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(you)四部(bu)分組成(cheng)：
1、高頻振蕩器
由三極(ji)(ji)(ji)管(guan)VT1和(he)(he)高(gao)(gao)頻(pin)(pin)(pin)變(bian)壓(ya)(ya)器(qi)(qi)(qi)(qi)(qi)T1等(deng)組(zu)(zu)成(cheng)，是(shi)一(yi)種變(bian)壓(ya)(ya)器(qi)(qi)(qi)(qi)(qi)反(fan)(fan)(fan)(fan)饋(kui)(kui)型LC振(zhen)(zhen)蕩(dang)器(qi)(qi)(qi)(qi)(qi)。T1的(de)(de)(de)(de)(de)(de)初(chu)級(ji)(ji)線(xian)圈L1和(he)(he)電(dian)(dian)(dian)(dian)容器(qi)(qi)(qi)(qi)(qi)C1組(zu)(zu)成(cheng)LC并聯(lian)振(zhen)(zhen)蕩(dang)回路(lu)(lu)(lu)，其振(zhen)(zhen)蕩(dang)頻(pin)(pin)(pin)率約200kHz，由L1的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)感量和(he)(he)C1的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)容量決定(ding)。T1的(de)(de)(de)(de)(de)(de)次級(ji)(ji)線(xian)圈L2作為(wei)(wei)(wei)(wei)振(zhen)(zhen)蕩(dang)器(qi)(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)反(fan)(fan)(fan)(fan)饋(kui)(kui)線(xian)圈，其“C”端(duan)(duan)(duan)接(jie)振(zhen)(zhen)蕩(dang)管(guan)VT1的(de)(de)(de)(de)(de)(de)基(ji)極(ji)(ji)(ji)，“D”端(duan)(duan)(duan)接(jie)VD2。由于VD2處于正向(xiang)導(dao)通(tong)狀(zhuang)態，對(dui)高(gao)(gao)頻(pin)(pin)(pin)信(xin)號來說，“D”端(duan)(duan)(duan)可(ke)視為(wei)(wei)(wei)(wei)接(jie)地。在高(gao)(gao)頻(pin)(pin)(pin)變(bian)壓(ya)(ya)器(qi)(qi)(qi)(qi)(qi)T1中，如果“A” 和(he)(he)“D”端(duan)(duan)(duan)分別為(wei)(wei)(wei)(wei)初(chu)、次級(ji)(ji)線(xian)圈繞線(xian)方向(xiang)的(de)(de)(de)(de)(de)(de)首端(duan)(duan)(duan)，則從(cong)“C”端(duan)(duan)(duan)輸入到振(zhen)(zhen)蕩(dang)管(guan)VT1基(ji)極(ji)(ji)(ji)的(de)(de)(de)(de)(de)(de)反(fan)(fan)(fan)(fan)饋(kui)(kui)信(xin)號，能(neng)夠使電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)形成(cheng)正反(fan)(fan)(fan)(fan)饋(kui)(kui)而產生自(zi)激高(gao)(gao)頻(pin)(pin)(pin)振(zhen)(zhen)蕩(dang)。振(zhen)(zhen)蕩(dang)器(qi)(qi)(qi)(qi)(qi)反(fan)(fan)(fan)(fan)饋(kui)(kui)電(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)(de)(de)(de)(de)(de)大小(xiao)與線(xian)圈L1、L2的(de)(de)(de)(de)(de)(de)匝數(shu)比(bi)有(you)關，匝數(shu)比(bi)過小(xiao)，由于反(fan)(fan)(fan)(fan)饋(kui)(kui)太弱，不容易起(qi)振(zhen)(zhen)，過大引起(qi)振(zhen)(zhen)蕩(dang)波(bo)形失真，還會使手持金屬探測器(qi)(qi)(qi)(qi)(qi)靈(ling)敏(min)度大為(wei)(wei)(wei)(wei)降(jiang)低。振(zhen)(zhen)蕩(dang)管(guan)VT1的(de)(de)(de)(de)(de)(de)偏(pian)置(zhi)電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)由R2和(he)(he)二極(ji)(ji)(ji)管(guan)VD2組(zu)(zu)成(cheng)，R2為(wei)(wei)(wei)(wei)VD2的(de)(de)(de)(de)(de)(de)限(xian)(xian)流電(dian)(dian)(dian)(dian)阻。