手(shou)持式金屬(shu)探測器被設計用(yong)來探測人或(huo)物體攜帶的(de)金屬(shu)物，廣泛應用(yong)于安全檢查、考古、探礦等方面。手(shou)持金屬(shu)探測器的(de)結構主要由四部分組成：

1、高頻振蕩器

由三極(ji)管VT1和(he)高頻變壓器T1等(deng)組(zu)成，是一(yi)種變壓器反(fan)饋型(xing)LC振蕩器。

2、振(zhen)蕩檢測(ce)器

振(zhen)蕩(dang)(dang)檢測(ce)器(qi)(qi)(qi)由(you)三(san)極(ji)管(guan)開(kai)(kai)關電(dian)(dian)(dian)(dian)(dian)(dian)路和(he)濾波(bo)電(dian)(dian)(dian)(dian)(dian)(dian)路組(zu)成(cheng)。開(kai)(kai)關電(dian)(dian)(dian)(dian)(dian)(dian)路由(you)三(san)極(ji)管(guan)VT2、二極(ji)管(guan)VD2等組(zu)成(cheng)，濾波(bo)電(dian)(dian)(dian)(dian)(dian)(dian)路由(you)濾波(bo)電(dian)(dian)(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)R3，濾波(bo)電(dian)(dian)(dian)(dian)(dian)(dian)容器(qi)(qi)(qi)C2、C3和(he)C4組(zu)成(cheng)。在(zai)(zai)開(kai)(kai)關電(dian)(dian)(dian)(dian)(dian)(dian)路中，VT2的(de)(de)基(ji)極(ji)與(yu)次級線圈L2的(de)(de)“C”端(duan)相連，當高(gao)頻(pin)振(zhen)蕩(dang)(dang)器(qi)(qi)(qi)工(gong)作(zuo)時(shi)，經高(gao)頻(pin)變(bian)壓器(qi)(qi)(qi)T1耦合(he)過來的(de)(de)振(zhen)蕩(dang)(dang)信(xin)號(hao)(hao)，正半周使VT2導通，VT2集(ji)電(dian)(dian)(dian)(dian)(dian)(dian)極(ji)輸出(chu)負(fu)脈沖信(xin)號(hao)(hao)，經過π型RC濾波(bo)器(qi)(qi)(qi)，在(zai)(zai)負(fu)載(zai)電(dian)(dian)(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)R4上(shang)輸出(chu)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)信(xin)號(hao)(hao)。當高(gao)頻(pin)振(zhen)蕩(dang)(dang)器(qi)(qi)(qi)停(ting)振(zhen)蕩(dang)(dang)時(shi)，“C”端(duan)無振(zhen)蕩(dang)(dang)信(xin)號(hao)(hao)，又由(you)于二極(ji)管(guan)VD2接在(zai)(zai)VT2發射極(ji)與(yu)地之間，VT2基(ji)極(ji)被(bei)反向偏置(zhi)，VT2處于可靠的(de)(de)截(jie)止狀(zhuang)態(tai)，VT2集(ji)電(dian)(dian)(dian)(dian)(dian)(dian)極(ji)為高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)，經過濾波(bo)器(qi)(qi)(qi)，在(zai)(zai)R4上(shang)得到(dao)高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)信(xin)號(hao)(hao)。由(you)此可見，當高(gao)頻(pin)振(zhen)蕩(dang)(dang)器(qi)(qi)(qi)正常工(gong)作(zuo)時(shi)，在(zai)(zai)R4上(shang)得到(dao)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)信(xin)號(hao)(hao)，停(ting)振(zhen)時(shi)，為高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)平(ping)，由(you)此完成(cheng)了對振(zhen)蕩(dang)(dang)器(qi)(qi)(qi)工(gong)作(zuo)狀(zhuang)態(tai)的(de)(de)檢測(ce)。

3、音頻振蕩器

音(yin)頻振(zhen)蕩(dang)(dang)器(qi)(qi)(qi)采(cai)用互(hu)補(bu)型(xing)多諧振(zhen)蕩(dang)(dang)器(qi)(qi)(qi)，由三極管(guan)VT3、VT4，電(dian)(dian)阻器(qi)(qi)(qi)R5、R7、R8和(he)電(dian)(dian)容器(qi)(qi)(qi)C6組成(cheng)。互(hu)補(bu)型(xing)多諧振(zhen)蕩(dang)(dang)器(qi)(qi)(qi)采(cai)用兩(liang)只(zhi)不同(tong)類型(xing)的(de)三極管(guan)，其(qi)中VT3為NPN型(xing)三極管(guan)，VT4為PNP型(xing)三極管(guan)，連接成(cheng)互(hu)補(bu)的(de)、能夠強(qiang)化正反饋的(de)電(dian)(dian)路(lu)。在電(dian)(dian)路(lu)工作時，它們(men)能夠交替地進(jin)入導(dao)通(tong)和(he)截止狀態，產生音(yin)頻振(zhen)蕩(dang)(dang)。R7既是VT3負(fu)載電(dian)(dian)阻器(qi)(qi)(qi)，又是VT3導(dao)通(tong)時VT4基(ji)極限流電(dian)(dian)阻器(qi)(qi)(qi)。R8是 VT4集電(dian)(dian)極負(fu)載電(dian)(dian)阻器(qi)(qi)(qi)，振(zhen)蕩(dang)(dang)脈沖信號(hao)由VT4集電(dian)(dian)極輸出。R5和(he)C6等是反饋電(dian)(dian)阻器(qi)(qi)(qi)和(he)電(dian)(dian)容器(qi)(qi)(qi)，其(qi)數值(zhi)大小(xiao)影響振(zhen)蕩(dang)(dang)頻率的(de)高低。

4、功率放大器

功率放大器由(you)三極管VT5、揚(yang)聲(sheng)器BL等組成。從多諧振蕩器輸出的正(zheng)脈沖音(yin)頻信號經限流(liu)電(dian)阻器R9輸入到VT5的基極，使其導通，在BL產生(sheng)瞬(shun)時較(jiao)強的電(dian)流(liu)，驅(qu)動揚(yang)聲(sheng)器發聲(sheng)。由(you)于VT5處于開關工(gong)作狀(zhuang)態(tai)，而導通時間又非常短，因此功率放大器非常省電(dian)，可以利用9V積層(ceng)電(dian)池供電(dian)。