性化适用于湿度读数，其中的一些要求，源于电容式湿度传感器使用的聚酰亚胺薄膜的自然特性。其它的是传感器的开放式腔体组件暴露的管芯和传感器薄膜对环境的结果1。 CMOS的制造技术使人们有可能建立一个国家的最先进的电容式湿度

4、传感器，提供创新的，具有成本效益的封面传感元件。服用前仔细看看这些单芯片湿度传感器，让我们回顾一些相对湿度测量的基本原理。2 湿度基础在空气中发现的水蒸汽量相差很大，从接近零到饱和点。不足或过度的湿度，或在两者之间摆动时，可能会损坏敏感的材料和物体。人体使用蒸发冷却作为其主要的温度调节机制2。事实上，人类感觉到从身体而不是温度本身的热传递的速率。图1显示了相对湿度如何影响我们的舒适性。当湿度太高，汗液不易蒸发，人体可能会过热，引起不适。高温和低湿度的组合可以更有效的冷却。 露点温度相对湿度在90°F人类感知如图1。>75°F>62，Extremely uncom

5、fortable70°F-74°F52-60Quiteuncomfortable65°F-69°F44-50Somewhat uncomfortable60°F-64°F37-42，Comfortable but humid55°F-59°F1-35Comfortable50°F-54°F26-30Very comfortable<49°F<25A bit dry图1 RH水平的人类感知传统上，基于温度的控制在许多环境中已被很好地应用3。近年来，湿度的测量已经越来越重要，特

6、别是在居住，存储和制造场所。温度和相对湿度的控制对许多材料，包括药物，食品，织物和木材产品的保存是至关重要的。不可接受的湿度水平，尤其是在与极端温度相结合，显著到材料的击穿贡献。热加速恶化，以及高湿度提供水分，促进有害的化学反应。当结合时，这些因素可以鼓励昆虫活性和霉菌的生长。非常低的相对湿度也可有破坏作用，除湿敏感材料和使它们变脆。波动较大的温度和湿度也会造成损害，通过膨胀和收缩，加速恶化。准确的湿度测量控制湿度，可以防止损坏和不适，或检测到储存或运输过程中造成的产品损坏事件的重要因素。相对湿度传感必须是以可用的组件形式实现与电子控制结合及经济有效的集成4。3 测量湿度的技术湿度可以量化在许

7、多方面，但对于维持大气质量的最重要的测量是相对湿度（RH ） 。这是水蒸汽存在于空气中的实际量，这是不能吸收任何更多的水分的比率5。绝对湿度被定义为水蒸汽的质量溶解在潮湿的空气在给定温度和压力下的总体积。饱和电平通常被称为露点或霜点，这取决于相对湿度值是否可以随温度细微变化或者显著变化，在温度变化将引起相对湿度为的变化。较高的温度增加了空气中吸收水分的能力和较低的温度降低其吸收水分的能力。空气的相对湿度降低的空气被加热，当潮湿的空气被冷却时，其吸收水分的能力降低，从而导致相对湿度增加。其结果是，所需要的水蒸汽中空气的量达到使温度露点升高。10的露点，例如，对应于26相对湿度在32下。最知名的仪

8、器用于湿度测量的是干湿计，它使用“ wet-bulb/dry-bulb ”的方法6。该装置由两个温度计，一个是普通的干球（干球），另用湿布覆盖在灯泡（湿球） 。从湿布蒸发时，湿球温度计将显示的温度低于干球只要空气不饱和的水蒸汽。一个查找表被用来从两个温度读数推导出相对湿度。湿度传感器的缺点包括响应时间慢，物理尺寸精度低，确保它周围的气流良好的维护问题。用于测量当前湿度最准确的方法是冷镜湿度计。这种技术使用一个光电机制来检测缩合形成的温度控制镜面7。镜子维持在一个准确的测量温度，冷却到凝结形式。缩合散射发射LED的光，这会导致在接收光电晶体管的输出突然下降。在此凝结形成提供了可用于湿度值可以计算

9、露点温度。因为他们所需要的机械系统，冷镜湿度计仪器体积大，往往价格昂贵，不切实际的大批量消费电子、汽车和住宅应用。机械湿度计通常具有较差的精度，通常在±10的范围内。最常见的例子使用了一块动物毛发张力下保持。随着湿度的增加，头发松弛和伸展和该长度变化可以由应变仪来测量。4 电子湿度传感技术电子湿度传感器克服了许多困扰解决了旧技术的尺寸和成本的问题。最常用的技术依赖于任何的吸湿性材料的电阻或电容的改变。一种电容传感器包括由电介质材料分隔开的两个电极。典型地，如在空气中增大的水蒸汽含量，传感器的介电常数增大，改变对应于该湿度水平所测量的电容。一个电阻传感器包括一个导电层隔开的两个电极8。

