【機(jī)械類畢業(yè)論文中英文對(duì)照文獻(xiàn)翻譯】壓力傳感器
【機(jī)械類畢業(yè)論文中英文對(duì)照文獻(xiàn)翻譯】壓力傳感器,機(jī)械類畢業(yè)論文中英文對(duì)照文獻(xiàn)翻譯,機(jī)械類,畢業(yè)論文,中英文,對(duì)照,對(duì)比,比照,文獻(xiàn),翻譯,壓力傳感器
附 錄
Pressure sensors papers
Reasonable pressure sensor error compensation is the key to its application. Pressure sensors are mainly offset error, sensitivity error, linear error and lag errors, the paper will introduce the four errors on the mechanism and the effects of the test results, will be presented at the same time to improve the measurement accuracy of pressure calibration method and application examples .
Currently on the market a variety of sensor types, which allows design engineers can choose the pressure sensor system. These sensors not only include the most basic converter, but also more complex circuits with on-chip, highly integrated sensor. Because of these differences, the design engineer must be enough as far as possible compensation of pressure sensor measurement error, which is to ensure that the design and application of sensors to meet the requirements of an important step. In some cases, compensation can increase the sensor in the application of the overall performance.
Based on Motorola's pressure sensor as an example, the application of the concept involved in the design of a variety of pressure sensor applications.
Motorola mainstream production pressure piezoresistive sensor is a monolithic device, the device has 3 categories:
1. Basic calibration or without compensation;
2. There are calibration and temperature compensation;
3. There are calibration, compensation and amplification.
Offset, the scope of calibration and temperature compensation can be through the thin film resistor networks, the thin film resistor networks in the process of laser package amendments.
The sensor is usually used in conjunction with the micro-controller, and microcontroller embedded software itself, established a mathematical model of the sensor. Microcontroller reads the output voltage through the ADC conversion, the model can be converted to the pressure of the volume of voltage measurements.
The simplest sensor is the transfer function of the mathematical model. The model calibration over the entire optimization process and maturity model will be marked with the fixed-point increase.
From the point of view of metrology, measurement error has a very strict definition: it is characterized by measurement of pressure and the difference between the actual pressure. Usually can not directly be the actual pressure, but through the use of appropriate criteria to estimate the pressure, the measurement accuracy are usually more than those measured using equipment at least 10 times higher than the instrument as a measurement standard.
Without calibration of the system as a result can only use the typical value of sensitivity and offset the output voltage is converted to pressure, the pressure measured will have a margin of error as shown in Figure 1.
This initial error without calibration by the following components:
a. offset error. As the pressure in the entire range of vertical shift to maintain a constant, so the proliferation and laser conditioning converter changes the amendment would have offset error.
b. The sensitivity of error, resulting in errors in direct proportion to the size and pressure. If the device is higher than the typical value of the sensitivity, the sensitivity of the error will be incremental pressure function (see Figure 1). If the sensitivity is lower than the typical value, then the sensitivity of the error will be decreasing function of pressure. The cause of the error diffusion process is to change.
c. Linearity Error. This is an initial error factor less affected, the error is the cause of the physical non-linear silicon, but with the sensor amplifier, should also include non-linear amplifier. Linear error curve can be concave curve, it could be a convex curve.
d. Lag Error: In most cases, the lag error can be ignored completely, because silicon has a higher degree of mechanical stiffness. Changes in general just a lot of pressure to consider the case of hysteresis error.
Calibration can eliminate or greatly reduce these errors, and compensation technique is usually required to identify the parameters of the actual transfer function, rather than simply the use of typical values. Potentiometer, adjustable resistance, and other hardware can be used in the compensation process, while the software is able to achieve more flexibility in the work of this error compensation.
Calibration method that can eliminate the transfer function against the Agency to compensate the offset drift error, such as the auto-zero calibration method.
Offset zero calibration is usually carried out under pressure, especially in the differential sensor, because under the conditions of the nominal differential pressure is usually 0. For pure sensor offset calibration will be difficult, because it either needs to read a pressure system to measure the atmospheric pressure in the environment under the conditions of the calibration of pressure or need to obtain the pressure of expectations of the pressure controller.
