【正文】 波形W3)，送至雙向計數(shù)器 74LS193 的加脈沖輸入端 CU，進行加法計數(shù)；此時，下面與非門關閉，其輸出為高電平 (波形 W4)。一般只需要三條碼道，這里的碼道實際上已不具有絕對編碼器碼道的意義，而是產(chǎn)生計數(shù) 脈沖。通常，若編碼器有 N個（碼道）輸出信號，其相位差為 π/ N ，可計數(shù)脈沖為 2N 倍光柵數(shù)，現(xiàn)在 N=2。由圖 4 還可看出，在原一個脈沖信號的周期內(nèi)，得到了四個計數(shù)脈沖。 因光電檢測裝置安裝在生產(chǎn)現(xiàn)場，受生產(chǎn)現(xiàn) 場環(huán)境因素影響導致光電檢測裝置不能可靠的工作。 合理選擇光電檢測裝置輸出信號 傳輸介質(zhì)，采用雙絞屏蔽電纜取代普通屏蔽電纜。當引錠桿擋住光電裝置發(fā)射出的紅外光時，光電信號為 “0” ；當紅外光透過引錠桿中部 2 個小圓孔時，光電裝置發(fā)出信號 2和 3，均為 “1” 。結合光電檢測裝置在生產(chǎn)過程控制中的應用實踐，在控制系統(tǒng)設計中；不宜采用光電檢測裝置的信號作為重要的控制信號，以避免光電裝置突然損壞或工作不穩(wěn)定（環(huán)境高溫、濕度大、機械振動、外力碰創(chuàng)等）引起其它設備事故。 根據(jù)光檢測電 裝置的工作過程，只要現(xiàn)場測定送引錠過程中各個光電信號發(fā)生的時間，結合送引錠過程與光電信號的關系，利用 PLC 應用程序中的相關數(shù)據(jù)，編制符合要求的 PLC 程序，將 PLC 程序輸出信號輸入至 PLC 的輸入模塊，替代原光電信號的輸入信號。在連鑄生產(chǎn)的送引錠過程要求光電檢測裝置產(chǎn)生有時序性的電信號，同時，該信號與整個過程不同階段相對應。例如；光電檢測裝置安裝在生產(chǎn)設備本體，其信號經(jīng)電纜傳輸至控制系統(tǒng)的距離一般在 20— 100 米，傳輸電纜雖然一般都選用多芯屏蔽電纜，但由于電纜的 導線電阻及線間電容的影響再加上和其它電纜同在一起敷設，極易受到各種電磁干擾的影響，因此引起波形失真，從而使反饋到調(diào)速系統(tǒng)的信號與實際值的偏差，而導致系統(tǒng)精度下降。 16 應用中問題分析及改進措施 應用中問題分析 光電檢測裝置的發(fā)射和接收裝置都安裝在生產(chǎn)現(xiàn)場，在使用中暴露出許多缺陷，其有內(nèi)在因素也有外在因素，主要表現(xiàn)在以下幾個方面： 發(fā)射裝置或接受裝置因機械震動等原因而引起的移位或偏移，導致接收裝置不能可靠的接收到光信號，而不能產(chǎn)生電信號。在這里，采用了 有記憶功能 的 D 型觸發(fā)器和時鐘發(fā)生電路。從 A， B兩個輸出信號的相位關系（超前或滯后）可判斷旋轉(zhuǎn)的方向。 實際使用時，方向盤頻繁地進行順時針和逆時針轉(zhuǎn)動，由于存在量化誤差，工作較長一段時間后，方向盤回中時計數(shù)電路輸出可能不是 2048，而是有幾個字的偏差；為解13 決這一問題，我們增加了一個方向盤回中檢測電路，系統(tǒng)工作后，數(shù)據(jù)處理電路在模擬器處于非操作狀態(tài)時，系統(tǒng)檢測回中檢測電路，若方向盤處于回中狀態(tài)，而計數(shù)電路的數(shù)據(jù)輸出不是 2048，可對計數(shù)電路進行復位，并重新設置初值。 光電編碼器的應用電路 EPC－ 755A 光電編碼器的應用 EPC－ 755A 光電編碼器具備良好的使用性能，在角度測量、位移測量時抗干擾能力很強，并具有穩(wěn)定可靠的輸出脈沖信號，且該脈沖信號經(jīng)計數(shù)后可得 到被測量的數(shù)字信號。 絕對式編碼器是利用自然二進制 或循環(huán)二進制（葛萊碼）方式進行光電轉(zhuǎn)換的。 增量式編碼器 增量式編碼器是直接利用光電轉(zhuǎn)換原理輸出三組方波脈沖 A、 B 和 Z 相； A、 B 兩組脈沖相位差 90186。low , will change between reciprocating alternate positive and backward pulse, the two counter on the number and replace them when they can eliminate the shadow ring (below instrument readings will involve this). Thus, the clock generator frequency of vibration frequency may be greater than the maximum. Can see from figure 4, a pulse signal of the cycle, four counts pulse. For example, the number of every lap pulse coder for 1000 produce four times the number of pulse frequency, and its resolution is 4000 for degree. Actually, this kind of sensor products will enlarge the output signal of photosensitive 7 ponents such as plastic circuit and sensor encapsulation testing ponents together, so just add subdivision and counts circuit can form a angular measurement system (74159 is 416 decoder). Application problem analysis and improvement measures Application problem analysis Photoelectric detection devices transmit and receive devices are installed in the production and use of exposed many defects, its internal factors have external factors, which is mainly embodied in the following aspects: Devices or accept device for mechanical vibration, caused by the shift or offset, receiving devices not reliable to receive light signals, but cannot produce signals. For example, Photoelectric encoder used in steel rolling speed regulation systems, because of photoelectric encoder is bolted directly in motor shell, photoelectric encoder shaft through hard shrapnal and motor rotor connections, because motor with load is a load of impact, while rolling steel rotor motor will have caused the shell and vibration. According to the mensuration, After steel time electricity encoder vibration velocity for mm/s, this can damage the vibration velocity of photoelectric encoder internal functions. A pulse, thereby causing instability in control system, or misoperation cause accidents. Because of photoelectric detection device installed in production, production environment factors in photoelectric detection devices not reliable work. Such as the installation position of high temperature, humidity, photoelectric detection device to internal electronic ponents characteristics change or damage. For example in continuous caster send tracking system, because of photoelectric detection equipment installation location near the slab, high temperature environment caused by photoelectric detection device signal or damage caused by accidents or production. Production site for all kinds of electromagic interference source photoelectric detection device, of interference, photoelectric detection device of output waveform distortion distortion occurs, the system maloperation accident or production. For example, Photoelectric detection device installed in the production equipment of the signal, the body to the control system of the cable transmission distances in 20100 meters, cable, although usually choose multiple shielded cable conductor, but due to cable capacitance between lines of resistance and impact plus and other cable laying together, vulnerable to all sorts of electroma