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
由三極(ji)管(guan)(guan)VT1和(he)(he)高(gao)(gao)(gao)頻(pin)變(bian)壓(ya)器(qi)(qi)(qi)(qi)(qi)(qi)T1等組成，是一種變(bian)壓(ya)器(qi)(qi)(qi)(qi)(qi)(qi)反(fan)饋型LC振蕩(dang)(dang)器(qi)(qi)(qi)(qi)(qi)(qi)。T1的(de)(de)初(chu)級(ji)線(xian)圈(quan)(quan)L1和(he)(he)電(dian)(dian)(dian)(dian)容器(qi)(qi)(qi)(qi)(qi)(qi)C1組成LC并聯振蕩(dang)(dang)回路，其(qi)振蕩(dang)(dang)頻(pin)率約(yue)200kHz，由L1的(de)(de)電(dian)(dian)(dian)(dian)感(gan)量和(he)(he)C1的(de)(de)電(dian)(dian)(dian)(dian)容量決(jue)定(ding)(ding)。T1的(de)(de)次級(ji)線(xian)圈(quan)(quan)L2作(zuo)為(wei)振蕩(dang)(dang)器(qi)(qi)(qi)(qi)(qi)(qi)的(de)(de)反(fan)饋線(xian)圈(quan)(quan)，其(qi)“C”端(duan)接(jie)(jie)振蕩(dang)(dang)管(guan)(guan)VT1的(de)(de)基極(ji)，“D”端(duan)接(jie)(jie)VD2。由于VD2處于正向導通(tong)狀態，對高(gao)(gao)(gao)頻(pin)信號來(lai)說，“D”端(duan)可視為(wei)接(jie)(jie)地。在高(gao)(gao)(gao)頻(pin)變(bian)壓(ya)器(qi)(qi)(qi)(qi)(qi)(qi)T1中，如(ru)果“A” 和(he)(he)“D”端(duan)分別為(wei)初(chu)、次級(ji)線(xian)圈(quan)(quan)繞線(xian)方向的(de)(de)首端(duan)，則從“C”端(duan)輸(shu)入到振蕩(dang)(dang)管(guan)(guan)VT1基極(ji)的(de)(de)反(fan)饋信號，能夠(gou)使(shi)電(dian)(dian)(dian)(dian)路形(xing)成正反(fan)饋而產生自激(ji)高(gao)(gao)(gao)頻(pin)振蕩(dang)(dang)。振蕩(dang)(dang)器(qi)(qi)(qi)(qi)(qi)(qi)反(fan)饋電(dian)(dian)(dian)(dian)壓(ya)的(de)(de)大小與線(xian)圈(quan)(quan)L1、L2的(de)(de)匝數(shu)比(bi)有關(guan)，匝數(shu)比(bi)過小，由于反(fan)饋太弱，不容易起(qi)振，過大引起(qi)振蕩(dang)(dang)波形(xing)失真，還(huan)會使(shi)手持(chi)(chi)金屬探(tan)測器(qi)(qi)(qi)(qi)(qi)(qi)靈敏度(du)大為(wei)降低。振蕩(dang)(dang)管(guan)(guan)VT1的(de)(de)偏(pian)置(zhi)(zhi)電(dian)(dian)(dian)(dian)路由R2和(he)(he)二極(ji)管(guan)(guan)VD2組成，R2為(wei)VD2的(de)(de)限流電(dian)(dian)(dian)(dian)阻。由于二極(ji)管(guan)(guan)正向閾值電(dian)(dian)(dian)(dian)壓(ya)恒(heng)定(ding)(ding)（約(yue)0.7V），通(tong)過次級(ji)線(xian)圈(quan)(quan)L2加到VT1的(de)(de)基極(ji)，以得到穩定(ding)(ding)的(de)(de)偏(pian)置(zhi)(zhi)電(dian)(dian)(dian)(dian)壓(ya)。顯然，這種穩壓(ya)式的(de)(de)偏(pian)置(zhi)(zhi)電(dian)(dian)(dian)(dian)路能夠(gou)大大增(zeng)(zeng)強VT1高(gao)(gao)(gao)頻(pin)振蕩(dang)(dang)器(qi)(qi)(qi)(qi)(qi)(qi)的(de)(de)穩定(ding)(ding)性(xing)。