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構主要由四部分組成(cheng)：
1、高頻振蕩器
由(you)三極(ji)(ji)管(guan)(guan)(guan)VT1和(he)(he)高(gao)(gao)頻(pin)(pin)(pin)變壓器(qi)(qi)(qi)(qi)T1等組成(cheng)，是一(yi)種變壓器(qi)(qi)(qi)(qi)反(fan)饋(kui)(kui)型LC振(zhen)(zhen)蕩(dang)器(qi)(qi)(qi)(qi)。T1的(de)(de)初級(ji)(ji)線圈L1和(he)(he)電(dian)(dian)(dian)(dian)容器(qi)(qi)(qi)(qi)C1組成(cheng)LC并(bing)聯振(zhen)(zhen)蕩(dang)回路(lu)，其振(zhen)(zhen)蕩(dang)頻(pin)(pin)(pin)率約(yue)200kHz，由(you)L1的(de)(de)電(dian)(dian)(dian)(dian)感(gan)量(liang)和(he)(he)C1的(de)(de)電(dian)(dian)(dian)(dian)容量(liang)決定。T1的(de)(de)次級(ji)(ji)線圈L2作(zuo)為(wei)(wei)(wei)(wei)振(zhen)(zhen)蕩(dang)器(qi)(qi)(qi)(qi)的(de)(de)反(fan)饋(kui)(kui)線圈，其“C”端(duan)(duan)(duan)接振(zhen)(zhen)蕩(dang)管(guan)(guan)(guan)VT1的(de)(de)基極(ji)(ji)，“D”端(duan)(duan)(duan)接VD2。由(you)于(yu)VD2處于(yu)正向(xiang)導(dao)通(tong)狀態，對高(gao)(gao)頻(pin)(pin)(pin)信號來說，“D”端(duan)(duan)(duan)可(ke)視(shi)為(wei)(wei)(wei)(wei)接地。在(zai)高(gao)(gao)頻(pin)(pin)(pin)變壓器(qi)(qi)(qi)(qi)T1中(zhong)，如果“A” 和(he)(he)“D”端(duan)(duan)(duan)分別為(wei)(wei)(wei)(wei)初、次級(ji)(ji)線圈繞線方向(xiang)的(de)(de)首端(duan)(duan)(duan)，則從“C”端(duan)(duan)(duan)輸入(ru)到(dao)振(zhen)(zhen)蕩(dang)管(guan)(guan)(guan)VT1基極(ji)(ji)的(de)(de)反(fan)饋(kui)(kui)信號，能夠(gou)使(shi)電(dian)(dian)(dian)(dian)路(lu)形成(cheng)正反(fan)饋(kui)(kui)而產生自激高(gao)(gao)頻(pin)(pin)(pin)振(zhen)(zhen)蕩(dang)。振(zhen)(zhen)蕩(dang)器(qi)(qi)(qi)(qi)反(fan)饋(kui)(kui)電(dian)(dian)(dian)(dian)壓的(de)(de)大(da)(da)小與(yu)線圈L1、L2的(de)(de)匝(za)數比(bi)有關，匝(za)數比(bi)過小，由(you)于(yu)反(fan)饋(kui)(kui)太弱，不容易起振(zhen)(zhen)，過大(da)(da)引起振(zhen)(zhen)蕩(dang)波形失(shi)真，還會使(shi)手持(chi)(chi)金屬(shu)探測器(qi)(qi)(qi)(qi)靈敏(min)度大(da)(da)為(wei)(wei)(wei)(wei)降低。振(zhen)(zhen)蕩(dang)管(guan)(guan)(guan)VT1的(de)(de)偏(pian)(pian)置電(dian)(dian)(dian)(dian)路(lu)由(you)R2和(he)(he)二極(ji)(ji)管(guan)(guan)(guan)VD2組成(cheng)，R2為(wei)(wei)(wei)(wei)VD2的(de)(de)限(xian)流電(dian)(dian)(dian)(dian)阻。由(you)于(yu)二極(ji)(ji)管(guan)(guan)(guan)正向(xiang)閾值電(dian)(dian)(dian)(dian)壓恒定（約(yue)0.7V），通(tong)過次級(ji)(ji)線圈L2加(jia)到(dao)VT1的(de)(de)基極(ji)(ji)，以得到(dao)穩(wen)(wen)定的(de)(de)偏(pian)(pian)置電(dian)(dian)(dian)(dian)壓。