【正文】 a RS232 interface, this interface can achieve point to point munication, but this approach can not be achieved networking. RS485 then appears to solve this problem.RS232, RS422 and RS485 serial data interface is standard, initially by the Electronic Industries Association (EIA) developed and published, RS232 released in 1962, named for EIA232E, As industry standards to ensure patibility between products from different manufacturers. RS422 evolved from the RS232, which is to pensate for the lack of RS232 raised. RS232 munications to improve the short distance, low rate of defects, RS422 munication interface defines a balance, transfer rate up to 10Mb / s, the transmission distance was extended to 4000 feet (rates of less than 100kb / s time), and allows a balance on the bus up to 10 receivers. RS422 is a single transmission, multimachine receives a oneway, balanced transmission standard, was named TIA/EIA422A standards. To expand the application range, EIA again in 1983 on the basis of the RS422 RS485 standard developed to increase the multipoint, twoway munications capability that allows multiple transmitters connected to the same bus, while increasing the transmitter drive capability and conflict protection features, the expansion of the bus mon mode range, named after TIA/EIA485A standards. Since EIA standards are based on remendations made by RS as a prefix, so in the munications industry, are still accustomed to the above criteria to RS prefix title.The analog signal is converted to digital signal circuits known analog / digital conversion circuit (or A / D conversion circuit), an analog signal into a digital signal to go through the sample and hold, quantization, coding 4 process. There is now a monolithic integrated circuit to plete the A / D conversion function, this analog / digital conversion circuit is often referred to as analog / digital converter. According to analog, digital converter conversion works differently, analog / digital converter can be divided into successive parison mold / digital converters, mold double integral A / D converter and so are several.Double integral type A / D converter39。s 89C51 is an efficient microcontroller. 89C MCU as many embedded control system provides a high flexibility and lowcost price. In this design, the calculation is simple, flexible circuit, this singlechip fully meet the design requirements, but also makes the design more simple and convenient. 