一、手持金屬探測儀由哪幾部分組成
手持式金屬探測器被設計用來探測人或物體攜帶的金屬物，廣泛應用于安全檢查、考古、探礦等方面。手持金屬探測器的(de)結構主(zhu)要由(you)四部分組成：
1、高頻振蕩器
由(you)(you)三極(ji)(ji)管(guan)VT1和高(gao)(gao)(gao)頻(pin)變壓(ya)器(qi)T1等組成(cheng)，是一種變壓(ya)器(qi)反(fan)(fan)饋(kui)型LC振(zhen)蕩器(qi)。T1的(de)(de)(de)(de)(de)初級線(xian)(xian)(xian)圈(quan)L1和電(dian)(dian)(dian)(dian)(dian)容(rong)器(qi)C1組成(cheng)LC并聯振(zhen)蕩回路，其(qi)(qi)振(zhen)蕩頻(pin)率(lv)約200kHz，由(you)(you)L1的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)感量(liang)(liang)和C1的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)容(rong)量(liang)(liang)決定。T1的(de)(de)(de)(de)(de)次級線(xian)(xian)(xian)圈(quan)L2作(zuo)(zuo)為(wei)(wei)振(zhen)蕩器(qi)的(de)(de)(de)(de)(de)反(fan)(fan)饋(kui)線(xian)(xian)(xian)圈(quan)，其(qi)(qi)“C”端(duan)(duan)接振(zhen)蕩管(guan)VT1的(de)(de)(de)(de)(de)基(ji)極(ji)(ji)，“D”端(duan)(duan)接VD2。由(you)(you)于(yu)VD2處于(yu)正向(xiang)導通(tong)狀態(tai)，對高(gao)(gao)(gao)頻(pin)信(xin)號(hao)來說，“D”端(duan)(duan)可(ke)視為(wei)(wei)接地。在高(gao)(gao)(gao)頻(pin)變壓(ya)器(qi)T1中，如(ru)果(guo)“A” 和“D”端(duan)(duan)分別為(wei)(wei)初、次級線(xian)(xian)(xian)圈(quan)繞線(xian)(xian)(xian)方(fang)向(xiang)的(de)(de)(de)(de)(de)首端(duan)(duan)，則從(cong)“C”端(duan)(duan)輸入到振(zhen)蕩管(guan)VT1基(ji)極(ji)(ji)的(de)(de)(de)(de)(de)反(fan)(fan)饋(kui)信(xin)號(hao)，能(neng)夠(gou)使(shi)電(dian)(dian)(dian)(dian)(dian)路形(xing)成(cheng)正反(fan)(fan)饋(kui)而(er)產生自激高(gao)(gao)(gao)頻(pin)振(zhen)蕩。振(zhen)蕩器(qi)反(fan)(fan)饋(kui)電(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)(de)(de)(de)(de)大(da)小與線(xian)(xian)(xian)圈(quan)L1、L2的(de)(de)(de)(de)(de)匝數(shu)比(bi)有關，匝數(shu)比(bi)過(guo)(guo)小，由(you)(you)于(yu)反(fan)(fan)饋(kui)太弱，不容(rong)易(yi)起(qi)振(zhen)，過(guo)(guo)大(da)引起(qi)振(zhen)蕩波形(xing)失(shi)真，還會(hui)使(shi)手持金屬探測器(qi)靈(ling)敏度大(da)為(wei)(wei)降低(di)。振(zhen)蕩管(guan)VT1的(de)(de)(de)(de)(de)偏(pian)置(zhi)電(dian)(dian)(dian)(dian)(dian)路由(you)(you)R2和二極(ji)(ji)管(guan)VD2組成(cheng)，R2為(wei)(wei)VD2的(de)(de)(de)(de)(de)限流電(dian)(dian)(dian)(dian)(dian)阻。由(you)(you)于(yu)二極(ji)(ji)管(guan)正向(xiang)閾值(zhi)(zhi)電(dian)(dian)(dian)(dian)(dian)壓(ya)恒定（約0.7V），通(tong)過(guo)(guo)次級線(xian)(xian)(xian)圈(quan)L2加(jia)到VT1的(de)(de)(de)(de)(de)基(ji)極(ji)(ji)，以得到穩定的(de)(de)(de)(de)(de)偏(pian)置(zhi)電(dian)(dian)(dian)(dian)(dian)壓(ya)。顯然，這(zhe)種穩壓(ya)式(shi)的(de)(de)(de)(de)(de)偏(pian)置(zhi)電(dian)(dian)(dian)(dian)(dian)路能(neng)夠(gou)大(da)大(da)增強(qiang)VT1高(gao)(gao)(gao)頻(pin)振(zhen)蕩器(qi)的(de)(de)(de)(de)(de)穩定性(xing)。