顯然(ran)，這(zhe)種穩(wen)(wen)壓式(shi)的(de)(de)偏(pian)(pian)置電(dian)(dian)(dian)(dian)路(lu)能夠(gou)大(da)(da)大(da)(da)增強VT1高(gao)(gao)頻(pin)(pin)(pin)振(zhen)(zhen)蕩(dang)器(qi)(qi)(qi)(qi)的(de)(de)穩(wen)(wen)定性。為(wei)(wei)(wei)(wei)了進(jin)一(yi)步(bu)提高(gao)(gao)手持(chi)(chi)金屬(shu)探測器(qi)(qi)(qi)(qi)的(de)(de)可(ke)靠(kao)性和(he)(he)靈敏(min)度，高(gao)(gao)頻(pin)(pin)(pin)振(zhen)(zhen)蕩(dang)器(qi)(qi)(qi)(qi)通(tong)過穩(wen)(wen)壓電(dian)(dian)(dian)(dian)路(lu)供電(dian)(dian)(dian)(dian)，其電(dian)(dian)(dian)(dian)路(lu)由(you)穩(wen)(wen)壓二極(ji)(ji)管(guan)(guan)(guan)VD1、限(xian)流電(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)(qi)R6和(he)(he)去(qu)耦電(dian)(dian)(dian)(dian)容器(qi)(qi)(qi)(qi)C5組成(cheng)。振(zhen)(zhen)蕩(dang)管(guan)(guan)(guan)VT1發射極(ji)(ji)與(yu)地之(zhi)間(jian)接有兩個串聯的(de)(de)電(dian)(dian)(dian)(dian)位器(qi)(qi)(qi)(qi)，具有發射極(ji)(ji)電(dian)(dian)(dian)(dian)流負(fu)反(fan)饋(kui)(kui)作(zuo)用(yong)，其電(dian)(dian)(dian)(dian)阻值越(yue)(yue)大(da)(da)，負(fu)反(fan)饋(kui)(kui)作(zuo)用(yong)越(yue)(yue)強，VT1的(de)(de)放大(da)(da)能力也就越(yue)(yue)低，甚至于(yu)使(shi)電(dian)(dian)(dian)(dian)路(lu)停振(zhen)(zhen)。RP1為(wei)(wei)(wei)(wei)振(zhen)(zhen)蕩(dang)器(qi)(qi)(qi)(qi)增益(yi)的(de)(de)粗調(diao)電(dian)(dian)(dian)(dian)位器(qi)(qi)(qi)(qi)，RP2為(wei)(wei)(wei)(wei)細(xi)調(diao)電(dian)(dian)(dian)(dian)位器(qi)(qi)(qi)(qi)。
2、振蕩檢測器
振(zhen)(zhen)蕩(dang)檢測(ce)器(qi)由三極(ji)管開(kai)(kai)關電(dian)(dian)(dian)(dian)路和(he)濾波(bo)電(dian)(dian)(dian)(dian)路組成(cheng)(cheng)。開(kai)(kai)關電(dian)(dian)(dian)(dian)路由三極(ji)管VT2、二(er)極(ji)管 VD2等(deng)組成(cheng)(cheng)，濾波(bo)電(dian)(dian)(dian)(dian)路由濾波(bo)電(dian)(dian)(dian)(dian)阻(zu)器(qi)R3，濾波(bo)電(dian)(dian)(dian)(dian)容器(qi)C2、C3和(he)C4組成(cheng)(cheng)。在(zai)開(kai)(kai)關電(dian)(dian)(dian)(dian)路中，VT2的基極(ji)與(yu)次級線圈L2的“C”端相連，當高頻(pin)(pin)振(zhen)(zhen)蕩(dang)器(qi)工作時(shi)(shi)，經(jing)高頻(pin)(pin)變壓器(qi)T1耦合過來的振(zhen)(zhen)蕩(dang)信(xin)號(hao)(hao)，正半周使(shi)VT2導通，VT2集電(dian)(dian)(dian)(dian)極(ji)輸(shu)出負(fu)脈(mo)沖信(xin)號(hao)(hao)，經(jing)過π型RC濾波(bo)器(qi)，在(zai)負(fu)載(zai)電(dian)(dian)(dian)(dian)阻(zu)器(qi)R4上(shang)輸(shu)出低(di)電(dian)(dian)(dian)(dian)平(ping)信(xin)號(hao)(hao)。