勇闖新世界︰ W!o《卡夫卡村》變形祭︰感知自然‧尖端‧四

假使我們閱讀

LPS25H 的『數據表』 Data Sheet ︰

Description

The LPS25H is an ultra compact absolute piezoresistive pressure sensor. It includes a monolithic sensing element and an IC interface
able to take the information from the sensing element and to provide a digital signal to the external world.

The sensing element consists of a suspended membrane realized inside a single mono-silicon substrate. It is capable to detect the absolute pressure and is manufactured with a dedicated process developed by ST.

The membrane is very small compared to the traditionally built silicon micromachined membranes. Membrane breakage is prevented
by an intrinsic mechanical stopper.

The IC interface is manufactured using a standard CMOS process that allows a high level of integration to design a dedicated circuit which is trimmed to better match the sensing element
characteristics.

The LPS25H is available in a cavity holed LGA package (HCLGA). It is guaranteed to operate over a temperature range extending from -30 °C to +105 °C. The package is holed to allow external pressure to reach the sensing element.

Key Features

260 to 1260 mbar absolute pressure range
High-resolution mode: 1 Pa RMS
Low power consumption:
Low resolution mode: 4 μA
High resolution mode: 25 μA
High overpressure capability: 20x full scale
Embedded temperature compensation
Embedded 24-bit ADC
Selectable ODR from 1 Hz to 25 Hz
SPI and I²C interfaces
Embedded FIFO
Supply voltage: 1.7 to 3.6 V
High shock survivability: 10,000 g
Small and thin package
ECOPACK® lead-free compliant

，或好奇於『壓阻效應』 Piezoresistive effect

壓阻效應是用來描述材料在受到機械式應力下所產生的電阻變化。不同於壓電效應，壓阻效應只產生阻抗變化，並不會產生電荷。

要如何用來量測『大氣壓力』？也許引用一段圖文將能解惑的耶！

8.4.5 Pressure Microsensors

Pressure microsensors were the first type of silicon micromachined sensors to be developed in the late 1950s and early 1960s. Consequently, the pressure microsensors represent probably the most mature silicon micromechanical device with widespread commercial availability today. ……

Figure 8.27 Basic types of silicon pressure sensors based on a vertical deflection: (a) piezoresistive (polysilicon) and (b) capacitive (single-crystal silicon)

The two most common methods to fabricate pressure microsensors are bulk and surface micromachining of polysilicon. Silicon diaphragms can be made using either technique as described earlier. Figure 8.27 illustrates the basic principles of a piezoresistive sensor
and a capacitive pressure sensor.

The deflection in the diaphragm can be measured using piezoresistive strain gauges located in the appropriate region of maximum strain, as shown in Figure 8.27(a). The strain gauges are usually made from doped silicon and are designed in pairs with a read-out circuit such as a Wheatstone bridge. The change in strain can be related to the applied pressure ( $P - P_0$ ) and stored in a lookup table. The precise relationship depends on the relevant piezoresistive coefficient $\Pi$ of the diaphragm material.

$V_{out} \propto \ \Delta R \ \propto \Pi ( P - P_0 )$ (8.32)

A single crystal of silicon is a desirable material to use for the diaphragm because neither creep nor hysteresis occurs. The piezoresistive constant ( $\Pi$ ) is typically +138.1 pC/N
and that makes measuring pressure in the range of 0 to 1 MPa relatively straightforward.

Figure 8.27(b) shows the general arrangement of a single-crystal silicon pressure sensor with capacitive pickup. In this case, a capacitive bridge can be formed with two reference capacitors and the output voltage is related to the deflection of the membrane $\Delta x$ and hence the applied pressure ( $P - P_0$ ).

$V_{out} \propto \ \Delta C \propto \ \Delta x \propto \ (P - P_0)$ (8.33)

In this case, the accurate positioning of the pickup electrodes is crucial. By controlling the background pressure $P_0$ , it is possible to fabricate the following basic types of pressure sensors:

• An absolute pressure sensor that is referenced to a vacuum ( $P_0 = 0$ )

• A gauge-type pressure sensor that is referenced to atmospheric pressure ( $P_0 = 1 \ atm$ )

• A differential or relative type ( $P_0$ is constant).