由于二極(ji)(ji)(ji)管(guan)正向(xiang)閾值電(dian)(dian)(dian)(dian)壓(ya)(ya)恒定(ding)（約0.7V），通(tong)過次級(ji)(ji)線(xian)圈L2加到VT1的(de)(de)(de)(de)(de)(de)基(ji)極(ji)(ji)(ji)，以得到穩定(ding)的(de)(de)(de)(de)(de)(de)偏(pian)置(zhi)電(dian)(dian)(dian)(dian)壓(ya)(ya)。顯然，這種穩壓(ya)(ya)式的(de)(de)(de)(de)(de)(de)偏(pian)置(zhi)電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)能(neng)夠大大增強(qiang)VT1高(gao)(gao)頻(pin)(pin)(pin)振(zhen)(zhen)蕩(dang)器(qi)(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)穩定(ding)性。為(wei)(wei)(wei)(wei)了(le)進一(yi)步提高(gao)(gao)手持金屬探測器(qi)(qi)(qi)(qi)(qi)的(de)(de)(de)(de)(de)(de)可(ke)靠性和(he)(he)靈(ling)敏(min)度，高(gao)(gao)頻(pin)(pin)(pin)振(zhen)(zhen)蕩(dang)器(qi)(qi)(qi)(qi)(qi)通(tong)過穩壓(ya)(ya)電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)供電(dian)(dian)(dian)(dian)，其電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)由穩壓(ya)(ya)二極(ji)(ji)(ji)管(guan)VD1、限(xian)(xian)流電(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)(qi)(qi)R6和(he)(he)去耦(ou)電(dian)(dian)(dian)(dian)容器(qi)(qi)(qi)(qi)(qi)C5組(zu)(zu)成(cheng)。振(zhen)(zhen)蕩(dang)管(guan)VT1發射極(ji)(ji)(ji)與地之間接(jie)有(you)兩個串聯(lian)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)位器(qi)(qi)(qi)(qi)(qi)，具有(you)發射極(ji)(ji)(ji)電(dian)(dian)(dian)(dian)流負反(fan)(fan)(fan)(fan)饋(kui)(kui)作用，其電(dian)(dian)(dian)(dian)阻值越(yue)(yue)大，負反(fan)(fan)(fan)(fan)饋(kui)(kui)作用越(yue)(yue)強(qiang)，VT1的(de)(de)(de)(de)(de)(de)放大能(neng)力也就(jiu)越(yue)(yue)低，甚至于使電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)停(ting)振(zhen)(zhen)。RP1為(wei)(wei)(wei)(wei)振(zhen)(zhen)蕩(dang)器(qi)(qi)(qi)(qi)(qi)增益(yi)的(de)(de)(de)(de)(de)(de)粗調電(dian)(dian)(dian)(dian)位器(qi)(qi)(qi)(qi)(qi)，RP2為(wei)(wei)(wei)(wei)細調電(dian)(dian)(dian)(dian)位器(qi)(qi)(qi)(qi)(qi)。
2、振蕩檢測器
振(zhen)蕩(dang)檢測器(qi)(qi)由(you)(you)三(san)極(ji)(ji)(ji)管(guan)開(kai)關電(dian)(dian)(dian)(dian)(dian)路和(he)濾(lv)(lv)波電(dian)(dian)(dian)(dian)(dian)路組成(cheng)。開(kai)關電(dian)(dian)(dian)(dian)(dian)路由(you)(you)三(san)極(ji)(ji)(ji)管(guan)VT2、二極(ji)(ji)(ji)管(guan) VD2等組成(cheng)，濾(lv)(lv)波電(dian)(dian)(dian)(dian)(dian)路由(you)(you)濾(lv)(lv)波電(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)器(qi)(qi)R3，濾(lv)(lv)波電(dian)(dian)(dian)(dian)(dian)容器(qi)(qi)C2、C3和(he)C4組成(cheng)。