10、在这种情况下，变化的湿度导致的变化的传感层的导电性。新技术用于生产薄膜，这些类型的湿度传感器准确，稳定，易于制造大量。吸湿材料的选择保证了快速的响应时间有小的滞后。例如，聚酰亚胺膜，它可以在厚度为小于5微米来制造，可以在小于10秒湿度变化的响应，同时提供良好的稳定性。电子湿度传感器的精度通常随时间漂移，通常是由温度和湿度或污染物的存在很大的差异的限制。以提高相对湿度测量的精度，这也是有效的测量温度，以提供给设备在必要时的相对湿度测量的温度补偿。以确定的露点或绝对湿度，也需要环境空气温度。例如，在测量温度1° C错误将在露点计算生产约1错误。为获得最佳精度，湿度和温度的测量，应采取尽可

11、能接近彼此，并且理想共同位于同一芯片上。这样的接近度可以是难以实现与许多传统的电子传感器的设计9。许多当今的电子传感器设计中使用分立的电阻和电容式传感器，混合，和多芯片模块。这些传统方法因材料清单（BOM）成本和元件数量大，以及需要劳动密集，客户校准高的法案。进一步的问题是，离散传感器解决方案通常是用标准不兼容的表面贴装技术（SMT ）装配流程。5 单片机传感器技术传感器必须保持清洁和完好的制造过程中，因为传感器元件必须被暴露在环境中，以执行其功能回流焊的极端热循环以及转移湿度传感器的性能，这并不总是包含在制造商的精度指标，产品的生命过程中的湿度传感器需要保护，需要使用某种类型的覆盖物或过滤器

12、，它可以阻碍传感器的响应在一些实施方式中的先进设备，在最先进的传感器解决方案10。该Si7005温湿度传感器由Silicon Labs公司解决了许多由离散，混合，模块化和湿度传感器系统所带来的设计和制造方面的挑战。该Si7005传感器采用疏水性覆盖材料，为传感器的终身保障。该温湿度传感器有膨胀聚四氟乙烯（ePTFE）的疏水性过滤器的材料制成，可以防止灰尘和液体的大部分，并且其结构允许水蒸汽通过它，以确保过滤器不会影响传感器的响应时间。因为在Si7005传感器的可选的盖被安装在工厂，没有时间或劳力花费PCB组装过程中添加和除去保护带，盖不必被设计在产品设计中。该Si7005使用的聚酰亚胺膜的变化

13、来检测湿度。此敏感薄膜被沉积在一个金属手指的电容中。精密带隙参考电路，位于同一芯片作为湿度传感器，提供温度测量。在同一裸片上检验，确保温度和湿度测量相似，提供出色的测量精度。该Si7005使用的聚酰亚胺膜的变化来检测湿度11。如果冷凝集上的传感器，芯片上的加热器可以被激活以干燥该传感器和还原操作，一旦传感器是在露点以上，管芯上的温度传感器确保微控制器（MCU ）收集的湿度读数可以采取这种加热效应。该器件的长期测量漂移由于老化是不超过0.25 RH /年。 ，这是不到许多同类竞争器件漂流的一半。指定的精度包括津贴对回流焊的影响。作为一个整体的解决方案， Si7005也是出厂时校准。该Si7005

14、需要额外的单片集成来简化系统设计，并提供更大的模块功能单一，紧凑的4毫米×4 mm QFN封装的优势。除了感测元件时， Si7005集成了一个ADC信号处理和非易失性存储器来用于校准的数据，以及一个I2C接口（图2） 。这种高集成度提高了耐用性和可靠性，降低了成本和开发时间，并简化电路板设计，也有助于降低功耗。该Si7005平的平均值， 1微安用于执行一个温度和每分钟1湿度读数。图2 Si7005湿度传感器通过使用单片集成的创新设计，该Si7005传感器带来的成本效益和精确的相对湿度和温度监测，使其在湿度监测和控制应用范围日益扩大。 参考文献 1 HU Hongbin. M

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20、rogramming language M.john wiley&sons press. 2005.180  190. Simplifying Humidity Measurement with Single-Chip Relative Humidity Sensors January 1, 2013 By: John Gammel, Silicon Laboratories Inc. SensorsAbstract: With changing industrial science and technology,

21、the humidity sensing technology is widely used. Compared with traditional mechanical hygrometer modern electronic humidity sensor by hygroscopic material capacity or resistance monitor changes in humidity, such as correlation coefficient. Relative humidity sensor for temperature and humidity control