─── 引自

《 Microsensors, MEMS, and Smart Devices 》

by
Julian W. Gardner
University of Warwick, UK
Vijay K. Varadan
Osama O. Awadelkarim
Pennsylvania State University, USA ───

既然是以某種的『機械結構』所構造，即使製作得很小，還是符合『物理力學』之原理。若是缺乏適當的『避震設計』，依舊免不了『振動』與『突波』的影響。所以『數據表』方才特別強調『 High shock survivability 』的乎？下面的實測結果︰

【不施加搖晃振動】

pi@raspberrypi ~  sudo python3
Python 3.2.3 (default, Mar  1 2013, 11:53:50) 
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import time
>>> from sense_hat import SenseHat
>>> 感測 = SenseHat()
>>> while True:
...     壓力 = 感測.get_pressure()
...     print("Pressure: %s Millibars" % 壓力)
...     time.sleep(3)
... 
Pressure: 1012.3779296875 Millibars
Pressure: 1012.384765625 Millibars
Pressure: 1012.3642578125 Millibars
Pressure: 1012.353515625 Millibars
Pressure: 1012.378173828125 Millibars
Pressure: 1012.34765625 Millibars
Pressure: 1012.355224609375 Millibars
Pressure: 1012.345703125 Millibars
Pressure: 1012.364501953125 Millibars
Pressure: 1012.3623046875 Millibars
Pressure: 1012.36083984375 Millibars
Pressure: 1012.396484375 Millibars
Pressure: 1012.35693359375 Millibars
Pressure: 1012.397216796875 Millibars
Pressure: 1012.357177734375 Millibars
Pressure: 1012.398681640625 Millibars
Pressure: 1012.39697265625 Millibars
Pressure: 1012.390380859375 Millibars
Pressure: 1012.403564453125 Millibars
Pressure: 1012.377685546875 Millibars
Pressure: 1012.358154296875 Millibars
^CTraceback (most recent call last):
  File "<stdin>", line 4, in <module>
KeyboardInterrupt
>>>

或可驗證所說矣。如是我們是否更加明白所謂『機電整合』是何事的呢？清楚知道『學科融匯』是進入未來科技世界之『通行證』的嗎？？或將理解『【Sonic π】…… 』一大系列文本所談之事乎！

清‧劉鶚‧《老殘遊記》

第二回　歷山山下古帝遺蹤　明湖湖邊美人絕調
…
停了數分鐘時，簾子裡面出來一個姑娘，約有十六七歲，長長鴨蛋臉兒，梳了一個抓髻，戴了一副銀耳環，穿了一件藍布外褂兒，一夫朗和斐條藍布褲子，都是黑布鑲滾的。雖是粗布衣裳，到十分潔淨。來到半桌後面右手椅子上坐下。那彈弦子的便取了弦子，錚錚鏦鏦彈起。這姑娘便立起身來，左手取了梨花簡，夾在指頭縫裡，便丁丁當當的敲，與那弦子聲音相應。右手持了鼓捶子，凝神聽那弦子的節奏。忽羯鼓一聲，歌喉遽發，字字清脆，聲聲宛轉，如新鶯出谷，乳燕歸巢，每句七字，每段數十句，或緩或急，忽高忽低。其中轉腔換調之處，百變不窮，覺一切歌曲腔調俱出其下，以為觀止矣。

旁坐有兩人，其一人低聲問那人道：「此想必是白妞了罷？」其一人道：「不是。這人叫黑妞，是白妞的妹子。他的調門兒都是白妞教的，若比白妞，還不曉得差多遠呢！他的好處人說得出，白妞的好處人說不出；他的好處人學的到，白妞的好處人學不到。你想，這幾年來，好玩耍的誰不學他們的調兒呢？就是窯子裡的姑娘，也人人都學，只是頂多有一兩句到黑妞的地步。若白妞的好處，從沒有一個人能及他十分裡的一分的。」說著的時候，黑妞早唱完，後面去了。這時滿園子裡的人，談心的談心，說笑的說笑。賣瓜子、落花生、山裡紅、核桃仁的，高聲喊叫著賣，滿園子裡聽來都是人聲。

正在熱鬧哄哄的時節，只見那後臺裡，又出來了一位姑娘，年紀約十八九歲，裝束與前一個毫無分別。瓜子臉兒，白淨麵皮，相貌不過中人以上之姿，只覺得秀而不媚，清而不寒。半低著頭出來，立在半桌後面，把梨花簡了當了幾聲。煞是奇怪，只是兩片頑鐵，到他手裡，便有了五音十二律以的。又將鼓捶子輕輕的點了兩下，方抬起頭來，向臺下一盼。那雙眼睛，如秋水，如寒星，如寶珠，如白水銀裡頭養著兩丸黑水銀，左右一顧一看，連那坐在遠遠牆角子裡的人，都覺得王小玉看見我了，那坐得近的更不必說。就這一眼，滿園子裡便鴉雀無聲，比皇帝出來還要靜悄得多呢，連一根針跌在地下都聽得見響！

王小玉便啟朱脣，發皓齒，唱了幾句書兒。聲音初不甚大，只覺入耳有說不出來的妙境。五臟六腑裡，像熨斗熨過，無一處不伏貼。三萬六千個毛孔，像吃了人參果，無一個毛孔不暢快。唱了十數句之後，漸漸的越唱越高，忽然拔了一個尖兒，像一線鋼絲拋入天際，不禁暗暗叫絕。那知他於那極高的地方，尚能迴環轉折。幾囀之後，又高一層，接連有三四疊，節節高起。恍如由傲來峰西面攀登泰山的景象，初看傲來峰削壁千仞，以為上與天通。及至翻到傲來峰頂，才見扇子崖更在傲來峰上。及至翻到扇子崖，又見南天門更在扇子崖上。愈翻愈險，愈險愈奇。