當高頻(pin)(pin)振(zhen)(zhen)蕩(dang)器(qi)停振(zhen)(zhen)蕩(dang)時(shi)(shi)，“C”端無振(zhen)(zhen)蕩(dang)信(xin)號(hao)(hao)，又由于二(er)極(ji)管VD2接(jie)在(zai)VT2發射極(ji)與(yu)地之間，VT2基極(ji)被反(fan)向(xiang)偏(pian)置，VT2處于可靠的截止(zhi)狀態，VT2集電(dian)(dian)(dian)(dian)極(ji)為高電(dian)(dian)(dian)(dian)平(ping)，經(jing)過濾波(bo)器(qi)，在(zai)R4上(shang)得到高電(dian)(dian)(dian)(dian)平(ping)信(xin)號(hao)(hao)。由此(ci)可見，當高頻(pin)(pin)振(zhen)(zhen)蕩(dang)器(qi)正常工作時(shi)(shi)，在(zai)R4上(shang)得到低(di)電(dian)(dian)(dian)(dian)平(ping)信(xin)號(hao)(hao)，停振(zhen)(zhen)時(shi)(shi)，為高電(dian)(dian)(dian)(dian)平(ping)，由此(ci)完成(cheng)(cheng)了(le)對(dui)振(zhen)(zhen)蕩(dang)器(qi)工作狀態的檢測(ce)。
3、音頻振蕩器
音(yin)頻(pin)振蕩(dang)器(qi)采用互補型(xing)多諧振蕩(dang)器(qi)，由三極(ji)管VT3、VT4，電(dian)(dian)(dian)(dian)阻(zu)器(qi)R5、R7、 R8和電(dian)(dian)(dian)(dian)容器(qi)C6組(zu)成(cheng)。互補型(xing)多諧振蕩(dang)器(qi)采用兩只不(bu)同類型(xing)的三極(ji)管，其(qi)中VT3為NPN型(xing)三極(ji)管，VT4為PNP型(xing)三極(ji)管，連(lian)接成(cheng)互補的、能(neng)(neng)夠強化正(zheng)反饋(kui)的電(dian)(dian)(dian)(dian)路。在電(dian)(dian)(dian)(dian)路工(gong)作時，它們能(neng)(neng)夠交(jiao)替地進入導(dao)通和截止狀態，產生音(yin)頻(pin)振蕩(dang)。R7既是(shi)VT3負載(zai)電(dian)(dian)(dian)(dian)阻(zu)器(qi)，又是(shi)VT3導(dao)通時VT4基極(ji)限流電(dian)(dian)(dian)(dian)阻(zu)器(qi)。R8是(shi) VT4集(ji)電(dian)(dian)(dian)(dian)極(ji)負載(zai)電(dian)(dian)(dian)(dian)阻(zu)器(qi)，振蕩(dang)脈沖信(xin)號由VT4集(ji)電(dian)(dian)(dian)(dian)極(ji)輸出。R5和C6等是(shi)反饋(kui)電(dian)(dian)(dian)(dian)阻(zu)器(qi)和電(dian)(dian)(dian)(dian)容器(qi)，其(qi)數值大小(xiao)影響振蕩(dang)頻(pin)率的高低(di)。
4、功率放大器
功率放大器由三極管VT5、揚聲器BL等組成。從(cong)多(duo)諧(xie)振蕩器輸(shu)(shu)出(chu)的(de)正脈沖(chong)音頻信(xin)號(hao)經限流電阻器R9輸(shu)(shu)入到VT5的(de)基極，使(shi)其導通，在(zai)BL產生瞬時(shi)較強的(de)電流，驅(qu)動揚聲器發聲。由于VT5處于開關工作狀態，而導通時(shi)間又非常短，因此功率放大器非常省電，可以(yi)利用9V積層電池供電。
二、手持式金屬探測器原理是什么
了解了手持金(jin)屬探測(ce)器的(de)結構，接下來就可以介紹金(jin)屬探測(ce)器的(de)工作(zuo)原(yuan)理了：
手持金屬探測器利(li)(li)用電(dian)磁(ci)感(gan)應(ying)的(de)(de)原理，利(li)(li)用有交流電(dian)通過的(de)(de)線圈，產生迅(xun)速變化的(de)(de)磁(ci)場(chang)(chang)。這個磁(ci)場(chang)(chang)能在金屬物(wu)體內部能感(gan)生渦電(dian)流。渦電(dian)流又會產生磁(ci)場(chang)(chang)，倒過來影響原來的(de)(de)磁(ci)場(chang)(chang)，引發(fa)探測器發(fa)出鳴(ming)聲。
工(gong)作(zuo)時(shi)，其內部探測器(qi)會發出某一頻(pin)率的(de)電磁波，由于金屬有自感(gan)，會使(shi)這一頻(pin)率發生偏(pian)移，當(dang)它(ta)再(zai)接(jie)收到有偏(pian)差的(de)電磁波時(shi)，就把差頻(pin)放大，發出信號報警。
