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。手持金屬探測器的結(jie)構主要由四部分組成：
1、高頻振蕩器
由(you)三極(ji)(ji)(ji)(ji)管VT1和高(gao)頻(pin)(pin)變(bian)壓(ya)(ya)器(qi)(qi)(qi)T1等組(zu)成，是一(yi)種變(bian)壓(ya)(ya)器(qi)(qi)(qi)反(fan)(fan)饋(kui)(kui)(kui)型LC振(zhen)(zhen)蕩(dang)(dang)器(qi)(qi)(qi)。T1的(de)(de)(de)(de)(de)(de)初級線(xian)圈(quan)(quan)(quan)L1和電(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)C1組(zu)成LC并聯振(zhen)(zhen)蕩(dang)(dang)回路(lu)，其(qi)(qi)振(zhen)(zhen)蕩(dang)(dang)頻(pin)(pin)率(lv)約(yue)200kHz，由(you)L1的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)感量和C1的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)容(rong)(rong)量決(jue)定(ding)(ding)(ding)。T1的(de)(de)(de)(de)(de)(de)次(ci)級線(xian)圈(quan)(quan)(quan)L2作為(wei)(wei)(wei)振(zhen)(zhen)蕩(dang)(dang)器(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)反(fan)(fan)饋(kui)(kui)(kui)線(xian)圈(quan)(quan)(quan)，其(qi)(qi)“C”端接(jie)振(zhen)(zhen)蕩(dang)(dang)管VT1的(de)(de)(de)(de)(de)(de)基(ji)極(ji)(ji)(ji)(ji)，“D”端接(jie)VD2。由(you)于VD2處于正向導通狀態，對(dui)高(gao)頻(pin)(pin)信號來說(shuo)，“D”端可視為(wei)(wei)(wei)接(jie)地。在(zai)高(gao)頻(pin)(pin)變(bian)壓(ya)(ya)器(qi)(qi)(qi)T1中，如果“A” 和“D”端分別為(wei)(wei)(wei)初、次(ci)級線(xian)圈(quan)(quan)(quan)繞線(xian)方向的(de)(de)(de)(de)(de)(de)首端，則從(cong)“C”端輸入到(dao)振(zhen)(zhen)蕩(dang)(dang)管VT1基(ji)極(ji)(ji)(ji)(ji)的(de)(de)(de)(de)(de)(de)反(fan)(fan)饋(kui)(kui)(kui)信號，能(neng)夠(gou)使(shi)電(dian)(dian)(dian)(dian)路(lu)形成正反(fan)(fan)饋(kui)(kui)(kui)而(er)產生自(zi)激(ji)高(gao)頻(pin)(pin)振(zhen)(zhen)蕩(dang)(dang)。振(zhen)(zhen)蕩(dang)(dang)器(qi)(qi)(qi)反(fan)(fan)饋(kui)(kui)(kui)電(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)(de)(de)(de)(de)(de)大小(xiao)與線(xian)圈(quan)(quan)(quan)L1、L2的(de)(de)(de)(de)(de)(de)匝(za)數(shu)比(bi)有(you)關，匝(za)數(shu)比(bi)過(guo)小(xiao)，由(you)于反(fan)(fan)饋(kui)(kui)(kui)太弱，不容(rong)(rong)易(yi)起(qi)(qi)振(zhen)(zhen)，過(guo)大引起(qi)(qi)振(zhen)(zhen)蕩(dang)(dang)波形失(shi)真，還會使(shi)手持金(jin)(jin)屬探測器(qi)(qi)(qi)靈(ling)敏(min)度(du)大為(wei)(wei)(wei)降低。振(zhen)(zhen)蕩(dang)(dang)管VT1的(de)(de)(de)(de)(de)(de)偏置(zhi)電(dian)(dian)(dian)(dian)路(lu)由(you)R2和二(er)極(ji)(ji)(ji)(ji)管VD2組(zu)成，R2為(wei)(wei)(wei)VD2的(de)(de)(de)(de)(de)(de)限(xian)流(liu)電(dian)(dian)(dian)(dian)阻(zu)(zu)。由(you)于二(er)極(ji)(ji)(ji)(ji)管正向閾值電(dian)(dian)(dian)(dian)壓(ya)(ya)恒定(ding)(ding)(ding)（約(yue)0.7V），通過(guo)次(ci)級線(xian)圈(quan)(quan)(quan)L2加到(dao)VT1的(de)(de)(de)(de)(de)(de)基(ji)極(ji)(ji)(ji)(ji)，以(yi)得到(dao)穩(wen)定(ding)(ding)(ding)的(de)(de)(de)(de)(de)(de)偏置(zhi)電(dian)(dian)(dian)(dian)壓(ya)(ya)。