濕度傳感器系統(tǒng)畢業(yè)論文中英文資料外文翻譯

1、<p><b>　　中文2386字</b></p><p><b>　　英文:</b></p><p>　　The right design for a relative humidity sensor system</p><p>　　Optimizing the response characteristic

2、s and accuracy of a humidity sensor system</p><p>　　1 Overview</p><p>　　To make the right choice when selecting a relative humidity sensor for an application, it is important to know and to be

3、able to judge the deciding factors. In addition to long-term stability, which is a measure on how much a sensor changes its properties over time, these factors also include the measurement accuracy and the response chara

4、cteristics of the sensor. Capacitive humidity sensors are based on the principle that a humidity-sensitive polymer absorbs or releases moisture as a function o</p><p>　　Measurement accuracy</p><p&

5、gt;　　The term measurement accuracy of a humidity sensor is understood primarily to refer to the deviation of the value measured by the sensor from the actual humidity. To determine the measurement accuracy, references, s

6、uch as chilled mirror hygrometers, whose own tolerance must be taken into account, are used. In addition to this trivial component, humidity sensors require a given time for reaching stable humidity and temperature equil

7、ibrium (the humidity is a function of temperature and decreases w</p><p>　　Response characteristics and response time</p><p>　　The response characteristics are defined by various parameters. The

8、se are:</p><p>　　The actual response characteristics of the humidity sensor at constant temperature.</p><p>　　(1) How quickly the sensitive polymer absorbs or releases moisture until equilibrium

9、 is reached (intrinsic response time)</p><p>　　(2) How fast the entire system reaches humidity equilibrium (housing effect)</p><p>　　The thermal response characteristics of the humidity sensor a

10、t a non-constant temperature</p><p>　　(3) The thermal mass of the sensor</p><p>　　(4) The system's thermal mass, which is thermally coupled to the sensor (e.g. printed circuit board)</p

11、><p>　　(5) Heat sources in the direct surroundings of the sensor (electronic components)</p><p>　　(1) and (3) are determined entirely by the sensor itself, (1) primarily by the characteristics of t

12、he sensitive polymer.</p><p>　　(2) and (4) are primarily determined by the construction of the entire system (shape and size of housing andreadout circuitry).</p><p>　　(5) is determined by heat-

13、emitting electronic components.</p><p>　　These points will be discussed in more detail in the following.</p><p>　　The intrinsic response time (1)</p><p>　　Qualitatively, the respons

14、e characteristics of capacitive humidity sensors look like the following (Fig. 1).</p><p>　　Fig. 1: Typical and idealized response characteristics of capacitive humidity sensors (schematic)</p><p&

15、gt;　　Because these response characteristics are especially pronounced at high humidity values, an isothermal humidity jump from 40% to 100% was selected here for illustration. The desired ideal behavior of the sensor is

16、indicated in blue. In practice, however, the sensor behaves according to the red line, approximately according to:</p><p>　　Here, the time span 1 is usually very short (typ. 1 – 30 min.), in contrast, the ti

17、me span 2 is very long (typ. Many hours to days). Here the connection of measurement accuracy and response characteristics becomes clear (t until RH=100% is reached). The value at t4 (Fig. 1) is considered to be an exact

18、 measured value. However, this assumes that both the humidity and also the temperature remain stable during this entire time, and that the testing waits until this very long measurement time is com</p><p>　　

19、1.The measured value at t2 (Fig. 1) is used as a calibration reference.</p><p>　　Advantage:</p><p>　　The required measurement time for reaching the end value (in the example 100%) is clearly sho

20、rtened,corresponds to practice, and achieves an apparent short response time of the sensor (cf. Fig. 2).</p><p>　　Disadvantage:</p><p>　　If the conditions are similar for a long time (e.g., wet

21、periods in outdoor operation), the sensors exceed the correct end value (in the example 100%) undesirably by up to 10% (cf. Fig. 2).</p><p>　　2. The measured value at t4 (Fig. 1) is used as a calibration ref

22、erence.</p><p>　　Advantage:</p><p>　　Even for similar conditions over a long time (e.g., wet periods in outdoor operation), an exact measurement result is obtained (cf. Fig. 2).</p><p

