恒流源在高精度數(shù)字多用表中的設(shè)計與實現(xiàn)外文翻譯

1、附錄1英文參考資料The con sta nt curre nt source in high precisi on digital desig n and impleme ntatio n of multiple tablesThe constant current source in instrumentation, electronic equipment and high-tech scie nee and tech no logy is an importa nt comp onent of. In high precisi on digital multimeter, has th

2、e basic function of the resistance measurement, and the method of resistance measurement is usually through a resistance voltage (R-U) conv ersi on circuit, which adopts the method of con sta nt curre nt source.Precision constant current source resistance measurement accuracy depends largely on the

3、flow through the measured resista nce, whe n the con sta nt curre nt source with high accuracy, stable voltage measured resista nce, can improve the measureme nt accuracy of resista nce. Therefore, the desig n of a good stability, high accuracy of the constant current source is very important. Accor

4、ding to the actual needs, in the device select ion, con sideri ng the in flue nce of no ise, Wen Piao, desig n aeon sta nt curre nt source with good stability.1 con sta nt curre nt source is in troducedThe basic function of a constant current source is to eliminate or reduce the power supply voltage

5、,load resista nce and the in flue nce of en vir onmen tal temperature on the output current. The constant current source according to the adjustment of differe nt ways, can be divided into direct and in directadjustme nt of con sta nt curre nt source adjustable constant current source. Direct adjust

6、ing typeconstant current source circuit is simple, the main power supply and constant current devices, using the nonlinear characteristic of constant current devices are used to directly adjust the load current.For example, a constant current diode, but its current value is limited and stability is

7、poor. The in direct adjustme nt is a con sta nt curre nt circuit composed of electro nic tubes, tran sistors and other electro nic comp onents together constitute the. For example, feedback OP amplifier based onconstant current source, the use of such circuit can produce excellent performance consta

8、ntcurrent source.1.1 basic structure feedback con sta nt curre nt sourceFeedback constant current source through the negative feedback effect, to make comparis on betwee n the amplifier two in put voltage are equal, so as to mai nta in a constant output current. This circuit is connected in series w

9、ith the load change on the adjustment of the change of resistance to compensate theoutput current, so it is also called the series adjustable constant current source. Itmainly consists of a refere nce voltage source, a comparis on amplifier, adjust the sampli ng resista nee pipe, and other parts. Sp

10、ecific work process: through the sampli ng resistor to the output curre nt in to a voltage feedback amplifier in put, to compare, in comparis on with the refere nee voltage, the voltage error amplifier amplified to con trol the resista nee adjusti ng pipe to adjust the output curre nt, maintain con

11、sta nt output curre nt.1.2 basic circuit modelThere are many specific forms of feedback circuit of constant current source, accordi ng to the loadc onn ecti on mode of con sta nt curre nt source, divided into load grounding type and load of float in gtype, because of the con sta nt curre nt source i

12、s designed for the application of digital multiresistanee measurementfunction in the table, and the digital multimeter in measuring electric wirewhen the black pen and sheet resista nee digital multimeter internal circuit board is conn ected, so the measured load resista nee at one end is groun ded,

13、 so the desig n of the eon sta nt curre nt sourceshould be groun ded load type.2 eon sta nt curre nt source circuit desig nOn the basis of the design of high precision digital multi funetion meter measuri ng resistor, the resista nee profile of differe nt n eeds of differe nt eon sta nt curre nt sou

14、rce, and therefore n eed to desig n a 4 eon sta n curre nt output of the eon sta nt curre nt source circuit. Comb ined with the desig n of feedback eon sta nt curre nt source prin ciple, by differe nt sampli ng resista nee value, so as to achieve 4 differe nt eon sta nt curre nt source output.In the

15、 desig n of eon sta nt curre nt source, a refere nee voltage select ion is very important, it directly affects the stability of the constant current source. The referenee voltage requirements of high precision, small temperature drift, need to choose the referenee voltage chip with low noiseBased on

16、 the above requireme nts, eon sideri ng the choice of Lin ear Tech no logy Corporation shunt voltage referenee chip LM399, typical output voltage referenee value 6.95V. It has the following characteristics: drift coefficient, 0.5ppm/ C; dyn amic resista nee is small, the maximum of 1 ohm ;no ise vol

17、tage effective value of maximum 20 V in itial accuracy of 2%.LM399 internal thermostatic heater, can improve the effect of temperature drift, stable performanee for a long time. The constant current source circuit in the amplifier offset voltage, temperature drift ,no ise voltage will affect the acc

18、uracy of the eon sta nt curre nt source, so the error amplifier should have high in put impeda nee, low no ise and low leakage curre nt. Based on the above eon siderati on s,the desig n uses the ADI compa ny AD706, two operati onal amplifiers with intern al. It is a bipolar field effect tran sistor