顯然，這種穩(wen)壓(ya)(ya)式(shi)的(de)(de)(de)(de)(de)(de)偏置(zhi)電(dian)(dian)(dian)(dian)路(lu)能(neng)夠(gou)大大增強(qiang)VT1高(gao)頻(pin)(pin)振(zhen)(zhen)蕩(dang)(dang)器(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)穩(wen)定(ding)(ding)(ding)性。為(wei)(wei)(wei)了(le)進一(yi)步提高(gao)手持金(jin)(jin)屬探測器(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)可靠性和靈(ling)敏(min)度(du)，高(gao)頻(pin)(pin)振(zhen)(zhen)蕩(dang)(dang)器(qi)(qi)(qi)通過(guo)穩(wen)壓(ya)(ya)電(dian)(dian)(dian)(dian)路(lu)供電(dian)(dian)(dian)(dian)，其(qi)(qi)電(dian)(dian)(dian)(dian)路(lu)由(you)穩(wen)壓(ya)(ya)二(er)極(ji)(ji)(ji)(ji)管VD1、限(xian)流(liu)電(dian)(dian)(dian)(dian)阻(zu)(zu)器(qi)(qi)(qi)R6和去耦電(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)C5組(zu)成。振(zhen)(zhen)蕩(dang)(dang)管VT1發射極(ji)(ji)(ji)(ji)與地之間接(jie)有(you)兩個串聯的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)位器(qi)(qi)(qi)，具有(you)發射極(ji)(ji)(ji)(ji)電(dian)(dian)(dian)(dian)流(liu)負反(fan)(fan)饋(kui)(kui)(kui)作用(yong)，其(qi)(qi)電(dian)(dian)(dian)(dian)阻(zu)(zu)值越大，負反(fan)(fan)饋(kui)(kui)(kui)作用(yong)越強(qiang)，VT1的(de)(de)(de)(de)(de)(de)放大能(neng)力也就越低，甚至(zhi)于使(shi)電(dian)(dian)(dian)(dian)路(lu)停振(zhen)(zhen)。RP1為(wei)(wei)(wei)振(zhen)(zhen)蕩(dang)(dang)器(qi)(qi)(qi)增益(yi)的(de)(de)(de)(de)(de)(de)粗(cu)調電(dian)(dian)(dian)(dian)位器(qi)(qi)(qi)，RP2為(wei)(wei)(wei)細調電(dian)(dian)(dian)(dian)位器(qi)(qi)(qi)。
2、振蕩檢測器
振(zhen)(zhen)蕩(dang)檢(jian)測器(qi)(qi)由三極(ji)(ji)(ji)管(guan)開(kai)關(guan)電(dian)(dian)(dian)(dian)路和濾(lv)波(bo)(bo)(bo)電(dian)(dian)(dian)(dian)路組成(cheng)(cheng)(cheng)。開(kai)關(guan)電(dian)(dian)(dian)(dian)路由三極(ji)(ji)(ji)管(guan)VT2、二極(ji)(ji)(ji)管(guan) VD2等組成(cheng)(cheng)(cheng)，濾(lv)波(bo)(bo)(bo)電(dian)(dian)(dian)(dian)路由濾(lv)波(bo)(bo)(bo)電(dian)(dian)(dian)(dian)阻器(qi)(qi)R3，濾(lv)波(bo)(bo)(bo)電(dian)(dian)(dian)(dian)容器(qi)(qi)C2、C3和C4組成(cheng)(cheng)(cheng)。在(zai)(zai)開(kai)關(guan)電(dian)(dian)(dian)(dian)路中，VT2的基極(ji)(ji)(ji)與次級線(xian)圈(quan)L2的“C”端相連，當(dang)高(gao)(gao)頻振(zhen)(zhen)蕩(dang)器(qi)(qi)工作時(shi)，經高(gao)(gao)頻變壓(ya)器(qi)(qi)T1耦合過(guo)來的振(zhen)(zhen)蕩(dang)信(xin)(xin)號(hao)，正半周使VT2導通，VT2集(ji)電(dian)(dian)(dian)(dian)極(ji)(ji)(ji)輸出負脈沖信(xin)(xin)號(hao)，經過(guo)π型(xing)RC濾(lv)波(bo)(bo)(bo)器(qi)(qi)，在(zai)(zai)負載電(dian)(dian)(dian)(dian)阻器(qi)(qi)R4上(shang)輸出低(di)電(dian)(dian)(dian)(dian)平信(xin)(xin)號(hao)。