22、. SI7005 temperature and humidity sensor is hydrophobic cover material, the use of polyimide testing humidity changes. SI7005S integrates a ADC, used the nonvolatile storage technology, with a 12 c interface, the high level of integration to improve the durability and reliability.Keywords：Relative h

23、umidity; electronic sensors; humidity sensor1 Humidity measurementHumidity measurement is increasingly important in an expanding number of industries. In this article we discuss a single-chip relative humidity (RH) sensor that offers robust performance, a small size, and low power consumption and ca

24、n enable accurate humidity sensing in a wide variety of applications.Humidity sensing technology is critical to a wide range of applications, including HVAC and refrigeration; healthcare equipment, such as CPAP machines and ventilators; asset tracking and storage devices for the food and pharmaceuti

25、cal industries; industrial control systems; meteorological instruments; automotive climate control and defogging; and mobile computing devices. Despite the number of industries and applications that require it, relative humidity (RH) measurement is among the more difficult technical challenges in en

26、vironmental sensing.Humidity sensing instruments typically rely on measurements of temperature, pressure, mass, or a mechanical or electrical change in a substance when moisture is absorbed from which the humidity can then be derived. Mechanical hygrometers (Figure 1) have traditionally used human o

27、r animal hair to measure humidity because the length of the hair changes measurably with increasing humidity. Nowadays, modern electronic humidity sensors operate by measuring the moisture-related changes in electrical capacitance or resistance or the temperature at which condensation appears1.RH se

28、nsors, in particular those that rely on measurements of the capacitance changes of hygroscopic polymeric dielectric materials, have application and usage requirements that include:The need to protect the sensor during board assembly, especially during solder reflow, and the need to subsequently rehy

29、drate the sensor.2.The need to protect the sensor from damage or contamination during the product life cycleThe potential impact on sensor accuracy of prolonged exposure to extremes of temperature and/or humidity.The need to apply temperature correction and linearization to the humidity readings.Som

30、e of these requirements stem from the natural characteristics of the polyimide films used in capacitive RH sensors. Others are a result of the sensor's open-cavity package that exposes the die and the sensor film to the environment. CMOS manufacturing techniques have made it possible to build st

31、ate-of-the-art capacitive humidity sensors that provide innovative, cost-effective covers for the sensing element. Before taking a closer look at these single-chip humidity sensors, let's review some of the basic principles of RH measurement4.2 Fundamentals of HumidityThe amount of water vapor f

32、ound in air can vary dramatically, from close to zero to the point of saturation. Insufficient or excessive humidity, or swings between the two, can damage sensitive materials and objects. The human body uses evaporative cooling as its primary temperature-regulation mechanism. In actual fact, humans

33、 feel the rate of heat transfer from the body rather than temperature itself. Figure 2 shows how the relative humidity affects our comfort. When humidity is so high that perspiration cannot easily evaporate, the body may overheat, causing discomfort. A combination of high temperature and low RH allo

34、ws more effective cooling.Figure 1. Human perception of RH levelsDew Point TemperatureRH at 90°FHuman Perception >75°F>62%Extremely uncomfortable70°F74°F52%60% Quiteuncomfortable65°F69°F44%50%Somewhat uncomfortable60°F64°F37%42%Comfortable but humid55

35、76;F59°F31%35%Comfortable50°F54°F26%30%Very comfortable<49°F<25%A bit dryTraditionally, many environments have been controlled based on temperature. In recent years, the measurement of humidity has grown in importance, especially in living, storage, and manufacturing sites.

36、 Control of temperature and RH is also critical in the preservation of many materials including medications, foods, fabrics, and wood products5.Unacceptable humidity levels, especially when combined with temperature extremes, contribute significantly to the breakdown of materials. Heat accelerates d

37、eterioration, and high RH provides moisture, which promotes harmful chemical reactions. When combined, these factors can encourage insect activity and the growth of mold. Extremely low RH can also have damaging effects, desiccating sensitive materials and causing them to become brittle. Large fluctu

38、ations in temperature and RH also cause damage through expansion and contraction, accelerating deterioration.Accurate humidity measurement is a vital part of controlling humidity to prevent damage, discomfort, or to detect events that may have caused product damage during storage or transit. For wid

39、espread use, RH sensing must be available in a component form that enables easy, cost-effective integration with electronic controls6.3 Techniques for Measuring HumidityHumidity can be quantified in a number of ways, but the most important measurement for maintaining atmospheric quality is relative

40、humidity (RH). This is the ratio of the actual water vapor present in air to the amount of water vapor present in saturated air, which cannot absorb any more moisture. Absolute humidity is defined as the mass of water vapor dissolved in a total volume of moist air at a given temperature and pressure