23、>　　Disadvantage:</p><p>　　For a humidity jump like in Fig. 1, the sensors very quickly deliver the measured value at t2, but reaching a stable end value (about 3-6% higher) takes a long time (apparent lon

24、ger response time)(cf. Fig. 2).</p><p>　　In order to take into account both approaches optimally, the measured values at t3 (cf. Fig. 1) are used as the calibration reference by Sensirion AG.</p><

25、p>　　Fig. 2: Response characteristics of different humidity measurement systems</p><p>　　The housing effect on the response time (2)</p><p>　　Here, two types of transport phenomena play a deci

26、ding role:</p><p>　　Convection: For this very fast process, the air, whose humidity is to be determined, is transported to the sensor by means of ventilation.</p><p>　　Diffusion: This very slow

27、process is determined by the thermal, molecular self-motion of the water molecules. It occurs even in "stationary" air (e.g., within a housing), but leads to a long response time.</p><p>　　In order

28、 to achieve favorable response characteristics in the humidity measurement system, the very fast convection process must be supported by large housing openings and the slow diffusion process must be supported by a small

29、housing around the sensor (small "dead volume") with "stationary" air reduced to a minimum. The following applies:</p><p>　　Thermal effects (3), (4), and (5)</p><p>　　Because

30、 the total thermal mass of the humidity measurement system (sensor + housing) has a significant effect on its response time, the total thermal mass must be kept as low as possible. The greater the total thermal mass, the

31、 more inert the measurement system becomes thermally and its response time, which is temperature-dependent, increases. In order to prevent measurement errors, the sensor should not be mounted in the vicinity of heatgener

32、ating components.</p><p>　　Summary – what should be taken into account when designing a humidity measurement system</p><p>　　In order to achieve error-free operation of a humidity-measurement sy

33、stem with response times as short as possible, the following points should be taken into account especially for the selection of the sensor and for the design of the system.</p><p>　　The selection of the hum

34、idity sensor element. It should</p><p>　　● be as small as possible,</p><p>　　● have a thermal mass that is as low as possible,</p><p>　　● work with a polymer, which exhibits mini

35、mal fluctuations in measured values during the time span 2(cf. Fig. 1); testing gives simple information on this condition,</p><p>　　● provide calibration, which corresponds to the requirements (see above),

36、 e. g.,</p><p>　　SHT11/SHT15 from Sensirion.</p><p>　　The housing design (cf. Formula 1). It should</p><p>　　● have air openings that are as large as possible in the vicinity of th

37、e sensor or the sensor should be operated outside of the housing à good convection!</p><p>　　● enclose a "dead volume" that is as small as possible around the sensor à little diffusion!&

38、lt;/p><p>　　The sensor should be decoupled thermally as much as possible from other components, so that the response characteristics of the sensor are not negatively affected by the thermal inertia of the entir

39、e system.(e.g., its own printed circuit board for the humidity sensor, structurally partitioning the housing to create a small volume for the humidity sensor, see Fig. 3)</p><p>　　Fig. 3: Mounting example fo

40、r Sensirion sensors SHT11 and SHT15 with slits for thermal decoupling</p><p>　　The sensor should not be mounted in the vicinity of heat sources. If it was, measured temperature would increase and measured hu

41、midity decrease.</p><p>　　Design proposal</p><p>　　The challenge is to realize a system that operates cleanly by optimally taking into account all of the points in section 4. The already calibra

42、ted SMD humidity sensors SHT11 and SHT15 from Sensirion are the ideal solution. For optimum integration of the sensors in a measurement system, Sensirion AG has also developed a filter cap as an adapter aid, which takes

43、into account as much as possible the points in section 4 and also protects the sensor against contaminants with a filter membrane. Fig. 4</p><p>　　Fig. 4: Filter cap for SHT11 and SHT15</p><p>　

44、　In addition to the advantages mentioned above, there is also the option of building an IP67-compatible humidity measurement device (with O-ring, cf. Fig. 4) with optimal performance. Detailed information is available on

