手持式金(jin)屬(shu)探測(ce)器(qi)被設計用來探測(ce)人(ren)或物(wu)體(ti)攜帶的(de)金(jin)屬(shu)物(wu)，廣(guang)泛應(ying)用于安全檢查、考(kao)古、探礦(kuang)等(deng)方(fang)面。手持金(jin)屬(shu)探測(ce)器(qi)的(de)結構主要由四部(bu)分(fen)組成：

1、高頻振蕩器

由三極管VT1和高頻(pin)變(bian)壓器(qi)T1等組(zu)成，是一種變(bian)壓器(qi)反饋型LC振蕩器(qi)。

2、振蕩(dang)檢測器

振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)(dang)檢測(ce)器(qi)(qi)(qi)(qi)由(you)三(san)極管開關電(dian)(dian)(dian)(dian)路(lu)和濾波電(dian)(dian)(dian)(dian)路(lu)組成(cheng)。開關電(dian)(dian)(dian)(dian)路(lu)由(you)三(san)極管VT2、二極管VD2等組成(cheng)，濾波電(dian)(dian)(dian)(dian)路(lu)由(you)濾波電(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)(qi)R3，濾波電(dian)(dian)(dian)(dian)容器(qi)(qi)(qi)(qi)C2、C3和C4組成(cheng)。在(zai)開關電(dian)(dian)(dian)(dian)路(lu)中，VT2的(de)基極與次(ci)級線(xian)圈L2的(de)“C”端相(xiang)連，當高(gao)頻(pin)振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)(dang)器(qi)(qi)(qi)(qi)工(gong)作(zuo)時(shi)(shi)，經(jing)高(gao)頻(pin)變壓器(qi)(qi)(qi)(qi)T1耦合過來(lai)的(de)振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)(dang)信(xin)號(hao)，正半周使VT2導通，VT2集電(dian)(dian)(dian)(dian)極輸出(chu)負(fu)脈(mo)沖(chong)信(xin)號(hao)，經(jing)過π型RC濾波器(qi)(qi)(qi)(qi)，在(zai)負(fu)載電(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)(qi)R4上輸出(chu)低電(dian)(dian)(dian)(dian)平(ping)信(xin)號(hao)。當高(gao)頻(pin)振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)(dang)器(qi)(qi)(qi)(qi)停振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)(dang)時(shi)(shi)，“C”端無振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)(dang)信(xin)號(hao)，又由(you)于二極管VD2接在(zai)VT2發射極與地(di)之間，VT2基極被(bei)反向偏置，VT2處(chu)于可靠的(de)截止狀(zhuang)態，VT2集電(dian)(dian)(dian)(dian)極為高(gao)電(dian)(dian)(dian)(dian)平(ping)，經(jing)過濾波器(qi)(qi)(qi)(qi)，在(zai)R4上得到高(gao)電(dian)(dian)(dian)(dian)平(ping)信(xin)號(hao)。由(you)此可見，當高(gao)頻(pin)振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)(dang)器(qi)(qi)(qi)(qi)正常工(gong)作(zuo)時(shi)(shi)，在(zai)R4上得到低電(dian)(dian)(dian)(dian)平(ping)信(xin)號(hao)，停振(zhen)(zhen)(zhen)時(shi)(shi)，為高(gao)電(dian)(dian)(dian)(dian)平(ping)，由(you)此完成(cheng)了對振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)(dang)器(qi)(qi)(qi)(qi)工(gong)作(zuo)狀(zhuang)態的(de)檢測(ce)。

3、音頻振蕩器

音(yin)頻振蕩(dang)器(qi)(qi)采(cai)用互補型(xing)多(duo)諧振蕩(dang)器(qi)(qi)，由三(san)(san)(san)極(ji)管VT3、VT4，電(dian)阻(zu)器(qi)(qi)R5、R7、R8和電(dian)容器(qi)(qi)C6組成(cheng)。互補型(xing)多(duo)諧振蕩(dang)器(qi)(qi)采(cai)用兩只(zhi)不(bu)同類型(xing)的三(san)(san)(san)極(ji)管，其中VT3為NPN型(xing)三(san)(san)(san)極(ji)管，VT4為PNP型(xing)三(san)(san)(san)極(ji)管，連接成(cheng)互補的、能(neng)夠強化(hua)正反饋的電(dian)路。在電(dian)路工作時(shi)，它們能(neng)夠交(jiao)替(ti)地進入導(dao)通(tong)和截止狀態，產(chan)生音(yin)頻振蕩(dang)。R7既(ji)是VT3負(fu)載電(dian)阻(zu)器(qi)(qi)，又是VT3導(dao)通(tong)時(shi)VT4基(ji)極(ji)限流電(dian)阻(zu)器(qi)(qi)。R8是 VT4集(ji)電(dian)極(ji)負(fu)載電(dian)阻(zu)器(qi)(qi)，振蕩(dang)脈沖信號(hao)由VT4集(ji)電(dian)極(ji)輸(shu)出。R5和C6等(deng)是反饋電(dian)阻(zu)器(qi)(qi)和電(dian)容器(qi)(qi)，其數值大小影響振蕩(dang)頻率的高低。

4、功率放大器

功率放大(da)器(qi)由三極(ji)管VT5、揚聲器(qi)BL等(deng)組成。從多諧振蕩器(qi)輸出的正脈沖音頻信(xin)號經限流電阻器(qi)R9輸入到VT5的基極(ji)，使(shi)其導(dao)通，在(zai)BL產(chan)生瞬時較強的電流，驅動(dong)揚聲器(qi)發聲。由于VT5處于開關工作(zuo)狀態，而導(dao)通時間又非常短，因此功率放大(da)器(qi)非常省電，可以利(li)用9V積層電池供電。