基于此，本文主要設(shè)計(jì)一個(gè)基于MSC51單片機(jī)控制的交流電參數(shù)測(cè)量?jī)x，此儀器可以測(cè)量交流電參數(shù)的電壓，功率。該儀器可以廣泛適用于電力系統(tǒng)及相關(guān)行業(yè)繼電保護(hù)和計(jì)量專(zhuān)業(yè)、工礦企業(yè)、石油化工、冶金企業(yè)的二次回路檢查。雙積分型A/D轉(zhuǎn)換器的轉(zhuǎn)換精度主要取決于位數(shù)、運(yùn)算放大器和比較器的靈敏度和零點(diǎn)漂移等因素的影響。雙積分型A/D轉(zhuǎn)換器的最大優(yōu)點(diǎn)是工作穩(wěn)定，抗干擾能力強(qiáng)。現(xiàn)在已存在單片集成電路能夠完成模／數(shù)轉(zhuǎn)換的功能，這種模／數(shù)轉(zhuǎn)換的集成電路通常被稱(chēng)作模／數(shù)轉(zhuǎn)換器。由于EIA提出的建議標(biāo)準(zhǔn)都是以“RS”作為前綴，所以在通訊工業(yè)領(lǐng)域，仍然習(xí)慣將上述標(biāo)準(zhǔn)以RS作前綴稱(chēng)謂。RS422是一種單機(jī)發(fā)送、多機(jī)接收的單向、平衡傳輸規(guī)范，被命名為T(mén)IA/EIA422A標(biāo)準(zhǔn)。RS422由RS232發(fā)展而來(lái)，它是為彌補(bǔ)RS232之不足而提出的。隨后出現(xiàn)的RS485解決了這個(gè)問(wèn)題的方案。究其原因就是企業(yè)信息化的需要，企業(yè)在儀表選型時(shí)其中的一個(gè)必要條件就是要具有聯(lián)網(wǎng)通信接口。在本設(shè)計(jì)中，由于計(jì)算較為簡(jiǎn)單，電路靈活，這款單片機(jī)完全符合設(shè)計(jì)的要求，同時(shí)也使得設(shè)計(jì)更加的簡(jiǎn)單方便。由于將多功能8位CPU和閃爍存儲(chǔ)器組合在單個(gè)芯片中，ATMEL的89C51是一種高效微控制器。 本設(shè)計(jì)中所用的89C51單片機(jī)是一種帶4K字節(jié)閃爍可編程可擦除只讀存儲(chǔ)器的低電壓、高性能CMOS8位微處理器。具有線(xiàn)路相對(duì)簡(jiǎn)單，結(jié)構(gòu)緊湊，價(jià)格低廉，頻率穩(wěn)定度高，抗干擾能力強(qiáng)，用途廣泛等優(yōu)點(diǎn)，并且能夠?qū)Σㄐ芜M(jìn)行細(xì)微調(diào)整，改良波形，使其滿(mǎn)足系統(tǒng)的要求。華北科技學(xué)院畢業(yè)設(shè)計(jì)（論文）基于單片機(jī)原理的多功能測(cè)量?jī)x的設(shè)計(jì)畢業(yè)設(shè)計(jì)目錄設(shè)計(jì)總說(shuō)明 IVGeneral Design Description VI一 .緒論 9 9 9 51單片機(jī)簡(jiǎn)介 10 1電壓有效值的測(cè)量 12 13 單相有功功率、無(wú)功功率、視在功率的測(cè)量 14 三相有功功率的測(cè)量 15 15 16 使用功能要求 17 儀器設(shè)計(jì)的總體框架和各模塊的劃分 17四． 硬件電路設(shè)計(jì) 19 19 電壓信號(hào)采集電路 19 電流信號(hào)采集電路 20 21 A/D轉(zhuǎn)換電路 22 74ls138譯碼器 32 A/D轉(zhuǎn)換電路 34 35 35 37 37 39 CD4511 40 40 41 41 41 42 通信接口電路 44 Rs485特點(diǎn) 44 44 rs485功能 45 RS485通信電路 46五．系統(tǒng)軟件設(shè)計(jì) 47 程序模塊的劃分 47 結(jié)構(gòu)化程序的設(shè)計(jì)方法 47 軟件模塊 48 主程序流程圖 48 50 50 A/D轉(zhuǎn)換程序 52 53 RS485 53六．總結(jié)與展望 55附錄A: 總電路圖 58附錄B: 總的系統(tǒng)框圖 59附錄C: 程序 60致 謝 64基于單片機(jī)原理的多功能測(cè)量?jī)x的設(shè)計(jì)設(shè)計(jì)總說(shuō)明隨著電力系統(tǒng)的快速發(fā)展，電網(wǎng)容量不斷增大，結(jié)構(gòu)日趨復(fù)雜，電力系統(tǒng)中實(shí)時(shí)監(jiān)控、調(diào)度的自動(dòng)化顯得尤為重要，而電力參數(shù)的數(shù)據(jù)采集又是實(shí)現(xiàn)自動(dòng)化的重要環(huán)節(jié)，如何快速準(zhǔn)確地采集系統(tǒng)中各元件的電參數(shù)（電壓、電流、功率、功率因數(shù)等）是實(shí)現(xiàn)電力系統(tǒng)自動(dòng)化的一個(gè)重要因素。 利用單片機(jī)采用程序設(shè)計(jì)方法來(lái)產(chǎn)生低頻信號(hào)，其頻率底線(xiàn)很低。只要對(duì)電路稍加修改，調(diào)整程序，即可完成功能升級(jí)。這款單片機(jī)的可擦除只讀存儲(chǔ)器可以反復(fù)擦除100次，采用ATMEL高密度非易失存儲(chǔ)器制造技術(shù)制造，與工業(yè)標(biāo)準(zhǔn)的MCS51指令集和輸出管腳相兼容。89C單片機(jī)為很多嵌入式控制系統(tǒng)提供了一種靈活性高且價(jià)廉價(jià)。 