為(wei)(wei)了進一步提高(gao)(gao)(gao)手持金屬探測器(qi)的(de)(de)(de)(de)(de)可(ke)靠性(xing)和靈(ling)敏度，高(gao)(gao)(gao)頻(pin)振(zhen)蕩器(qi)通(tong)過(guo)(guo)穩壓(ya)電(dian)(dian)(dian)(dian)(dian)路供電(dian)(dian)(dian)(dian)(dian)，其(qi)(qi)電(dian)(dian)(dian)(dian)(dian)路由(you)(you)穩壓(ya)二極(ji)(ji)管(guan)VD1、限流電(dian)(dian)(dian)(dian)(dian)阻器(qi)R6和去耦電(dian)(dian)(dian)(dian)(dian)容(rong)器(qi)C5組成(cheng)。振(zhen)蕩管(guan)VT1發射極(ji)(ji)與地之間(jian)接有兩個(ge)串聯的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)位器(qi)，具有發射極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)流負反(fan)(fan)饋(kui)作(zuo)(zuo)用，其(qi)(qi)電(dian)(dian)(dian)(dian)(dian)阻值(zhi)(zhi)越大(da)，負反(fan)(fan)饋(kui)作(zuo)(zuo)用越強(qiang)，VT1的(de)(de)(de)(de)(de)放大(da)能(neng)力(li)也就越低(di)，甚(shen)至于(yu)使(shi)電(dian)(dian)(dian)(dian)(dian)路停振(zhen)。RP1為(wei)(wei)振(zhen)蕩器(qi)增益的(de)(de)(de)(de)(de)粗調電(dian)(dian)(dian)(dian)(dian)位器(qi)，RP2為(wei)(wei)細調電(dian)(dian)(dian)(dian)(dian)位器(qi)。
2、振蕩檢測器
振(zhen)蕩(dang)檢(jian)測(ce)器(qi)(qi)(qi)由(you)三(san)極(ji)(ji)(ji)管(guan)開(kai)關電(dian)(dian)(dian)(dian)路(lu)(lu)和濾波(bo)電(dian)(dian)(dian)(dian)路(lu)(lu)組成(cheng)(cheng)。開(kai)關電(dian)(dian)(dian)(dian)路(lu)(lu)由(you)三(san)極(ji)(ji)(ji)管(guan)VT2、二(er)極(ji)(ji)(ji)管(guan) VD2等組成(cheng)(cheng)，濾波(bo)電(dian)(dian)(dian)(dian)路(lu)(lu)由(you)濾波(bo)電(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)R3，濾波(bo)電(dian)(dian)(dian)(dian)容器(qi)(qi)(qi)C2、C3和C4組成(cheng)(cheng)。在(zai)(zai)開(kai)關電(dian)(dian)(dian)(dian)路(lu)(lu)中，VT2的(de)(de)(de)基極(ji)(ji)(ji)與(yu)次級線圈L2的(de)(de)(de)“C”端(duan)相(xiang)連(lian)，當(dang)高(gao)頻振(zhen)蕩(dang)器(qi)(qi)(qi)工作(zuo)時(shi)，經(jing)高(gao)頻變壓器(qi)(qi)(qi)T1耦合過來的(de)(de)(de)振(zhen)蕩(dang)信號(hao)(hao)(hao)，正半(ban)周使VT2導通(tong)，VT2集(ji)電(dian)(dian)(dian)(dian)極(ji)(ji)(ji)輸(shu)出負脈沖(chong)信號(hao)(hao)(hao)，經(jing)過π型RC濾波(bo)器(qi)(qi)(qi)，在(zai)(zai)負載電(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)R4上(shang)輸(shu)出低電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)信號(hao)(hao)(hao)。當(dang)高(gao)頻振(zhen)蕩(dang)器(qi)(qi)(qi)停振(zhen)蕩(dang)時(shi)，“C”端(duan)無振(zhen)蕩(dang)信號(hao)(hao)(hao)，又由(you)于二(er)極(ji)(ji)(ji)管(guan)VD2接(jie)在(zai)(zai)VT2發射(she)極(ji)(ji)(ji)與(yu)地之(zhi)間，VT2基極(ji)(ji)(ji)被反(fan)向偏置，VT2處(chu)于可(ke)靠(kao)的(de)(de)(de)截(jie)止狀態，VT2集(ji)電(dian)(dian)(dian)(dian)極(ji)(ji)(ji)為(wei)高(gao)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，經(jing)過濾波(bo)器(qi)(qi)(qi)，在(zai)(zai)R4上(shang)得到高(gao)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)信號(hao)(hao)(hao)。