在開(kai)關電(dian)(dian)(dian)(dian)(dian)路中，VT2的基極(ji)(ji)(ji)與次級(ji)線圈L2的“C”端相連，當高頻振(zhen)蕩(dang)器(qi)(qi)工作時，經高頻變壓(ya)器(qi)(qi)T1耦(ou)合過來(lai)的振(zhen)蕩(dang)信(xin)(xin)號(hao)，正半周使(shi)VT2導(dao)通，VT2集電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)輸出負脈沖信(xin)(xin)號(hao)，經過π型RC濾(lv)(lv)波器(qi)(qi)，在負載電(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)器(qi)(qi)R4上(shang)(shang)輸出低電(dian)(dian)(dian)(dian)(dian)平(ping)(ping)信(xin)(xin)號(hao)。當高頻振(zhen)蕩(dang)器(qi)(qi)停振(zhen)蕩(dang)時，“C”端無振(zhen)蕩(dang)信(xin)(xin)號(hao)，又(you)由(you)(you)于二極(ji)(ji)(ji)管(guan)VD2接在VT2發射(she)極(ji)(ji)(ji)與地之間，VT2基極(ji)(ji)(ji)被反向(xiang)偏置，VT2處于可靠(kao)的截(jie)止(zhi)狀態(tai)，VT2集電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)為(wei)高電(dian)(dian)(dian)(dian)(dian)平(ping)(ping)，經過濾(lv)(lv)波器(qi)(qi)，在R4上(shang)(shang)得到高電(dian)(dian)(dian)(dian)(dian)平(ping)(ping)信(xin)(xin)號(hao)。由(you)(you)此可見(jian)，當高頻振(zhen)蕩(dang)器(qi)(qi)正常(chang)工作時，在R4上(shang)(shang)得到低電(dian)(dian)(dian)(dian)(dian)平(ping)(ping)信(xin)(xin)號(hao)，停振(zhen)時，為(wei)高電(dian)(dian)(dian)(dian)(dian)平(ping)(ping)，由(you)(you)此完成(cheng)了對振(zhen)蕩(dang)器(qi)(qi)工作狀態(tai)的檢測。
3、音頻振蕩器
音頻(pin)振蕩器采用互補(bu)型多諧(xie)振蕩器，由三極(ji)(ji)管(guan)VT3、VT4，電(dian)阻器R5、R7、 R8和(he)電(dian)容器C6組(zu)成。互補(bu)型多諧(xie)振蕩器采用兩只(zhi)不同(tong)類型的三極(ji)(ji)管(guan)，其中VT3為NPN型三極(ji)(ji)管(guan)，VT4為PNP型三極(ji)(ji)管(guan)，連接成互補(bu)的、能(neng)夠強(qiang)化正反饋(kui)的電(dian)路。在(zai)電(dian)路工作時，它(ta)們能(neng)夠交替地進入(ru)導通和(he)截止狀態，產(chan)生音頻(pin)振蕩。R7既是VT3負載(zai)電(dian)阻器，又是VT3導通時VT4基極(ji)(ji)限(xian)流電(dian)阻器。R8是 VT4集電(dian)極(ji)(ji)負載(zai)電(dian)阻器，振蕩脈沖信號由VT4集電(dian)極(ji)(ji)輸出。R5和(he)C6等是反饋(kui)電(dian)阻器和(he)電(dian)容器，其數值(zhi)大小影響(xiang)振蕩頻(pin)率的高(gao)低。
4、功率放大器
功率(lv)放(fang)大器由三(san)極管(guan)VT5、揚聲器BL等組成。從多諧振蕩器輸(shu)出(chu)的(de)正(zheng)脈沖(chong)音頻信號經限流(liu)電阻器R9輸(shu)入到(dao)VT5的(de)基極，使其導通，在BL產(chan)生瞬時較強的(de)電流(liu)，驅(qu)動揚聲器發聲。由于(yu)VT5處(chu)于(yu)開關工作狀態，而導通時間又(you)非(fei)常(chang)短，因此功率(lv)放(fang)大器非(fei)常(chang)省電，可以利用9V積層電池供電。
二、手持式金屬探測器原理是什么
了(le)解了(le)手持(chi)金(jin)屬探測器(qi)的(de)結構，接下來就可以介紹金(jin)屬探測器(qi)的(de)工作原(yuan)理了(le)：
手持金屬探測器利用電(dian)磁(ci)(ci)感應的(de)原理，利用有交流電(dian)通過的(de)線圈，產生(sheng)(sheng)迅速變化(hua)的(de)磁(ci)(ci)場。這個(ge)磁(ci)(ci)場能(neng)在金(jin)屬物體內(nei)部能(neng)感生(sheng)(sheng)渦(wo)電(dian)流。渦(wo)電(dian)流又(you)會(hui)產生(sheng)(sheng)磁(ci)(ci)場，倒過來影響原來的(de)磁(ci)(ci)場，引發(fa)探測器發(fa)出鳴(ming)聲。
工作時，其內部探測器會發(fa)出某一頻率的(de)電磁(ci)(ci)波，由于金屬有自(zi)感(gan)，會使這(zhe)一頻率發(fa)生偏移，當它再接收到有偏差的(de)電磁(ci)(ci)波時，就把差頻放大，發(fa)出信號報警。