為(wei)了(le)進一步提高(gao)(gao)(gao)手持(chi)(chi)金屬探(tan)測器(qi)(qi)(qi)(qi)(qi)(qi)的(de)(de)可靠性(xing)和(he)(he)靈敏度(du)，高(gao)(gao)(gao)頻(pin)振蕩(dang)(dang)器(qi)(qi)(qi)(qi)(qi)(qi)通(tong)過穩壓(ya)電(dian)(dian)(dian)(dian)路供電(dian)(dian)(dian)(dian)，其(qi)電(dian)(dian)(dian)(dian)路由穩壓(ya)二極(ji)管(guan)(guan)VD1、限流電(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)(qi)(qi)(qi)R6和(he)(he)去(qu)耦電(dian)(dian)(dian)(dian)容器(qi)(qi)(qi)(qi)(qi)(qi)C5組成。振蕩(dang)(dang)管(guan)(guan)VT1發(fa)射(she)(she)極(ji)與地之(zhi)間接(jie)(jie)有兩(liang)個串聯的(de)(de)電(dian)(dian)(dian)(dian)位(wei)(wei)器(qi)(qi)(qi)(qi)(qi)(qi)，具(ju)有發(fa)射(she)(she)極(ji)電(dian)(dian)(dian)(dian)流負反(fan)饋作(zuo)用(yong)，其(qi)電(dian)(dian)(dian)(dian)阻值越大，負反(fan)饋作(zuo)用(yong)越強，VT1的(de)(de)放(fang)大能力也就越低，甚至于使(shi)電(dian)(dian)(dian)(dian)路停振。RP1為(wei)振蕩(dang)(dang)器(qi)(qi)(qi)(qi)(qi)(qi)增(zeng)(zeng)益的(de)(de)粗調(diao)電(dian)(dian)(dian)(dian)位(wei)(wei)器(qi)(qi)(qi)(qi)(qi)(qi)，RP2為(wei)細調(diao)電(dian)(dian)(dian)(dian)位(wei)(wei)器(qi)(qi)(qi)(qi)(qi)(qi)。
2、振蕩檢測器
振(zhen)(zhen)蕩檢測(ce)器(qi)由(you)三極(ji)(ji)(ji)管開(kai)關電(dian)(dian)(dian)路(lu)和濾波電(dian)(dian)(dian)路(lu)組成(cheng)。開(kai)關電(dian)(dian)(dian)路(lu)由(you)三極(ji)(ji)(ji)管VT2、二(er)極(ji)(ji)(ji)管 VD2等組成(cheng)，濾波電(dian)(dian)(dian)路(lu)由(you)濾波電(dian)(dian)(dian)阻(zu)器(qi)R3，濾波電(dian)(dian)(dian)容器(qi)C2、C3和C4組成(cheng)。在開(kai)關電(dian)(dian)(dian)路(lu)中，VT2的(de)(de)基(ji)極(ji)(ji)(ji)與次級線圈(quan)L2的(de)(de)“C”端相連(lian)，當(dang)高(gao)頻振(zhen)(zhen)蕩器(qi)工(gong)作時(shi)，經(jing)高(gao)頻變(bian)壓器(qi)T1耦合(he)過(guo)(guo)來的(de)(de)振(zhen)(zhen)蕩信號(hao)(hao)，正半周使VT2導通，VT2集(ji)電(dian)(dian)(dian)極(ji)(ji)(ji)輸出(chu)(chu)負脈沖信號(hao)(hao)，經(jing)過(guo)(guo)π型RC濾波器(qi)，在負載電(dian)(dian)(dian)阻(zu)器(qi)R4上(shang)輸出(chu)(chu)低電(dian)(dian)(dian)平(ping)信號(hao)(hao)。當(dang)高(gao)頻振(zhen)(zhen)蕩器(qi)停(ting)振(zhen)(zhen)蕩時(shi)，“C”端無振(zhen)(zhen)蕩信號(hao)(hao)，又由(you)于二(er)極(ji)(ji)(ji)管VD2接在VT2發射(she)極(ji)(ji)(ji)與地之間，VT2基(ji)極(ji)(ji)(ji)被反向偏置，VT2處于可靠的(de)(de)截止狀態，VT2集(ji)電(dian)(dian)(dian)極(ji)(ji)(ji)為(wei)(wei)高(gao)電(dian)(dian)(dian)平(ping)，經(jing)過(guo)(guo)濾波器(qi)，在R4上(shang)得(de)到(dao)高(gao)電(dian)(dian)(dian)平(ping)信號(hao)(hao)。由(you)此可見，當(dang)高(gao)頻振(zhen)(zhen)蕩器(qi)正常工(gong)作時(shi)，在R4上(shang)得(de)到(dao)低電(dian)(dian)(dian)平(ping)信號(hao)(hao)，停(ting)振(zhen)(zhen)時(shi)，為(wei)(wei)高(gao)電(dian)(dian)(dian)平(ping)，由(you)此完成(cheng)了對振(zhen)(zhen)蕩器(qi)工(gong)作狀態的(de)(de)檢測(ce)。
