【文章內(nèi)容簡介】 時鐘脈沖輸入。測試儀停止工作。 第四章 總原理圖及原理綜述數(shù)字脈搏測試儀總原理圖如圖12所示。壓電陶瓷片HTD27將拾取的脈搏跳動信號轉(zhuǎn)換成電信號，經(jīng)CD4011B組成的四級線性放大器放大后，送到由CD4553和CD4511組成的計數(shù)譯碼顯示電路。CD4553內(nèi)部輸入端設(shè)置了脈沖整形電路，所以對脈沖沿?zé)o甚特殊要求。它只有一組BCD碼輸出，但通過內(nèi)部分時控制可形成三位十進制數(shù)字顯示。CD4511是譯碼器，其輸出驅(qū)動三位LED共陰數(shù)碼管。BGBGBG3分別由CD4553的12腳控制實現(xiàn)三位數(shù)碼管的分時顯示。 使用時，用手表帶或松緊帶將壓電陶瓷片壓在手腕的撓動脈處，注意一定要壓緊。在合上開關(guān)K1后即按一下復(fù)位開關(guān)K2，使CD4060和CD4553清零，這時計數(shù)閘門打開，脈搏信號由CD4553進行計數(shù)。1分鐘后，CD4060輸出一高電平，使計數(shù)閘門關(guān)閉。這時數(shù)碼管顯示的數(shù)字即為每分鐘的脈搏數(shù)。圖12總體調(diào)試將壓電陶瓷片緊壓在手腕的脈搏處，而后接通電源開關(guān)S，數(shù)碼顯示管將顯示數(shù)字，表明電路工作正常，緊接著按下清零按鈕S1，則數(shù)碼管計數(shù)值將隨著脈搏的跳而持續(xù)增加，當(dāng)1分鐘后，由于定時器的原因，數(shù)值被鎖存，數(shù)碼管顯示當(dāng)時的數(shù)值，此計數(shù)值，即為每分鐘的脈搏次數(shù)。調(diào)試放大整形電路 用脈沖信號發(fā)生器做輸入信號源，用脈沖示波器觀測放大電路和整形電路輸出端電壓波形，正常情況下應(yīng)有100倍以上的放大，整形電路應(yīng)輸出理想的電壓波形。調(diào)試計數(shù)顯示電路 用低頻脈沖信號發(fā)生器的輸出信號作為計數(shù)器的輸入，從LED數(shù)碼管上去讀數(shù)字，觀察個，十位計數(shù)器是否都能完成逢十進一的功能，然后按下清零按鈕，使兩個計數(shù)器均清零，重新開始計數(shù)，數(shù)碼管應(yīng)能反映這個狀態(tài)。如果讀取出錯，要檢查2個數(shù)碼管的連線是否正確，所以必須檢查譯碼器各輸出端與數(shù)碼管相應(yīng)引腳的連接是否正確。設(shè)計心得與體會心得：本次設(shè)計模塊設(shè)計中要通過關(guān)聯(lián)譯碼器CD451由三個同步級聯(lián)的下降沿觸發(fā)的BCD計數(shù)器（個位、十位、百位）、三個鎖存器、分配鎖存器數(shù)據(jù)的多路轉(zhuǎn)換器、輸入整形電路、時序掃描電路及振蕩電路等部分組成的多功能CD4553和PNP三極管的分時控制部分組成，在此設(shè)計中的難點主要有：根據(jù)CD4533的15管腳的輸出電平關(guān)系選擇一個能在低電平輸入的情況下，通過控制數(shù)碼管的共陰極部分，從而實現(xiàn)片選、分時控制的功能。CD4553通過輸入的脈沖信號經(jīng)過整形后進行計數(shù)再通過編碼輸出到一個譯碼器芯片CD4511，此譯碼器通過與CD4553的結(jié)合控制快速顯示。體會：在摸索該如何設(shè)計電路使之實現(xiàn)所需功能的過程中，特別有趣，培養(yǎng)了我的設(shè)計思維，增加了實際操作能力。我覺得以后更要加強這方面的設(shè)計。，書本上的知識有了用武之地，這鞏固和深化了自己的知識結(jié)構(gòu)。這次課設(shè)恰恰給我提供了一個應(yīng)用自己所學(xué)知識的機會，從到圖書館、網(wǎng)上查找資料到對電路的設(shè)計對電路定位的再到最后電路的成型，都對我所學(xué)的知識進行了檢驗?？梢哉f，本次設(shè)計有苦也有甜。 設(shè)計思路是最重要的，只要你的設(shè)計思路是成功的，那你的設(shè)計已經(jīng)成功了一半。因此我們應(yīng)該在設(shè)計前做好充分的準(zhǔn)備。我們要熟練地掌握課本上的知識，這樣才能對試驗中出現(xiàn)的問題進行分析解決。 留給我印象最深的是要設(shè)計一個成功的電路，必須要有耐心，要有堅持的毅力。參考文獻：《數(shù)字電子技術(shù)基礎(chǔ)》，閻石編，高教出版社?！赌M電子技術(shù)》，江曉安編，西電出版社?！稊?shù)字電子技術(shù)》，江曉安編，西電出版社?！稛o線電》雜志，《電子制作》雜志?！峨娮蛹夹g(shù)工藝基礎(chǔ)》王天曦、李鴻儒編，北京清華大學(xué)出版社 2004年 《模擬電子技術(shù)》胡宴如，北京高等教育出版社 2002年 標(biāo)準(zhǔn)數(shù)字電路 4000 CMOS 全系列數(shù)據(jù)手冊 《傳感器與檢測技術(shù)》謝志萍，北京電子工業(yè)出版社 2005年 致謝g an employment tribunal claimEmployment tribunals sort out disagreements between employers and employees.You may need to make a claim to an employment tribunal if: you don39。t agree with the disciplinary action your employer has taken against you your employer dismisses you and you think that you have been dismissed unfairly.For more information about dismissal and unfair dismissal, seeDismissal.You can make a claim to an employment tribunal, even if you haven39。tappealedagainst the disciplinary action your employer has taken against you. However, if you win your case, the tribunal may reduce any pensation awarded to you as a result of your failure to appeal.Remember that in most cases you must make an application to an employment tribunal within three months of the date when the event you are plaining about happened. If your application is received after this time limit, the tribunal will not usually accept it.If you are worried about how the time limits apply to you, take advice from one of the organisations listed underFurther help.Employment tribunals are less formal than some other courts, but it is still a legal process and you will need to give evidence under an oath or affirmation.Most people find making a claim to an employment tribunal challenging. If you are thinking about making a claim to an employment tribunal, you should get help straight away from one of the organisations listed underFurther help.If you are being represented by a solicitor at the tribunal, they may ask you to sign an agreement where you pay their fee out of y