19、(BiFET) of the in put stage, so it has high in put impeda nee, low in put bias current,low offset voltage, low offset voltage drift, low power consumption etc.Select the JFET to replace the tran sistor regulator, voltage con trolled eleme nt is JFET. A transistor is a current control device, it will

20、 introduce the base current to constant current source output, in a small constant current source output error, gate level JFET no current flows, so the effect ofconstant current source than the tran sistor effect of small, con sta nt curre nt source can obta in small error.The whole circuit design

21、can have 4 different constant current source output curre nt, output curre ntsampli ng resistor switchi ng con sta nt curre nt source by choos ing different. The circuit is divided into two parts, the first part is composed of LM399, U201A, JFET and Q201. The amplifier constant current receiver; the

22、 seco nd part is JFET Q202, Op U201B(R5,R6,sampli ng resista nce,R7,R8)aco nsta nt curre nt output curre nt source circuit.In summary, in view of the high precisi on digital versatile resista nee measurement function in the table, the design of the constant current source with high stability. Throug

23、h the an alysis of a typicalc on sta nt curre nt source circuit structure and working principle, some key factors which have impact on the accuracy of the constant current source, puts forward the design scheme of the constant current source, the scheme adopts the feedback circuit composed of operat

24、i onal amplifier with low noise to the design, the hardware principle diagram and give con crete. The experime ntal results show that: the desig n of the con sta nt curre nt source can meet the high precision digital multimeterresistanee measurement function application. The circuit has small volume

25、 and high reliability,flexible design, has a good value.附錄2譯文恒流源在高精度數(shù)字多用表中的設(shè)計與實現(xiàn)恒流源在儀器儀表、電子設(shè)備及高新科學(xué)技術(shù)中屬于一個重要的部件。在 高精度的數(shù)字多用表中，具有基本的電阻測量功能，而電阻測量的方法通常是經(jīng) 過電阻一電壓（R-U）轉(zhuǎn)換電路，即采用恒流源的方法。電阻的測量精度很大程度上取決于流過該被測電阻的恒流源電流的精度，當(dāng)恒流源電流精度高時，測得電阻的電壓穩(wěn)定，能夠提高電阻的測量精度。因此,設(shè)計一個穩(wěn)定性好、 準(zhǔn)確度高的恒流源是十分關(guān)鍵。本文根據(jù)實際的需要，在 器件選型上，考慮到噪聲、溫漂的影響，設(shè)計出

26、穩(wěn)定性好的恒流源。1恒流源介紹恒流源的基本作用是消除或消弱電源電壓、負(fù)載電阻和環(huán)境溫度變化對輸出電流的影響。恒流源按照調(diào)整方式的不同，可以分為直接調(diào)整型恒流源和間接調(diào) 整型恒流源。直接調(diào)整型恒流源電路簡單，主要有供電電源和恒流器件構(gòu)成，利 用了恒流器件的非線性特性對負(fù)載電流進(jìn)行直接的調(diào)整。例如恒流二極管，但其電流值有限且穩(wěn)定度也較差。間接調(diào)整型是由電子管、晶體管和其他電子元件一起構(gòu)成的恒流電路。例如基于0P放大器的反饋型恒流源，利用此類電路可以 制作出性能優(yōu)良的恒流源。1.1反饋型恒流源基本結(jié)構(gòu)反饋型恒流源是通過負(fù)反饋的作用，使加到比較放大器的兩個輸入端電壓相 等，從而保持輸出電流恒定。這種電

27、路是依靠與負(fù)載串聯(lián)的調(diào)整管的內(nèi)阻變化來補(bǔ)償輸出電流的變化，故又稱為串聯(lián)調(diào)整型恒流源。它主要由基準(zhǔn)電壓源、比 較放大器、調(diào)整管、采樣電阻等部分構(gòu)成。具體的工作過程：通過采樣電阻把輸 出電流轉(zhuǎn)變成電壓，反饋給比較放大器輸入端，在與基準(zhǔn)電壓相比較，放大器把 誤差電壓放大后去控制調(diào)整管的內(nèi)阻對輸出電流進(jìn)行調(diào)整，維持輸出電流恒定。1.2基本電路模型反饋型恒流源的具體電路形式有很多，根據(jù)恒流源的負(fù)載連接方式不同，分 為負(fù)載接地型和負(fù)載浮制型，由于所設(shè)計的恒流源是針對數(shù)字多用表中的電阻測 量功能的應(yīng)用，而數(shù)字多用表在測量電阻時其中黑表筆端與數(shù)字多用表內(nèi)部電路 板的地線相連，因而所測負(fù)載電阻有一端是接地的，