45、 the Sensirion Web site.</p><p><b>　　譯文：</b></p><p>　　相 對(duì) 濕 度 傳 感 器 系 統(tǒng) 的 正 確 設(shè) 計(jì)</p><p>　　濕度傳感器系統(tǒng)精度及響應(yīng)特性的優(yōu)化</p><p><b>　　綜述</b></p><p

46、>　　為了在相對(duì)濕度的應(yīng)用方面對(duì)傳感器做出正確的選擇，了解和評(píng)估那些起決定作用的因素是非常重要的。除了衡量傳感器性能隨時(shí)間變化而變化的長(zhǎng)期穩(wěn)定性這個(gè)因素以外，還應(yīng)考慮傳感器的測(cè)量精度和響應(yīng)特性這兩個(gè)因素。電容式濕度傳感器工作是基于這樣一個(gè)原理；其濕敏聚合體元件能吸收或釋放濕氣被看作是與周圍環(huán)境濕度相關(guān)的一項(xiàng)功能，由于這種方法僅僅測(cè)量了傳感器所在位置這一點(diǎn)的濕度，而通常是要測(cè)量其周圍濕度這個(gè)數(shù)值，所以傳感器必須在周圍環(huán)境濕度平衡的狀

47、態(tài)下獲得精確的測(cè)量值（參</p><p>　　照“響應(yīng)時(shí)間的殼體（1）效應(yīng)”這一部分）。這個(gè)濕度平衡過(guò)程可以通過(guò)各種用時(shí)間常數(shù)表征的傳輸現(xiàn)象得以實(shí)現(xiàn)。測(cè)量精度和響應(yīng)時(shí)間是如此地接近并且相互依賴，使?jié)穸葴y(cè)量系統(tǒng)的結(jié)構(gòu)設(shè)計(jì)成為一項(xiàng)挑戰(zhàn)。</p><p><b>　　測(cè)量精度</b></p><p>　　濕度傳感器的測(cè)量精度這個(gè)術(shù)語(yǔ)主要用于表述濕度傳

48、感器的測(cè)量值與實(shí)際濕度之間的偏差值。要確定測(cè)量精度，應(yīng)參考使用冷鏡式濕度計(jì)，同時(shí)必須考慮冷鏡自身的誤差范圍。除了這個(gè)微不足道的部件以外，濕度傳感器還需要給定一個(gè)達(dá)到濕度與溫度穩(wěn)定平衡的時(shí)間。（濕度是溫度的函數(shù)，濕度會(huì)隨著溫度升高而降低，傳感器與被測(cè)環(huán)境之間的溫差會(huì)導(dǎo)致濕度測(cè)量誤差）更詳細(xì)的說(shuō)明請(qǐng)見(jiàn)下一節(jié)。</p><p>　　3．響應(yīng)特性和響應(yīng)時(shí)間</p><p>　　響應(yīng)特性的各種定義：

49、</p><p>　　恒溫狀態(tài)下濕度傳感器的實(shí)際響應(yīng)特性：</p><p>　　1. 濕敏聚合體吸收或釋放濕氣達(dá)到濕度平衡狀態(tài)時(shí)的時(shí)間快慢。（固有的響應(yīng)時(shí)間）</p><p>　　2. 整個(gè)系統(tǒng)到達(dá)濕度平衡時(shí)所需要的時(shí)間快慢。（殼體效應(yīng)）</p><p>　　非恒溫狀態(tài)下濕度傳感器的熱響應(yīng)特性</p><p>　　3.

