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)結構主要由四部分組成：
1、高頻振蕩器
由(you)(you)三極(ji)(ji)管VT1和(he)(he)(he)高(gao)(gao)頻(pin)(pin)變(bian)壓(ya)器(qi)(qi)(qi)T1等組成(cheng)，是(shi)一種變(bian)壓(ya)器(qi)(qi)(qi)反(fan)饋(kui)型(xing)LC振(zhen)蕩(dang)器(qi)(qi)(qi)。T1的(de)(de)(de)(de)初級線(xian)(xian)圈(quan)(quan)L1和(he)(he)(he)電(dian)(dian)(dian)(dian)容(rong)器(qi)(qi)(qi)C1組成(cheng)LC并聯振(zhen)蕩(dang)回(hui)路(lu)(lu)，其(qi)振(zhen)蕩(dang)頻(pin)(pin)率約200kHz，由(you)(you)L1的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)感量(liang)和(he)(he)(he)C1的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)容(rong)量(liang)決定(ding)。T1的(de)(de)(de)(de)次(ci)級線(xian)(xian)圈(quan)(quan)L2作為(wei)振(zhen)蕩(dang)器(qi)(qi)(qi)的(de)(de)(de)(de)反(fan)饋(kui)線(xian)(xian)圈(quan)(quan)，其(qi)“C”端接振(zhen)蕩(dang)管VT1的(de)(de)(de)(de)基(ji)極(ji)(ji)，“D”端接VD2。由(you)(you)于VD2處(chu)于正向導通狀態，對(dui)高(gao)(gao)頻(pin)(pin)信(xin)號(hao)來說，“D”端可視(shi)為(wei)接地。在(zai)高(gao)(gao)頻(pin)(pin)變(bian)壓(ya)器(qi)(qi)(qi)T1中，如果“A” 和(he)(he)(he)“D”端分別為(wei)初、次(ci)級線(xian)(xian)圈(quan)(quan)繞線(xian)(xian)方向的(de)(de)(de)(de)首端，則(ze)從“C”端輸入到(dao)振(zhen)蕩(dang)管VT1基(ji)極(ji)(ji)的(de)(de)(de)(de)反(fan)饋(kui)信(xin)號(hao)，能夠使(shi)電(dian)(dian)(dian)(dian)路(lu)(lu)形成(cheng)正反(fan)饋(kui)而產生自激(ji)高(gao)(gao)頻(pin)(pin)振(zhen)蕩(dang)。振(zhen)蕩(dang)器(qi)(qi)(qi)反(fan)饋(kui)電(dian)(dian)(dian)(dian)壓(ya)的(de)(de)(de)(de)大(da)(da)(da)小與線(xian)(xian)圈(quan)(quan)L1、L2的(de)(de)(de)(de)匝數比有關，匝數比過(guo)小，由(you)(you)于反(fan)饋(kui)太弱，不容(rong)易(yi)起(qi)振(zhen)，過(guo)大(da)(da)(da)引起(qi)振(zhen)蕩(dang)波形失真，還(huan)會使(shi)手(shou)持金屬(shu)探測器(qi)(qi)(qi)靈敏度(du)大(da)(da)(da)為(wei)降低。振(zhen)蕩(dang)管VT1的(de)(de)(de)(de)偏置電(dian)(dian)(dian)(dian)路(lu)(lu)由(you)(you)R2和(he)(he)(he)二(er)極(ji)(ji)管VD2組成(cheng)，R2為(wei)VD2的(de)(de)(de)(de)限流電(dian)(dian)(dian)(dian)阻(zu)。由(you)(you)于二(er)極(ji)(ji)管正向閾值電(dian)(dian)(dian)(dian)壓(ya)恒定(ding)（約0.7V），通過(guo)次(ci)級線(xian)(xian)圈(quan)(quan)L2加到(dao)VT1的(de)(de)(de)(de)基(ji)極(ji)(ji)，以得到(dao)穩(wen)定(ding)的(de)(de)(de)(de)偏置電(dian)(dian)(dian)(dian)壓(ya)。顯然，這(zhe)種穩(wen)壓(ya)式的(de)(de)(de)(de)偏置電(dian)(dian)(dian)(dian)路(lu)(lu)能夠大(da)(da)(da)大(da)(da)(da)增強(qiang)VT1高(gao)(gao)頻(pin)(pin)振(zhen)蕩(dang)器(qi)(qi)(qi)的(de)(de)(de)(de)穩(wen)定(ding)性。