Zero differential pressure sensor is very accurate calibration, because the pressure of strict demarcation is 0. On the other hand, the pressure of 0:00 is not the accuracy of the calibration depends on the pressure controller or the performance measurement system.
Choice of calibration pressure
Calibration is very important selection pressure, which determines the accuracy to obtain the best pressure range. In fact, after calibration offset actual standard fixed-point error in the Department and has been to maintain a smaller minimum value. Therefore, the reference points must be in accordance with the scope of the target selection pressure, and pressure range can not be consistent with the scope of work.
In order to convert the pressure of the output voltage value, usually as a result of the actual sensitivity is unknown, and therefore the mathematical model used for a typical single-point calibration sensitivity.
Said that the red curve calibration offset (PCAL = 0) after the error curve, the error can be found that calibration curve relative to the black before the error had a vertical offset curve.
This calibration method and calibration method that is more stringent requirements to achieve a higher cost. However, compared with the calibration point, the method can significantly improve the accuracy of the system, because the method is not only an offset calibration, the calibration of the sensor sensitivity. Therefore, the calculation error can be used in the actual value of sensitivity, and the atypical values.
That improve the accuracy of the green curve. Here, calibration is trillion 0-500 bar (full scale) conditions. As the marked point on the error close to 0, so the pressure of expectations to be the smallest range of measurement error, the correct set of these points, it is particularly important.
Some applications require the pressure in the whole range of high accuracy. In these applications, can be used multi-point calibration method to get the best results. In multi-point calibration method, not only considered the error of offset and sensitivity, but also takes into account most of the linear error curve shown in purple. The mathematical model used here, with each calibration interval (between the two reference points) exactly the same as a two-tier calibration.
Three-point calibration
As mentioned earlier, the linear form of a consistent error and the error curve in line with the quadratic equation of the curve, with a predictable size and shape. Did not use the amplifier for the sensor, especially because of the nonlinear sensor is based on the nature of mechanical reasons (this is caused by the pressure of silicon thin-film).