50、 傳感器的熱質(zhì)量。</p><p>　　4. 與傳感器相關(guān)的系統(tǒng)熱質(zhì)量。（例如印刷線路板的結(jié)構(gòu)影響）</p><p>　　5. 傳感器周圍的直接熱源。（例如電子元器件發(fā)熱影響）</p><p>　　1 和3 完全取決于傳感器自身特性。1 主要取決于敏感聚合體的特性。</p><p>　　2 和4 主要取決于整個(gè)系統(tǒng)的結(jié)構(gòu)設(shè)計(jì)。（殼體的形狀和尺

51、寸設(shè)計(jì)以及輸出電路設(shè)計(jì)）5 取決于電子元器件的發(fā)熱量。</p><p>　　以上幾點(diǎn)將在下面做詳細(xì)討論；</p><p><b>　　固有的響應(yīng)時(shí)間1</b></p><p>　　電容式濕度傳感器的時(shí)間響應(yīng)特性看起來(lái)就和下面圖1 所示一樣</p><p>　　圖 1 典型的和理想的電容式濕度傳感器響應(yīng)特性（示意圖）<

52、;/p><p>　　由于在高濕階段其響應(yīng)特性表現(xiàn)的特別明顯，故選擇了濕度從40%RH 到100%RH 的等溫階躍來(lái)說(shuō)明。所期望的傳感器的理想響應(yīng)特性用藍(lán)色虛線表示，而實(shí)際的響應(yīng)特性用紅線表示，其近似公式為：</p><p>　　這里，時(shí)間段1 通常非常短（大約1--30 分鐘）。相比之下時(shí)間段2 是很長(zhǎng)很長(zhǎng)的，（數(shù)小時(shí)至數(shù)天），測(cè)量精度與響應(yīng)特性的關(guān)系在這張圖上看得更清晰了（t 延續(xù)到濕度達(dá)到

53、100%RH 時(shí)為止）。t4 時(shí)間所對(duì)應(yīng)的測(cè)量值是非常精準(zhǔn)的。無(wú)論如何，得假定在整個(gè)t4測(cè)試時(shí)間段內(nèi)濕度和溫度都要保持穩(wěn)定并且等候完成測(cè)試所需要的時(shí)間也很長(zhǎng)。在實(shí)踐中這些不尋常的工作條件是很難實(shí)現(xiàn)的。實(shí)際的校準(zhǔn)工作通常用以下兩種方法（參見(jiàn)圖2）：</p><p>　　1. 以t2 時(shí)間對(duì)應(yīng)的測(cè)量值作為校驗(yàn)參考基準(zhǔn)；</p><p><b>　　優(yōu)點(diǎn)：</b></

54、p><p>　　到達(dá)終端值（例如100%RH）所需要的測(cè)量時(shí)間明顯地縮短了，對(duì)應(yīng)于實(shí)際上的快速響應(yīng)傳感器。（參考圖2）</p><p><b>　　缺點(diǎn)</b></p><p>　　如果相類似的條件長(zhǎng)時(shí)間不變，（例如雨季時(shí)在戶外測(cè)量）傳感器的測(cè)量值將超過(guò)校準(zhǔn)參考點(diǎn)（100%RH）令人遺憾地達(dá)到110%RH。 （參考圖2）</p>&l

55、t;p>　　2. 以t4 時(shí)間（參考圖1）對(duì)應(yīng)的測(cè)量值作為校驗(yàn)參考基準(zhǔn)；</p><p><b>　　優(yōu)點(diǎn)：</b></p><p>　　應(yīng)用于相類似的條件且長(zhǎng)時(shí)間不變，（例如雨季時(shí)在戶外測(cè)量），可以得到精準(zhǔn)的測(cè)量結(jié)果。（參考圖2）</p><p><b>　　缺點(diǎn)</b></p><p>　

56、　對(duì)于像圖1 那樣的濕度躍升，傳感器會(huì)很快在t2 時(shí)間達(dá)到相應(yīng)的測(cè)量值。但是，要到達(dá)距其還有3%RH -- 6%RH的終端測(cè)量值還需要很長(zhǎng)的時(shí)間。（顯然其響應(yīng)時(shí)間更長(zhǎng)，參考圖2）</p><p>　　綜合以上兩種處理方法的優(yōu)點(diǎn)，Sensirion AG 采用t3時(shí)間（參考圖1）對(duì)應(yīng)的測(cè)量值作為校驗(yàn)參考基準(zhǔn)。</p><p>　　圖2. 不同測(cè)量系統(tǒng)的響應(yīng)特性</p><