那王小玉唱到極高的三四疊後，陡然一落，又極力騁其千迴百折的精神，如一條飛蛇在黃山三十六峰半中腰裡盤旋穿插。頃刻之間，周匝數遍。從此以後，愈唱愈低，愈低愈細，那聲音漸漸的就聽不見了。滿園子的人都屏氣凝神，不敢少動。約有兩三分鐘之久，彷彿有一點聲音從地底下發出。這一出之後，忽又揚起，像放那東洋煙火，一個彈子上天，隨化作千百道五色火光，縱橫散亂。這一聲飛起，即有無限聲音俱來並發。那彈弦子的亦全用輪指，忽大忽小，同他那聲音相和相合，有如花塢春曉，好鳥亂鳴。耳朵忙不過來，不曉得聽那一聲的為是。正在撩亂之際，忽聽霍然一聲，人弦俱寂。這時臺下叫好之聲，轟然雷動。

停了一會，鬧聲稍定，只聽那臺下正座上，有一個少年人，不到三十歲光景，是湖南口音，說道：「當年讀書，見古人形容歌聲的好處，有那『餘音繞梁，三日不絕』的話，我總不懂。空中設想，餘音怎樣會得繞梁呢？又怎會三日不絕呢？及至聽了小玉先生說書，才知古人措辭之妙。每次聽他說書之後，總有好幾天耳朵裡無非都是他的書，無論做什麼事，總不入神，反覺得『三日不絕』，這『三日』二字下得太少，還是孔子『三月不知肉味』，『三月』二字形容得透徹些！」旁邊人都說道：「夢湘先生論得透闢極了！『於我心有戚戚焉』！」

說著，那黑妞又上來說了一段，底下便又是白妞上場。這一段，聞旁邊人說，叫做「黑驢段」。聽了去，不過是一個士子見一個美人，騎了一個黑驢走過去的故事。將形容那美人，先形容那黑驢怎樣怎樣好法，待鋪敘到美人的好處，不過數語，這段書也就完了。其音節全是快板，越說越快。白香山詩云：「大珠小珠落玉盤。」可以盡之。其妙處在說得極快的時候，聽的人彷彿都趕不上聽，他卻字字清楚，無一字不送到人耳輪深處。這是他的獨到，然比著前一段卻未免遜一籌了。
…

《詩經》毛詩序

情發於聲，聲成文謂之音，治世之音安以樂，其政和；亂世之音怨以怒，其政乖；亡國之音哀以思，其民困。故正得失，動天地，感鬼神，莫近於詩。先王以是經夫婦，成孝敬，厚人倫，美教化，移風俗。

風聲雨聲讀書聲雖然都是『聲』，但不知有幾人能詮釋『地籟』之『樂』；或許『誦讀聲』偶然入耳，聽之卻有『弦外之音』。終於『寰宇的振動』一分為三，成為了『自然之聲』、『言語之音』以及『動人之樂』！王小玉說書，字字清晰詞詞明白，音似行雲且聲若流水，一時雷鳴九霄之外，忽而泉湧九地之下，彼音擬樂此聲知音，相追相逐鎔鑄成了『天籟』的聲樂旋律！！

───

事實上，那些文本

‧ 【Sonic π】聲波之傳播原理︰振動篇

‧ 【Sonic π】聲波之傳播原理︰原理篇《一》

‧ 【Sonic π】聲波之傳播原理︰共振篇《一》

‧ …

的點點滴滴，不只是進入 MEMS 的『先修課』，更為著在分殊專業的今天，所謂『普通科學』到底該如何講起又怎樣傳播，作點嘗試努力的吧！！

今天是『教師節』，省思現下『教』『學』關係的『實況』，不禁令人十分悵惘無奈的啊！！到底一切的教改使『學子』的『壓力』是增是減的呢？？

【為何壓力為零？？】

# sense_hat 原始碼
sense_hat/sense_hat.py 


    def get_pressure(self):
        """
        Returns the pressure in Millibars
        """

        self._init_pressure()  # Ensure pressure sensor is initialised

# 壓力為零是初始值！
        pressure = 0
        data = self._pressure.pressureRead()
# 或代表感測器讀取有誤耶？
        if (data[0]):  # Pressure valid
            pressure = data[1]
        return pressure

    @property
    def pressure(self):
        return self.get_pressure()

FreeSandal

勇闖新世界︰ W!o《卡夫卡村》變形祭︰感知自然‧尖端‧四

Key Features

輕。鬆。學。部落客

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