Linear description of the error characteristics of a typical example can be calculated the average linear error to determine the polynomial function (a × 2 + bx + c) be the parameter. Determine the a, b and c of the model after the same type of sensor is valid. This method can be no fixed points marked the first three cases of linear error compensation effectively.
Examples of compensation MPX2300 Motorola, MPX2300 is a blood pressure measurement is mainly used in the temperature compensation sensor. Polynomial model can be an average of 10 sensors to be linear error compensation of the error after the initial maximum linearity error of about ten to one-twentieth, as shown in dotted line in Figure 3.
The error compensation method can be only two points calibration for high-performance low-cost sensors to improve the device (full scale error of less than 0.05%).
Of course, design engineers practical application in accordance with the accuracy requirements, choosing the most appropriate calibration method, in addition to the need to consider system cost. As a result of a variety of integration options and compensation technology, design engineers can design requirements according to different methods of selecting appropriate.
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壓力傳感器
合理進(jìn)行壓力傳感器的誤差補(bǔ)償是其應(yīng)用的關(guān)鍵。壓力傳感器主要有偏移量誤差、靈敏度誤差、線性誤差和滯后誤差，本文將介紹這四種誤差產(chǎn)生的機(jī)理和對(duì)測試結(jié)果的影響，同時(shí)將介紹為提高測量精度的壓力標(biāo)定方法以及應(yīng)用實(shí)例。
目前市場上傳感器種類豐富多樣，這使得設(shè)計(jì)工程師可以選擇系統(tǒng)所需的壓力傳感器。這些傳感器既包括最基本的變換器，也包括更為復(fù)雜的帶有片上電路的高集成度傳感器。由于存在這些差異，設(shè)計(jì)工程師必須盡可能夠補(bǔ)償壓力傳感器的測量誤差，這是保證傳感器滿足設(shè)計(jì)和應(yīng)用要求的重要步驟。在某些情況下，補(bǔ)償還能提高傳感器在應(yīng)用中的整體性能。
本文以摩托羅拉公司的壓力傳感器為例，所涉及的概念適用于各種壓力傳感器的設(shè)計(jì)應(yīng)用。
摩托羅拉公司生產(chǎn)的主流壓力傳感器是一種單片壓阻器件，該器件具有3類：
1. 基本的或未加補(bǔ)償標(biāo)定；
2. 有標(biāo)定并進(jìn)行溫度補(bǔ)償；
3. 有標(biāo)定、補(bǔ)償和放大。
偏移量、范圍標(biāo)定以及溫度補(bǔ)償均可以通過薄膜電阻網(wǎng)絡(luò)實(shí)現(xiàn)，這種薄膜電阻網(wǎng)絡(luò)在封裝過程中采用激光修正。
該傳感器通常與微控制器結(jié)合使用，而微控制器的嵌入軟件本身建立了傳感器數(shù)學(xué)模型。微控制器讀取了輸出電壓后，通過模數(shù)轉(zhuǎn)換器的變換，該模型可以將電壓量轉(zhuǎn)換為壓力測量值。 傳感器最簡單的數(shù)學(xué)模型即為傳遞函數(shù)。該模型可在整個(gè)標(biāo)定過程中進(jìn)行優(yōu)化，并且模型的成熟度將隨標(biāo)定點(diǎn)的增加而增加。
從計(jì)量學(xué)的角度看，測量誤差具有相當(dāng)嚴(yán)格的定義：它表征了測量壓力與實(shí)際壓力之間的差異。而通常無法直接得到實(shí)際壓力，但可以通過采用適當(dāng)?shù)膲毫?biāo)準(zhǔn)加以估計(jì)，計(jì)量人員通常采用那些精度比被測設(shè)備高出至少10倍的儀器作為測量標(biāo)準(zhǔn)。
由于未經(jīng)標(biāo)定的系統(tǒng)只能使用典型的靈敏度和偏移值將輸出電壓轉(zhuǎn)換為壓力，測得的壓力將產(chǎn)生如圖1所示的誤差。
這種未經(jīng)標(biāo)定的初始誤差由以下幾個(gè)部分組成：