41、7.The saturation level is generally called the dew point or frost point, depending on the temperature. The RH value can change significantly with even slight variations in temperature; a 1°C change in temperature at 35°C and 75% RH will introduce a 4% change in RH. A higher temperature inc

42、reases the ability of air to absorb moisture and a lower temperature decreases its ability to absorb moisture. The RH of air decreases as the air is heated; when moist air is cooled, its capacity to absorb moisture decreases, causing the RH to increase. As a result, the amount of water vapor in air

43、needed to reach the dew point increases with temperature. The dew point at 10°C, for example, corresponds to a RH of 26% at 32°C.The best-known instrument for humidity measurement is the psychrometer, which uses the "wet-bulb/dry-bulb" method. The device consists of two thermomet

44、ers, one with an ordinary dry bulb and the other with a moist cloth covering the bulb (the wet bulb). As evaporation from the moist cloth occurs, the wet-bulb thermometer will show a lower temperature than the dry bulb as long as the air is not saturated with water vapor8. A look-up table is used to

45、 derive the RH from the two temperature readings. The disadvantages of a psychrometric sensor include slow response time, large physical size, and the maintenance issues of keeping one thermometer bulb wet and ensuring good airflow around it.The current most accurate method for measuring humidity is

46、 the chilled mirror hygrometer. This technique uses an optoelectronic mechanism to detect condensation that forms on a temperature-controlled mirror surface. The mirror is maintained at an accurately measured temperature and cooled until condensation forms. The condensation scatters the transmitting

47、 LED's light, which results in a sudden drop in the output of the receiving phototransistor. The temperature at which condensation forms provides the dew point from which the humidity value can be calculated. Because of the mechanical systems they require, chilled-mirror hygrometer instruments a

48、re bulky, often expensive, and impractical for use in high-volume consumer, automotive, and residential applications.Mechanical hygrometers typically exhibit poor accuracyoften in the range of ±10%. The most common example uses a piece of animal hair kept under tension. As humidity increases, t

49、he hair relaxes and stretches and this length change can be measured by a strain gauge.4 Electronic Humidity Sensing TechnologyElectronic humidity sensors overcome many of the size and cost problems that plague older techniques. The most commonly employed techniques rely either on a change in the re

50、sistance or capacitance of a hygroscopic material. A capacitive sensor consists of two electrodes separated by a dielectric material. Typically, as the water vapor content in the air increases, the sensor's dielectric constant increases, changing the measured capacitance corresponding to the hum

51、idity level. A resistive sensor consists of two electrodes separated by a conductive layer. In this case, variations in humidity result in changes in the conductivity of the sensing layer9.New techniques for producing thin films have made these types of RH sensors accurate, stable and easy to manufa

52、cture in large quantities. The choice of hygroscopic material assures fast response times with little hysteresis. For instance, a polyimide film, which can be fabricated in thicknesses of <5 µm, can respond to changes in humidity in <10 s while providing excellent stability. The accuracy

53、of an electronic RH sensor is limited by its drift over time, generally caused by wide variations in temperature and humidity or the presence of pollutants.To enhance the accuracy of RH measurements, it is also helpful to measure the temperature to provide temperature compensation for the RH measure

54、ment of the device if necessary. To determine the dew point or absolute humidity, the ambient air temperature is also required. For instance, a 1°C error in the measured temperature will produce approximately a 1°C error in the dew-point calculation. For the best accuracy, humidity and tem

55、perature measurements should be taken as close as possible to each other, and ideally co-located on the same chip. Such proximity can be difficult to achieve with many traditional electronic sensor designsMany of today's electronic sensor designs use discrete resistive and capacitive sensors, hy

56、brids, and multi-chip modules, as shown in Figure 3. These legacy approaches suffer from high bill of materials costs and component counts, large footprints, and the need for labor-intensive customer calibration10. A further problem is that discrete sensor solutions are often incompatible with stand

57、ard surface mount technology assembly flows.5 A monolithic sensor A monolithic sensor still has to contend with the following manufacturing issues:The sensor must be kept clean and undamaged during manufacturing because the sensor element must be exposed to the environment to perform its functionThe

58、 extreme thermal cycle of solder reflow can shift the performance of humidity sensors, an effect that is not always included in manufacturers' accuracy specificationsThe humidity sensor requires protection during the life of the product, requiring the use of some type of cover or filter, which c

59、an impede sensor responsiveness in some implementations.State-of-the-Art Sensor SolutionThe Si7005 temperature and humidity sensor from Silicon Labs addresses many of the design and manufacturing challenges posed by discrete, hybrid, and modular humidity sensor systems. The Si7005 sensor uses a hydrophobic cover material to provide lifelong protection for the sensor underneath. The cover, made from an expanded polytetrafluoroethylene hydrophobi