為(wei)了進一步提高(gao)(gao)手(shou)持金屬(shu)探測器(qi)(qi)(qi)的(de)(de)(de)(de)可靠(kao)性和(he)(he)(he)靈敏度(du)，高(gao)(gao)頻(pin)(pin)振(zhen)蕩(dang)器(qi)(qi)(qi)通過(guo)穩(wen)壓(ya)電(dian)(dian)(dian)(dian)路(lu)(lu)供(gong)電(dian)(dian)(dian)(dian)，其(qi)電(dian)(dian)(dian)(dian)路(lu)(lu)由(you)(you)穩(wen)壓(ya)二(er)極(ji)(ji)管VD1、限流電(dian)(dian)(dian)(dian)阻(zu)器(qi)(qi)(qi)R6和(he)(he)(he)去(qu)耦電(dian)(dian)(dian)(dian)容(rong)器(qi)(qi)(qi)C5組成(cheng)。振(zhen)蕩(dang)管VT1發射極(ji)(ji)與地之間接有兩個(ge)串(chuan)聯的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)位(wei)(wei)器(qi)(qi)(qi)，具有發射極(ji)(ji)電(dian)(dian)(dian)(dian)流負反(fan)饋(kui)作用，其(qi)電(dian)(dian)(dian)(dian)阻(zu)值越大(da)(da)(da)，負反(fan)饋(kui)作用越強(qiang)，VT1的(de)(de)(de)(de)放大(da)(da)(da)能力(li)也就(jiu)越低，甚(shen)至于使(shi)電(dian)(dian)(dian)(dian)路(lu)(lu)停振(zhen)。RP1為(wei)振(zhen)蕩(dang)器(qi)(qi)(qi)增益的(de)(de)(de)(de)粗調(diao)電(dian)(dian)(dian)(dian)位(wei)(wei)器(qi)(qi)(qi)，RP2為(wei)細調(diao)電(dian)(dian)(dian)(dian)位(wei)(wei)器(qi)(qi)(qi)。
2、振蕩檢測器
振(zhen)(zhen)蕩(dang)(dang)檢測器(qi)(qi)由(you)三極(ji)管開(kai)關電(dian)(dian)(dian)(dian)路(lu)和濾(lv)(lv)波(bo)(bo)電(dian)(dian)(dian)(dian)路(lu)組成。開(kai)關電(dian)(dian)(dian)(dian)路(lu)由(you)三極(ji)管VT2、二極(ji)管 VD2等組成，濾(lv)(lv)波(bo)(bo)電(dian)(dian)(dian)(dian)路(lu)由(you)濾(lv)(lv)波(bo)(bo)電(dian)(dian)(dian)(dian)阻器(qi)(qi)R3，濾(lv)(lv)波(bo)(bo)電(dian)(dian)(dian)(dian)容器(qi)(qi)C2、C3和C4組成。在(zai)開(kai)關電(dian)(dian)(dian)(dian)路(lu)中，VT2的(de)(de)(de)(de)基極(ji)與(yu)次級線圈L2的(de)(de)(de)(de)“C”端相連，當(dang)高頻振(zhen)(zhen)蕩(dang)(dang)器(qi)(qi)工作(zuo)時(shi)，經高頻變壓器(qi)(qi)T1耦合過來的(de)(de)(de)(de)振(zhen)(zhen)蕩(dang)(dang)信(xin)(xin)(xin)號(hao)(hao)，正(zheng)半周使VT2導通，VT2集電(dian)(dian)(dian)(dian)極(ji)輸(shu)出(chu)負脈沖信(xin)(xin)(xin)號(hao)(hao)，經過π型(xing)RC濾(lv)(lv)波(bo)(bo)器(qi)(qi)，在(zai)負載電(dian)(dian)(dian)(dian)阻器(qi)(qi)R4上輸(shu)出(chu)低(di)電(dian)(dian)(dian)(dian)平(ping)信(xin)(xin)(xin)號(hao)(hao)。當(dang)高頻振(zhen)(zhen)蕩(dang)(dang)器(qi)(qi)停振(zhen)(zhen)蕩(dang)(dang)時(shi)，“C”端無振(zhen)(zhen)蕩(dang)(dang)信(xin)(xin)(xin)號(hao)(hao)，又由(you)于(yu)二極(ji)管VD2接(jie)在(zai)VT2發(fa)射極(ji)與(yu)地之間，VT2基極(ji)被反向偏置，VT2處于(yu)可靠的(de)(de)(de)(de)截止狀(zhuang)態，VT2集電(dian)(dian)(dian)(dian)極(ji)為高電(dian)(dian)(dian)(dian)平(ping)，經過濾(lv)(lv)波(bo)(bo)器(qi)(qi)，在(zai)R4上得到高電(dian)(dian)(dian)(dian)平(ping)信(xin)(xin)(xin)號(hao)(hao)。