3、音頻振蕩器
音頻振(zhen)(zhen)蕩(dang)(dang)器(qi)(qi)(qi)采用互補(bu)型(xing)(xing)多諧振(zhen)(zhen)蕩(dang)(dang)器(qi)(qi)(qi)，由(you)三極(ji)管(guan)VT3、VT4，電(dian)(dian)(dian)阻器(qi)(qi)(qi)R5、R7、 R8和(he)(he)(he)電(dian)(dian)(dian)容器(qi)(qi)(qi)C6組(zu)成。互補(bu)型(xing)(xing)多諧振(zhen)(zhen)蕩(dang)(dang)器(qi)(qi)(qi)采用兩只不同類型(xing)(xing)的(de)三極(ji)管(guan)，其(qi)中VT3為NPN型(xing)(xing)三極(ji)管(guan)，VT4為PNP型(xing)(xing)三極(ji)管(guan)，連(lian)接成互補(bu)的(de)、能(neng)(neng)夠強化正反饋的(de)電(dian)(dian)(dian)路。在電(dian)(dian)(dian)路工作時，它們(men)能(neng)(neng)夠交(jiao)替地(di)進(jin)入(ru)導通和(he)(he)(he)截止狀(zhuang)態，產生音頻振(zhen)(zhen)蕩(dang)(dang)。R7既(ji)是VT3負載電(dian)(dian)(dian)阻器(qi)(qi)(qi)，又是VT3導通時VT4基極(ji)限流(liu)電(dian)(dian)(dian)阻器(qi)(qi)(qi)。R8是 VT4集電(dian)(dian)(dian)極(ji)負載電(dian)(dian)(dian)阻器(qi)(qi)(qi)，振(zhen)(zhen)蕩(dang)(dang)脈沖信號(hao)由(you)VT4集電(dian)(dian)(dian)極(ji)輸出。R5和(he)(he)(he)C6等是反饋電(dian)(dian)(dian)阻器(qi)(qi)(qi)和(he)(he)(he)電(dian)(dian)(dian)容器(qi)(qi)(qi)，其(qi)數值大小影響(xiang)振(zhen)(zhen)蕩(dang)(dang)頻率(lv)的(de)高低(di)。
4、功率放大器
功率放(fang)大器(qi)(qi)(qi)由三極管VT5、揚聲器(qi)(qi)(qi)BL等組成(cheng)。從多諧振蕩器(qi)(qi)(qi)輸(shu)出的(de)正脈(mo)沖音頻信號經限流(liu)電阻(zu)器(qi)(qi)(qi)R9輸(shu)入到VT5的(de)基極，使其導(dao)通，在BL產生瞬時較強的(de)電流(liu)，驅動揚聲器(qi)(qi)(qi)發聲。由于(yu)VT5處于(yu)開關(guan)工作狀態，而導(dao)通時間又非(fei)常短，因此(ci)功率放(fang)大器(qi)(qi)(qi)非(fei)常省電，可以利(li)用9V積層(ceng)電池供電。
二、手持式金屬探測器原理是什么
了解了手持金屬探(tan)測(ce)器的(de)結(jie)構，接下來就可以介紹(shao)金屬探(tan)測(ce)器的(de)工(gong)作原理了：
手持金屬探測器利(li)用(yong)電磁(ci)感(gan)(gan)應的原理，利(li)用(yong)有(you)交流電通過(guo)的線圈(quan)，產生(sheng)迅速變化(hua)的磁(ci)場。這個磁(ci)場能在(zai)金屬物體(ti)內(nei)部能感(gan)(gan)生(sheng)渦電流。渦電流又(you)會產生(sheng)磁(ci)場，倒(dao)過(guo)來影(ying)響原來的磁(ci)場，引發(fa)探測(ce)器發(fa)出鳴聲(sheng)。
工作(zuo)時(shi)，其(qi)內部探測器(qi)會(hui)發(fa)出(chu)(chu)某一頻(pin)率的電(dian)磁(ci)波，由于(yu)金屬有(you)自感，會(hui)使(shi)這一頻(pin)率發(fa)生偏移，當(dang)它再接收到(dao)有(you)偏差的電(dian)磁(ci)波時(shi)，就把差頻(pin)放大，發(fa)出(chu)(chu)信(xin)號報警。