a. 偏移量誤差。由于在整個(gè)壓力范圍內(nèi)垂直偏移保持恒定，因此變換器擴(kuò)散和激光調(diào)節(jié)修正的變化將產(chǎn)生偏移量誤差。
b. 靈敏度誤差，產(chǎn)生誤差大小與壓力成正比。如果設(shè)備的靈敏度高于典型值，靈敏度誤差將是壓力的遞增函數(shù)（見圖1）。如果靈敏度低于典型值，那么靈敏度誤差將是壓力的遞減函數(shù)。該誤差的產(chǎn)生原因在于擴(kuò)散過程的變化。
c. 線性誤差。這是一個(gè)對(duì)初始誤差影響較小的因素，該誤差的產(chǎn)生原因在于硅片的物理非線性，但對(duì)于帶放大器的傳感器，還應(yīng)包括放大器的非線性。線性誤差曲線可以是凹形曲線，也可以是凸形曲線。
d. 滯后誤差：在大多數(shù)情形中，滯后誤差完全可以忽略不計(jì)，因?yàn)楣杵哂泻芨叩臋C(jī)械剛度。一般只需在壓力變化很大的情形中考慮滯后誤差。
標(biāo)定可消除或極大地減小這些誤差，而補(bǔ)償技術(shù)通常要求確定系統(tǒng)實(shí)際傳遞函數(shù)的參數(shù)，而不是簡單的使用典型值。電位計(jì)、可調(diào)電阻以及其他硬件均可在補(bǔ)償過程中采用，而軟件則能更靈活地實(shí)現(xiàn)這種誤差補(bǔ)償工作。一點(diǎn)標(biāo)定法可通過消除傳遞函數(shù)零點(diǎn)處的漂移來補(bǔ)償偏移量誤差，這類標(biāo)定方法稱為自動(dòng)歸零。
偏移量標(biāo)定通常在零壓力下進(jìn)行，特別是在差動(dòng)傳感器中，因?yàn)樵跇?biāo)稱條件下差動(dòng)壓力通常為0。對(duì)于純傳感器，偏移量標(biāo)定則要困難一些，因?yàn)樗葱枰粋€(gè)壓力讀取系統(tǒng)，用以測量其在環(huán)境大氣壓力條件下的標(biāo)定壓力值，要么需要獲取期望壓力的壓力控制器。
差動(dòng)傳感器的零壓力標(biāo)定非常精確，因?yàn)闃?biāo)定壓力嚴(yán)格為0。另一方面，壓力不為0時(shí)的標(biāo)定精確度取決于壓力控制器或測量系統(tǒng)的性能。選擇標(biāo)定壓力，標(biāo)定壓力的選取非常重要，因其決定了獲取最佳精度的壓力范圍。實(shí)際上，經(jīng)過標(biāo)定后實(shí)際的偏移量誤差在標(biāo)定點(diǎn)處最小并一直保持較小的值。因此，標(biāo)定點(diǎn)必須根據(jù)目標(biāo)壓力范圍加以選擇，而壓力范圍可以不與工作范圍相一致。
為了將輸出電壓轉(zhuǎn)換為壓力值，由于實(shí)際的靈敏度往往是未知，因此在數(shù)學(xué)模型中通常采用典型靈敏度進(jìn)行單點(diǎn)標(biāo)定。紅色曲線表示進(jìn)行偏移量標(biāo)定（PCAL=0）后的誤差曲線，可以發(fā)現(xiàn)誤差曲線相對(duì)于表示標(biāo)定前誤差的黑色曲線產(chǎn)生了垂直偏移。這種標(biāo)定方法與一點(diǎn)標(biāo)定法相比要求更為嚴(yán)格，實(shí)現(xiàn)成本也更高。然而與一點(diǎn)標(biāo)定法相比，該方法可顯著提高系統(tǒng)的精度，因?yàn)樵摲椒ú粌H標(biāo)定了偏移量，還標(biāo)定了傳感器的靈敏度。因此在誤差計(jì)算中可以使用靈敏度實(shí)際值，而非典型值。
綠色曲線表示精度提高。在這里，標(biāo)定是在0至500兆巴（滿標(biāo)度）條件下進(jìn)行。由于在標(biāo)定點(diǎn)上誤差接近于0，因此為了在期望的壓力范圍內(nèi)得到最小的測量誤差，正確地設(shè)定這些點(diǎn)就顯得尤為重要。某些應(yīng)用中要求在整個(gè)壓力范圍內(nèi)保持較高的精確度。在這些應(yīng)用中，可以采用多點(diǎn)標(biāo)定法來得到最理想的結(jié)果。在多點(diǎn)標(biāo)定法中，不僅考慮了偏移量和靈敏度誤差，還考慮了大部分的線性誤差，紫紅色曲線所示。這兒用的數(shù)學(xué)模型與每個(gè)標(biāo)定間距（在兩個(gè)標(biāo)定點(diǎn)之間）的兩級(jí)標(biāo)定完全一樣。
三點(diǎn)標(biāo)定 ，如前所述，線性誤差具有一致的形式，且誤差曲線符合二次方程的曲線，具有可預(yù)測的大小和形狀。對(duì)于未采用放大器的傳感器更是如此，因?yàn)閭鞲衅鞯姆蔷€性從本質(zhì)上是基于機(jī)械原因（這是由硅片的薄膜壓力引起）。
線性誤差特性的描述可以通過計(jì)算典型實(shí)例的平均線性誤差，確定多項(xiàng)式函數(shù)（a×2+bx+c）的參數(shù)而得到。確定了a、b和c后得到的模型對(duì)于相同類型的傳感器都是有效的。該方法能在無需第3個(gè)標(biāo)定點(diǎn)的情況下有效地補(bǔ)償線性誤差。
摩托羅拉MPX2300的補(bǔ)償實(shí)例，MPX2300是一種主要應(yīng)用于血壓測量的溫度補(bǔ)償傳感器。多項(xiàng)式模型可由10個(gè)傳感器的平均線性誤差得到，補(bǔ)償后的誤差約為最大初始線性誤差的十至二十分之一。該誤差補(bǔ)償方法只需兩點(diǎn)標(biāo)定即可將低成本傳感器改進(jìn)為高性能器件（誤差小于滿標(biāo)度的0.05%）。
當(dāng)然設(shè)計(jì)工程師要根據(jù)實(shí)際應(yīng)用的精確度要求，選擇最適合的標(biāo)定方法，此外還需要考慮系統(tǒng)成本。由于有多種集成度和補(bǔ)償技術(shù)可供選擇，設(shè)計(jì)工程師可根據(jù)不同的設(shè)計(jì)要求選擇適當(dāng)?shù)姆椒ā?
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