28、故所設(shè)計的恒流源應(yīng)是負(fù)載 接地型的。2恒流源電路設(shè)計依據(jù)所設(shè)計的高精度數(shù)字多用表的電阻測量功能，不同的電阻檔需要不同的恒流源電流，因而需設(shè)計一個有4種恒定電流輸出的恒流源電路。設(shè)計結(jié)合反饋型恒流源基本工作原理，通過選擇不同的采樣電阻值，從而達(dá)到4路不同的恒流 源電流輸出。在恒流源的設(shè)計中，基準(zhǔn)電壓的選擇十分重要，它直接影響著恒流源的穩(wěn)定 性能?；鶞?zhǔn)電壓要求精度高，溫漂影響小，需要選擇低噪聲的基準(zhǔn)電壓芯片?；谝陨系囊?，綜合考慮后選擇了凌特公司的并聯(lián)電壓參考芯片 LM399, 輸出基準(zhǔn)電壓的典型值為6.95V。它具有以下特點：溫漂系數(shù)小，0.5ppm/ C； 動態(tài)電阻小，最大1 Q;噪聲電壓有

29、效值最大20卩V;初始精度2%LM399內(nèi)部自帶恒溫加熱器，能夠改善溫度漂移帶來的影響，長期的穩(wěn)定性 能好。其恒流源電路中的運放的失調(diào)電壓、溫漂、噪聲電壓等會影響恒流源電流的精度，因此誤差比較放大器應(yīng)該具有高輸入阻抗、低噪聲和超低漏電流。基于以上考慮，設(shè)計采用 ADI公司的AD706,內(nèi)部含有兩個運算放大器。它是 具有雙極性場效應(yīng)晶體管(BiFET)的輸入級，因此具有高的輸入阻抗、低輸入偏置電流，低失調(diào)電壓，低失調(diào)電壓溫漂，低功耗等特點。調(diào)整管選擇JFET替代了晶體管，JFET是壓控型元件。晶體管是電流控制 型器件，它的基極電流會引入到恒流源電流輸出端，在小電流恒流源輸出時誤差影響大，JFET

30、的柵級沒有電流流入，故對恒流源電流的影響遠(yuǎn)比晶體管的影響 小，可以獲得誤差極小的恒流源。所設(shè)計的整體電路可以有4路不同的恒流源電流輸出，通過選擇不同的采樣 電阻來切換恒流源的輸出電流。電路分兩部分，第一部分由LM399、運放U201A、 JFET Q201等構(gòu)成恒流接收器；第二部分有運放 U201B JFET Q202、采樣電 阻(R5,R6,R7,R8)等構(gòu)成恒流源電流輸出電路。綜上所述，針對高精度數(shù)字多用表中的電阻測量功能，設(shè)計了一種高穩(wěn)定度 的恒流源。通過分析典型的恒流源的電路結(jié)構(gòu)和工作原理，研究了影響恒流源精度的一些關(guān)鍵因素，提出了恒流源的設(shè)計方案，該方案采用由低噪聲的運算放大 器構(gòu)成

31、的反饋型電路來設(shè)計，給出了具體的硬件原理圖。實驗結(jié)果表明：設(shè)計的 恒流源能夠滿足高精度的數(shù)字多用表中電阻測量功能應(yīng)用。該電路具有較小的體積和高可靠性，設(shè)計方式靈活，具有很好的使用價值。目錄錯誤！未定義書簽錯誤！未定義書簽1 總論1.1項目概況1.2建設(shè)單位概況錯誤！未定義書簽1.3項目提出的理由與過程 錯誤！未定義書簽1.4可行性研究報告編制依據(jù)錯誤！未定義書簽1.5可行性研究報告編制原則錯誤！未定義書簽1.6可行性研究范圍 錯誤！未定義書簽1.7結(jié)論與建議 錯誤！未定義書簽2項目建設(shè)背景和必要性 錯誤！未定義書簽2.1項目區(qū)基本狀況 錯誤！未定義書簽2.2項目背景 錯誤！未定義書簽2.3項目建設(shè)的必要性 錯誤！未定義書簽3市場分析 錯誤！未定義書簽3.1物流園區(qū)的發(fā)展概況 錯誤！未定義書簽3.2市場供求現(xiàn)狀 錯誤！未定義書簽3.3目標(biāo)市場定位 錯誤！未定義書簽3.4市場競爭力分析 錯誤！未定義書簽4項目選址和建設(shè)條件 錯誤！未定義書簽4.1選址原則 錯誤！未定義書簽4.2項目選址 錯誤！未定義書簽4.3場址所在位置現(xiàn)狀 錯誤！未定義書簽4.4建設(shè)條件 錯誤！未定義書簽5主要功能和建設(shè)規(guī)模 錯誤！未定義書簽5.1主要功能 錯誤！未定義書簽5.2建設(shè)規(guī)模及內(nèi)容 錯誤！未定義書簽6工程建設(shè)方案 錯誤！未定義書簽6.1設(shè)計依據(jù) 錯誤！