當(dang)高(gao)(gao)頻振(zhen)(zhen)蕩(dang)器(qi)(qi)停振(zhen)(zhen)蕩(dang)時(shi)，“C”端無振(zhen)(zhen)蕩(dang)信(xin)(xin)號(hao)，又由于二極(ji)(ji)(ji)管(guan)VD2接(jie)在(zai)(zai)VT2發射極(ji)(ji)(ji)與地之(zhi)間，VT2基極(ji)(ji)(ji)被反向偏(pian)置，VT2處(chu)于可(ke)靠的截(jie)止狀態(tai)，VT2集(ji)電(dian)(dian)(dian)(dian)極(ji)(ji)(ji)為高(gao)(gao)電(dian)(dian)(dian)(dian)平，經過(guo)濾(lv)波(bo)(bo)(bo)器(qi)(qi)，在(zai)(zai)R4上(shang)得到高(gao)(gao)電(dian)(dian)(dian)(dian)平信(xin)(xin)號(hao)。由此可(ke)見，當(dang)高(gao)(gao)頻振(zhen)(zhen)蕩(dang)器(qi)(qi)正常工作時(shi)，在(zai)(zai)R4上(shang)得到低(di)電(dian)(dian)(dian)(dian)平信(xin)(xin)號(hao)，停振(zhen)(zhen)時(shi)，為高(gao)(gao)電(dian)(dian)(dian)(dian)平，由此完成(cheng)(cheng)(cheng)了(le)對振(zhen)(zhen)蕩(dang)器(qi)(qi)工作狀態(tai)的檢(jian)測。
3、音頻振蕩器
音頻(pin)振(zhen)蕩(dang)器(qi)(qi)采用(yong)互(hu)補(bu)型(xing)多諧振(zhen)蕩(dang)器(qi)(qi)，由三極管(guan)VT3、VT4，電(dian)(dian)(dian)(dian)(dian)阻器(qi)(qi)R5、R7、 R8和(he)電(dian)(dian)(dian)(dian)(dian)容器(qi)(qi)C6組成。互(hu)補(bu)型(xing)多諧振(zhen)蕩(dang)器(qi)(qi)采用(yong)兩只不同類型(xing)的(de)(de)三極管(guan)，其中VT3為(wei)NPN型(xing)三極管(guan)，VT4為(wei)PNP型(xing)三極管(guan)，連(lian)接成互(hu)補(bu)的(de)(de)、能夠強化正反饋(kui)(kui)的(de)(de)電(dian)(dian)(dian)(dian)(dian)路。在電(dian)(dian)(dian)(dian)(dian)路工(gong)作(zuo)時，它(ta)們(men)能夠交替地進入導(dao)通和(he)截止狀態，產生(sheng)音頻(pin)振(zhen)蕩(dang)。R7既是VT3負載(zai)電(dian)(dian)(dian)(dian)(dian)阻器(qi)(qi)，又(you)是VT3導(dao)通時VT4基極限流(liu)電(dian)(dian)(dian)(dian)(dian)阻器(qi)(qi)。R8是 VT4集電(dian)(dian)(dian)(dian)(dian)極負載(zai)電(dian)(dian)(dian)(dian)(dian)阻器(qi)(qi)，振(zhen)蕩(dang)脈沖(chong)信(xin)號由VT4集電(dian)(dian)(dian)(dian)(dian)極輸出。R5和(he)C6等是反饋(kui)(kui)電(dian)(dian)(dian)(dian)(dian)阻器(qi)(qi)和(he)電(dian)(dian)(dian)(dian)(dian)容器(qi)(qi)，其數值大小影(ying)響振(zhen)蕩(dang)頻(pin)率的(de)(de)高低。
4、功率放大器
功率(lv)放大器(qi)(qi)由(you)三極管VT5、揚(yang)(yang)聲(sheng)器(qi)(qi)BL等組成。從多(duo)諧振(zhen)蕩器(qi)(qi)輸(shu)(shu)出的正脈沖(chong)音頻信號經限流電阻(zu)器(qi)(qi)R9輸(shu)(shu)入到VT5的基(ji)極，使其導通(tong)，在BL產生瞬時(shi)較強的電流，驅動揚(yang)(yang)聲(sheng)器(qi)(qi)發聲(sheng)。由(you)于(yu)(yu)VT5處于(yu)(yu)開(kai)關工作狀態，而(er)導通(tong)時(shi)間又非常(chang)短，因此功率(lv)放大器(qi)(qi)非常(chang)省電，可以(yi)利(li)用(yong)9V積(ji)層電池(chi)供(gong)電。
二、手持式金屬探測器原理是什么
了(le)解(jie)了(le)手(shou)持金(jin)屬探測器(qi)的(de)結構，接(jie)下來就可以介紹金(jin)屬探測器(qi)的(de)工作原理了(le)：
手持金屬探測器利(li)用電磁感(gan)應的(de)原(yuan)(yuan)理，利(li)用有(you)交(jiao)流(liu)電通(tong)過(guo)的(de)線圈，產(chan)生迅速變化的(de)磁場(chang)。這個磁場(chang)能(neng)在金屬物(wu)體內(nei)部能(neng)感(gan)生渦(wo)電流(liu)。渦(wo)電流(liu)又(you)會產(chan)生磁場(chang)，倒(dao)過(guo)來(lai)影響原(yuan)(yuan)來(lai)的(de)磁場(chang)，引發探測器發出鳴聲。
工作時(shi)，其(qi)內(nei)部探測器會發出(chu)某(mou)一(yi)頻(pin)(pin)率的(de)電(dian)磁波，由于金(jin)屬有自感(gan)，會使(shi)這一(yi)頻(pin)(pin)率發生偏移，當它再(zai)接收到有偏差的(de)電(dian)磁波時(shi)，就把差頻(pin)(pin)放(fang)大，發出(chu)信號報警。