由(you)此可(ke)見，當(dang)高(gao)頻振(zhen)蕩(dang)器(qi)(qi)(qi)正常工作(zuo)時(shi)，在(zai)(zai)R4上(shang)得到低電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)信號(hao)(hao)(hao)，停振(zhen)時(shi)，為(wei)高(gao)電(dian)(dian)(dian)(dian)平(ping)(ping)(ping)，由(you)此完成(cheng)(cheng)了對振(zhen)蕩(dang)器(qi)(qi)(qi)工作(zuo)狀態的(de)(de)(de)檢(jian)測(ce)。
3、音頻振蕩器
音(yin)(yin)頻振(zhen)蕩(dang)(dang)器(qi)采用(yong)互補(bu)型(xing)多諧(xie)(xie)振(zhen)蕩(dang)(dang)器(qi)，由(you)三(san)極(ji)(ji)管(guan)VT3、VT4，電(dian)(dian)(dian)(dian)阻(zu)器(qi)R5、R7、 R8和(he)電(dian)(dian)(dian)(dian)容器(qi)C6組成。互補(bu)型(xing)多諧(xie)(xie)振(zhen)蕩(dang)(dang)器(qi)采用(yong)兩只不同類型(xing)的(de)三(san)極(ji)(ji)管(guan)，其(qi)(qi)中VT3為NPN型(xing)三(san)極(ji)(ji)管(guan)，VT4為PNP型(xing)三(san)極(ji)(ji)管(guan)，連接成互補(bu)的(de)、能(neng)夠強化正反饋(kui)(kui)的(de)電(dian)(dian)(dian)(dian)路。在電(dian)(dian)(dian)(dian)路工作時(shi)(shi)，它們能(neng)夠交替地(di)進入導通和(he)截(jie)止狀態，產生音(yin)(yin)頻振(zhen)蕩(dang)(dang)。R7既是(shi)(shi)VT3負載電(dian)(dian)(dian)(dian)阻(zu)器(qi)，又是(shi)(shi)VT3導通時(shi)(shi)VT4基極(ji)(ji)限流電(dian)(dian)(dian)(dian)阻(zu)器(qi)。R8是(shi)(shi) VT4集(ji)電(dian)(dian)(dian)(dian)極(ji)(ji)負載電(dian)(dian)(dian)(dian)阻(zu)器(qi)，振(zhen)蕩(dang)(dang)脈沖信號由(you)VT4集(ji)電(dian)(dian)(dian)(dian)極(ji)(ji)輸出。R5和(he)C6等是(shi)(shi)反饋(kui)(kui)電(dian)(dian)(dian)(dian)阻(zu)器(qi)和(he)電(dian)(dian)(dian)(dian)容器(qi)，其(qi)(qi)數值(zhi)大小影(ying)響振(zhen)蕩(dang)(dang)頻率的(de)高低。
4、功率放大器
功率放大器(qi)(qi)由三極管(guan)VT5、揚(yang)聲器(qi)(qi)BL等組成。從多(duo)諧(xie)振蕩器(qi)(qi)輸出的正(zheng)脈(mo)沖音頻(pin)信號(hao)經限流電阻器(qi)(qi)R9輸入到VT5的基極，使其(qi)導(dao)(dao)通(tong)，在BL產(chan)生(sheng)瞬時較強(qiang)的電流，驅(qu)動揚(yang)聲器(qi)(qi)發聲。由于VT5處于開關工作狀態，而(er)導(dao)(dao)通(tong)時間又(you)非常(chang)短，因(yin)此功率放大器(qi)(qi)非常(chang)省電，可以(yi)利用9V積層電池(chi)供電。
二、手持式金屬探測器原理是什么
了解(jie)了手持金(jin)屬(shu)探測器(qi)的結構，接下來就可以介紹金(jin)屬(shu)探測器(qi)的工作原(yuan)理了：
手持金屬探測器利用(yong)電(dian)磁感應的原理，利用(yong)有交流電(dian)通過的線圈，產生(sheng)(sheng)迅速(su)變(bian)化的磁場。這(zhe)個磁場能在金屬物體(ti)內部能感生(sheng)(sheng)渦(wo)電(dian)流。渦(wo)電(dian)流又會產生(sheng)(sheng)磁場，倒過來影響原來的磁場，引(yin)發(fa)探測器發(fa)出鳴聲。
工(gong)作時，其內部(bu)探測器(qi)會(hui)發(fa)(fa)出某一(yi)頻(pin)(pin)率(lv)的電磁波(bo)，由于金屬有自感，會(hui)使這一(yi)頻(pin)(pin)率(lv)發(fa)(fa)生偏(pian)移，當它再接收到有偏(pian)差(cha)的電磁波(bo)時，就把(ba)差(cha)頻(pin)(pin)放大，發(fa)(fa)出信(xin)號(hao)報警。