智能儀表是隨著80年代初單片機(jī)技術(shù)的成熟而發(fā)展起來(lái)的，現(xiàn)在世界儀表市場(chǎng)基本被智能儀表所壟斷。最初是數(shù)據(jù)模擬信號(hào)輸出簡(jiǎn)單過(guò)程量，后來(lái)儀表接口是RS232接口，這種接口可以實(shí)現(xiàn)點(diǎn)對(duì)點(diǎn)的通信方式，但這種方式不能實(shí)現(xiàn)聯(lián)網(wǎng)功能。RS23RS422與RS485都是串行數(shù)據(jù)接口標(biāo)準(zhǔn)，最初都是由電子工業(yè)協(xié)會(huì)（EIA）制訂并發(fā)布的，RS232在1962年發(fā)布，命名為EIA232E，作為工業(yè)標(biāo)準(zhǔn)，以保證不同廠(chǎng)家產(chǎn)品之間的兼容。為改進(jìn)RS232通信距離短、速率低的缺點(diǎn)，RS422定義了一種平衡通信接口，將傳輸速率提高到10Mb/s，傳輸距離延長(zhǎng)到4000英尺（速率低于100kb/s時(shí)），并允許在一條平衡總線(xiàn)上連接最多10個(gè)接收器。為擴(kuò)展應(yīng)用范圍，EIA又于1983年在RS422基礎(chǔ)上制定了RS485標(biāo)準(zhǔn)，增加了多點(diǎn)、雙向通信能力，即允許多個(gè)發(fā)送器連接到同一條總線(xiàn)上，同時(shí)增加了發(fā)送器的驅(qū)動(dòng)能力和沖突保護(hù)特性，擴(kuò)展了總線(xiàn)共模范圍，后命名為T(mén)IA/EIA485A標(biāo)準(zhǔn)。將模擬信號(hào)轉(zhuǎn)換為數(shù)字信號(hào)的電路稱(chēng)作模／數(shù)轉(zhuǎn)換電路(或A／D轉(zhuǎn)換電路)，模擬信號(hào)轉(zhuǎn)換成數(shù)字信號(hào)要經(jīng)歷采樣、保持、量化、編碼4個(gè)過(guò)程。根據(jù)模，數(shù)轉(zhuǎn)換器的轉(zhuǎn)換原理不同，模／數(shù)轉(zhuǎn)換器可分為逐次比較型模／數(shù)轉(zhuǎn)換器、雙積分型模／數(shù)轉(zhuǎn)換器等幾種。雙積分型A/D轉(zhuǎn)換器的數(shù)字輸出與積分電阻R、積分電容C、時(shí)鐘頻率fcp無(wú)關(guān)，最大缺點(diǎn)是速度較慢，所以主要用于數(shù)字電壓表等低速測(cè)試系統(tǒng)中。電能測(cè)量?jī)x將多個(gè)電能參數(shù)形成一體化儀表后，只攜帶一個(gè)儀表就能完成電壓、電流、相位、功率、功率因數(shù)等多種功能真正做到全面準(zhǔn)確地反映用電系統(tǒng)的電能質(zhì)量。它的出現(xiàn)簡(jiǎn)化了操作員的工作，同時(shí)也帶來(lái)相當(dāng)?shù)慕?jīng)濟(jì)和社會(huì)效益。關(guān)鍵詞：數(shù)字信號(hào)處理器；數(shù)據(jù)采集；RS485；A/D轉(zhuǎn)換Based on the principle of multichip design measuring instrumentGeneral Design DescriptionWith the rapid development of the power system, power grid capacity is increasing, the structure more plex, realtime power system monitoring, scheduling automation is particularly important, and electrical parameters of the automated data acquisition is an important part of how to quickly and accurately capture system electrical parameters of each ponent (voltage, current, power, power factor, etc.) is to achieve power system automation is an important factor.Using microcontroller programming method used to generate a low frequency signal whose frequency is the bottom line low. Has a relatively simple circuit, pact, inexpensive, high frequency stability, antiinterference ability, versatility, etc., and can finetune the waveform, improved waveform to meet the system requirements. As long as the circuit slightly modified to adjust the program to plete the feature upgrades.Used in this design is an 89C51 microcontroller with 4K bytes of flash erasable programmable readonly memory, low voltage, high perfor