57、p>　　響應(yīng)時(shí)間的殼體效應(yīng)（2）</p><p>　　在這里有兩種傳輸現(xiàn)象扮演重要的角色。</p><p>　　對(duì)流：這是個(gè)很快的過(guò)程，空氣中被測(cè)量的濕氣是利用通風(fēng)的方法實(shí)現(xiàn)傳輸?shù)摹?lt;/p><p>　　傳導(dǎo)：這是個(gè)很慢的由水分子的分子熱運(yùn)動(dòng)決定的過(guò)程，它出現(xiàn)在“靜止的”空氣中（例如在殼體內(nèi)部），使響應(yīng)時(shí)間變長(zhǎng)。</p><p>　　要

58、在濕度測(cè)量系統(tǒng)中獲得良好的響應(yīng)特性，必須增大殼體開(kāi)孔以得到快速的對(duì)流，同時(shí)努力減小傳感器周圍“靜止的”空間（即減小“死區(qū)”）。以下公式適用：</p><p>　　熱影響（3）、（4）及（5）</p><p>　　由于濕度測(cè)量系統(tǒng)（傳感器+殼體）總的熱質(zhì)量對(duì)其響應(yīng)特性有著重要的影響，所以設(shè)計(jì)時(shí)必須盡可能地減小其熱質(zhì)量。測(cè)量系統(tǒng)逐漸變熱，受溫度影響的的系統(tǒng)響應(yīng)時(shí)間就會(huì)增加；系統(tǒng)總熱質(zhì)量越大，其

59、惰性也越大。為了防止附加的測(cè)量誤差，傳感器不要安裝在發(fā)熱的電子元器件附近。</p><p>　　4 . 總結(jié)—設(shè)計(jì)濕度測(cè)量系統(tǒng)時(shí)應(yīng)該考慮的問(wèn)題</p><p>　　為了實(shí)現(xiàn)濕度測(cè)量系統(tǒng)的無(wú)誤差運(yùn)行，系統(tǒng)的響應(yīng)時(shí)間應(yīng)盡可能的短。以下幾點(diǎn)在選擇系統(tǒng)傳感器時(shí)應(yīng)當(dāng)引起特別注意：</p><p>　　所選擇的濕度傳感元件應(yīng)該是：</p><p>　　●

60、 幾何尺寸越小越好</p><p>　　● 其熱質(zhì)量越小越好</p><p>　　● 具有濕敏聚合體結(jié)構(gòu)；其在時(shí)間段2 上的測(cè)量值波動(dòng)極小(參考圖1)，在測(cè)試條件下能提供簡(jiǎn)單的測(cè)試報(bào)告。</p><p>　　● 能提供校準(zhǔn)以對(duì)應(yīng)上述的各種需求，就像Sensirion SHTXX 系列傳感器所能提供的那種校準(zhǔn)。</p><p>　　殼體設(shè)計(jì)(參

61、考公式1)應(yīng)考慮：</p><p>　　● 傳感器周圍空氣流通口的尺寸要盡可能地大，或者直接將傳感器置于殼外 → 對(duì)流性最好封入套管內(nèi)時(shí)傳感器周圍的“死區(qū)”要盡可能地小，→ 傳導(dǎo)性最小。</p><p>　　傳感器應(yīng)盡可能地減少與其它元器件的熱連接，只有這樣整個(gè)系統(tǒng)的熱慣性才不至于對(duì)其響應(yīng)特性產(chǎn)生負(fù)面作用。（例如：印刷線路板被分隔成很小的一個(gè)體積來(lái)支撐傳感器。見(jiàn)圖3）</p>

62、<p>　　圖3 Sensorion SHT1X 系列傳感器帶有減少熱連接的縫隙的安裝設(shè)計(jì)舉例</p><p>　　傳感器絕不要安裝在熱源附近。那樣會(huì)導(dǎo)致被測(cè)溫度比實(shí)際溫度高，而濕度則降低的結(jié)果。</p><p><b>　　5. 設(shè)計(jì)指南</b></p><p>　　要實(shí)現(xiàn)一個(gè)操作簡(jiǎn)捷的濕度測(cè)量系統(tǒng)，應(yīng)充分考慮到第4 部分的所有重