手持式金(jin)屬探(tan)測器被設計用來探(tan)測人或物(wu)體攜(xie)帶的(de)金(jin)屬物(wu)，廣泛應用于安(an)全檢查(cha)、考古、探(tan)礦等(deng)方面。手持金(jin)屬探(tan)測器的(de)結構(gou)主要由(you)四部(bu)分組(zu)成：

1、高頻振蕩器

由三極(ji)管VT1和高頻變壓(ya)器T1等組(zu)成，是一(yi)種變壓(ya)器反(fan)饋型LC振蕩器。

2、振蕩檢測器

振(zhen)蕩(dang)(dang)(dang)檢測器(qi)(qi)(qi)(qi)(qi)由(you)(you)三極管(guan)開關電(dian)(dian)(dian)路(lu)(lu)和濾波(bo)(bo)電(dian)(dian)(dian)路(lu)(lu)組(zu)成。開關電(dian)(dian)(dian)路(lu)(lu)由(you)(you)三極管(guan)VT2、二(er)極管(guan)VD2等組(zu)成，濾波(bo)(bo)電(dian)(dian)(dian)路(lu)(lu)由(you)(you)濾波(bo)(bo)電(dian)(dian)(dian)阻器(qi)(qi)(qi)(qi)(qi)R3，濾波(bo)(bo)電(dian)(dian)(dian)容器(qi)(qi)(qi)(qi)(qi)C2、C3和C4組(zu)成。在開關電(dian)(dian)(dian)路(lu)(lu)中，VT2的基極與次級線圈L2的“C”端(duan)相連(lian)，當高(gao)頻(pin)(pin)振(zhen)蕩(dang)(dang)(dang)器(qi)(qi)(qi)(qi)(qi)工作(zuo)時，經高(gao)頻(pin)(pin)變壓(ya)器(qi)(qi)(qi)(qi)(qi)T1耦合(he)過來的振(zhen)蕩(dang)(dang)(dang)信(xin)號(hao)(hao)，正半周(zhou)使VT2導通，VT2集(ji)電(dian)(dian)(dian)極輸出負(fu)脈沖信(xin)號(hao)(hao)，經過π型RC濾波(bo)(bo)器(qi)(qi)(qi)(qi)(qi)，在負(fu)載電(dian)(dian)(dian)阻器(qi)(qi)(qi)(qi)(qi)R4上(shang)(shang)輸出低電(dian)(dian)(dian)平(ping)信(xin)號(hao)(hao)。當高(gao)頻(pin)(pin)振(zhen)蕩(dang)(dang)(dang)器(qi)(qi)(qi)(qi)(qi)停(ting)振(zhen)蕩(dang)(dang)(dang)時，“C”端(duan)無振(zhen)蕩(dang)(dang)(dang)信(xin)號(hao)(hao)，又(you)由(you)(you)于(yu)二(er)極管(guan)VD2接在VT2發射極與地之間，VT2基極被反(fan)向偏(pian)置，VT2處于(yu)可靠的截止狀(zhuang)態，VT2集(ji)電(dian)(dian)(dian)極為高(gao)電(dian)(dian)(dian)平(ping)，經過濾波(bo)(bo)器(qi)(qi)(qi)(qi)(qi)，在R4上(shang)(shang)得到高(gao)電(dian)(dian)(dian)平(ping)信(xin)號(hao)(hao)。由(you)(you)此可見，當高(gao)頻(pin)(pin)振(zhen)蕩(dang)(dang)(dang)器(qi)(qi)(qi)(qi)(qi)正常工作(zuo)時，在R4上(shang)(shang)得到低電(dian)(dian)(dian)平(ping)信(xin)號(hao)(hao)，停(ting)振(zhen)時，為高(gao)電(dian)(dian)(dian)平(ping)，由(you)(you)此完成了對振(zhen)蕩(dang)(dang)(dang)器(qi)(qi)(qi)(qi)(qi)工作(zuo)狀(zhuang)態的檢測。

3、音頻振蕩器

音頻振(zhen)蕩(dang)器(qi)采(cai)用互補(bu)型(xing)多諧振(zhen)蕩(dang)器(qi)，由三極管VT3、VT4，電(dian)(dian)阻(zu)器(qi)R5、R7、R8和電(dian)(dian)容(rong)(rong)器(qi)C6組成。互補(bu)型(xing)多諧振(zhen)蕩(dang)器(qi)采(cai)用兩只不(bu)同類型(xing)的(de)(de)三極管，其中(zhong)VT3為(wei)NPN型(xing)三極管，VT4為(wei)PNP型(xing)三極管，連接成互補(bu)的(de)(de)、能夠強(qiang)化正反(fan)饋的(de)(de)電(dian)(dian)路(lu)。在電(dian)(dian)路(lu)工作時，它(ta)們能夠交(jiao)替地進入(ru)導(dao)通和截止狀(zhuang)態，產生音頻振(zhen)蕩(dang)。R7既是VT3負載電(dian)(dian)阻(zu)器(qi)，又是VT3導(dao)通時VT4基極限流電(dian)(dian)阻(zu)器(qi)。R8是 VT4集電(dian)(dian)極負載電(dian)(dian)阻(zu)器(qi)，振(zhen)蕩(dang)脈沖信(xin)號由VT4集電(dian)(dian)極輸出。R5和C6等是反(fan)饋電(dian)(dian)阻(zu)器(qi)和電(dian)(dian)容(rong)(rong)器(qi)，其數值大小影(ying)響振(zhen)蕩(dang)頻率的(de)(de)高低。

4、功率放大器

功率放(fang)大器(qi)(qi)(qi)由(you)三極(ji)管VT5、揚聲器(qi)(qi)(qi)BL等(deng)組(zu)成。從多諧(xie)振蕩器(qi)(qi)(qi)輸(shu)出的正(zheng)脈沖音頻信號經限流(liu)電(dian)阻器(qi)(qi)(qi)R9輸(shu)入到(dao)VT5的基極(ji)，使其導通(tong)，在BL產生瞬(shun)時較強(qiang)的電(dian)流(liu)，驅動揚聲器(qi)(qi)(qi)發聲。由(you)于(yu)VT5處于(yu)開關工(gong)作狀態，而導通(tong)時間(jian)又非常(chang)(chang)短，因此(ci)功率放(fang)大器(qi)(qi)(qi)非常(chang)(chang)省電(dian)，可以利用(yong)9V積(ji)層電(dian)池(chi)供電(dian)。