由(you)此可見，當(dang)高頻振(zhen)(zhen)蕩(dang)(dang)器(qi)(qi)正(zheng)常(chang)工作(zuo)時(shi)，在(zai)R4上得到低(di)電(dian)(dian)(dian)(dian)平(ping)信(xin)(xin)(xin)號(hao)(hao)，停振(zhen)(zhen)時(shi)，為高電(dian)(dian)(dian)(dian)平(ping)，由(you)此完成了對振(zhen)(zhen)蕩(dang)(dang)器(qi)(qi)工作(zuo)狀(zhuang)態的(de)(de)(de)(de)檢測。
3、音頻振蕩器
音頻(pin)振蕩(dang)(dang)器(qi)(qi)(qi)采用互(hu)(hu)補(bu)型(xing)(xing)多諧(xie)振蕩(dang)(dang)器(qi)(qi)(qi)，由三極(ji)管VT3、VT4，電(dian)阻(zu)器(qi)(qi)(qi)R5、R7、 R8和電(dian)容(rong)器(qi)(qi)(qi)C6組成。互(hu)(hu)補(bu)型(xing)(xing)多諧(xie)振蕩(dang)(dang)器(qi)(qi)(qi)采用兩只不同類型(xing)(xing)的(de)三極(ji)管，其中VT3為NPN型(xing)(xing)三極(ji)管，VT4為PNP型(xing)(xing)三極(ji)管，連接成互(hu)(hu)補(bu)的(de)、能夠強(qiang)化正反饋的(de)電(dian)路(lu)。在電(dian)路(lu)工作時(shi)，它們能夠交替地進入導通和截止狀態，產生音頻(pin)振蕩(dang)(dang)。R7既是(shi)VT3負載(zai)(zai)電(dian)阻(zu)器(qi)(qi)(qi)，又是(shi)VT3導通時(shi)VT4基極(ji)限流(liu)電(dian)阻(zu)器(qi)(qi)(qi)。R8是(shi) VT4集電(dian)極(ji)負載(zai)(zai)電(dian)阻(zu)器(qi)(qi)(qi)，振蕩(dang)(dang)脈沖信號由VT4集電(dian)極(ji)輸出。R5和C6等是(shi)反饋電(dian)阻(zu)器(qi)(qi)(qi)和電(dian)容(rong)器(qi)(qi)(qi)，其數(shu)值(zhi)大小影響振蕩(dang)(dang)頻(pin)率(lv)的(de)高低。
4、功率放大器
功(gong)率(lv)(lv)放(fang)大(da)器(qi)(qi)由三極管VT5、揚聲(sheng)器(qi)(qi)BL等組成。從多諧振蕩器(qi)(qi)輸出的(de)正脈(mo)沖音頻信號經限流電(dian)阻(zu)器(qi)(qi)R9輸入(ru)到(dao)VT5的(de)基(ji)極，使其導通(tong)，在BL產生瞬時(shi)較(jiao)強(qiang)的(de)電(dian)流，驅(qu)動揚聲(sheng)器(qi)(qi)發聲(sheng)。由于VT5處于開關(guan)工作狀態，而導通(tong)時(shi)間(jian)又(you)非(fei)常(chang)短(duan)，因此(ci)功(gong)率(lv)(lv)放(fang)大(da)器(qi)(qi)非(fei)常(chang)省電(dian)，可以利用9V積層電(dian)池供電(dian)。
二、手持式金屬探測器原理是什么
了(le)解了(le)手持金屬探測器的(de)結(jie)構，接下來就可以介紹金屬探測器的(de)工作(zuo)原理了(le)：
手持金屬探測器利(li)用電(dian)磁(ci)(ci)感(gan)應的(de)(de)(de)原理，利(li)用有交流電(dian)通過的(de)(de)(de)線圈(quan)，產生(sheng)迅速變化的(de)(de)(de)磁(ci)(ci)場。這個磁(ci)(ci)場能在金屬物體內部能感(gan)生(sheng)渦電(dian)流。渦電(dian)流又會(hui)產生(sheng)磁(ci)(ci)場，倒(dao)過來(lai)影(ying)響原來(lai)的(de)(de)(de)磁(ci)(ci)場，引發(fa)探(tan)測器(qi)發(fa)出鳴聲。
工作時，其內部探測器會發(fa)出某一頻(pin)(pin)率(lv)的電(dian)磁(ci)波，由于金屬有(you)自感，會使這一頻(pin)(pin)率(lv)發(fa)生偏(pian)移，當(dang)它再接收到有(you)偏(pian)差的電(dian)磁(ci)波時，就把(ba)差頻(pin)(pin)放大，發(fa)出信(xin)號報(bao)警。
