手持金屬探測器原理

一、什么是手(shou)持金屬探(tan)測(ce)器(qi)

手持(chi)金(jin)屬(shu)探(tan)測器(qi)(qi)具有探(tan)測度(du)廣、定位準確、分辨力強、操(cao)作簡(jian)易等特點。手持(chi)金(jin)屬(shu)探(tan)測器(qi)(qi)主要是用探(tan)測和識別隱(yin)埋地下的金(jin)屬(shu)物。它除(chu)了在軍事上應用外，還廣泛用于:安全檢查(cha)、考(kao)古、探(tan)礦(kuang)，尋找廢舊金(jin)屬(shu);是廢舊金(jin)屬(shu)物回收(shou)的好幫(bang)手。

手持金屬探(tan)測器(qi)利用(yong)電磁(ci)(ci)感應的原理(li)，利用(yong)有交流電通過的線圈，產生迅速(su)變化的磁(ci)(ci)場(chang)。這個磁(ci)(ci)場(chang)能在金屬物(wu)體內部能感生渦(wo)電流。渦(wo)電流又(you)會(hui)產生磁(ci)(ci)場(chang)，倒過來(lai)影響原來(lai)的磁(ci)(ci)場(chang)，引(yin)發探(tan)測器(qi)發出鳴聲。

靈敏度控制可(ke)以(yi)幫助控制談(tan)扯呢器的(de)(de)磁(ci)(ci)場，減(jian)輕電(dian)磁(ci)(ci)干(gan)擾對(dui)其的(de)(de)影響(xiang)，在遇到干(gan)擾的(de)(de)時候，降低探測線圈所產生磁(ci)(ci)場的(de)(de)的(de)(de)靈敏度，可(ke)以(yi)減(jian)弱外部電(dian)磁(ci)(ci)干(gan)擾的(de)(de)影響(xiang)，從而使(shi)探測器工作正常進行。

金(jin)(jin)屬(shu)埋藏在地(di)下，透過厚(hou)厚(hou)的(de)(de)土(tu)(tu)層去探(tan)測，必然會(hui)受到地(di)質(zhi)(zhi)結構的(de)(de)影響(xiang)。土(tu)(tu)層中含有(you)各種各樣的(de)(de)礦物(wu)(wu)質(zhi)(zhi)，它們也會(hui)使探(tan)測器(qi)產(chan)生信(xin)號(hao)(hao)，這些礦物(wu)(wu)質(zhi)(zhi)的(de)(de)信(xin)號(hao)(hao)會(hui)掩蓋掉金(jin)(jin)屬(shu)的(de)(de)信(xin)號(hao)(hao)從而造(zao)成誤報(bao)警。用過國產(chan)手持金(jin)(jin)屬(shu)探(tan)測器(qi)的(de)(de)人都(dou)(dou)會(hui)有(you)這樣的(de)(de)體會(hui)，隨著(zhu)靠近(jin)土(tu)(tu)堆、石(shi)頭、磚(zhuan)頭都(dou)(dou)會(hui)發出報(bao)警音，這種現象成為“礦化反應(ying)”。由(you)于這個原因，國產(chan)手持金(jin)(jin)屬(shu)探(tan)測器(qi)只(zhi)能探(tan)測到淺層地(di)表的(de)(de)金(jin)(jin)屬(shu)物(wu)(wu)，賞金(jin)(jin)獵人金(jin)(jin)屬(shu)探(tan)測器(qi)裝有(you)先(xian)進的(de)(de)地(di)平衡系統(tong)，能排除一切礦化反應(ying)，大大提高了儀器(qi)的(de)(de)探(tan)測深(shen)度(du)跟效果。

所有手持探(tan)(tan)測(ce)儀器的(de)(de)探(tan)(tan)測(ce)深(shen)(shen)(shen)度(du)跟被探(tan)(tan)測(ce)金(jin)屬(shu)的(de)(de)面積、形狀、重量(liang)、埋(mai)藏(zang)時間、土(tu)質、土(tu)壤潮濕度(du)、使用者的(de)(de)熟練程度(du)，都有很大的(de)(de)關系，一般(ban)來(lai)說，面積越(yue)大，數量(liang)越(yue)多，土(tu)壤潮濕度(du)越(yue)小，密度(du)越(yue)低，埋(mai)藏(zang)時間越(yue)長，越(yue)有利(li)于增加探(tan)(tan)測(ce)器的(de)(de)探(tan)(tan)測(ce)深(shen)(shen)(shen)度(du)。儀器所標的(de)(de)深(shen)(shen)(shen)度(du)，是按照(zhao)產品(pin)的(de)(de)工業標準在最佳的(de)(de)情(qing)(qing)況(kuang)下所能(neng)達到的(de)(de)最大深(shen)(shen)(shen)度(du)。此外，在電(dian)量(liang)較低的(de)(de)情(qing)(qing)況(kuang)下，發射(she)功率不足的(de)(de)情(qing)(qing)況(kuang)下，也會衰減探(tan)(tan)測(ce)深(shen)(shen)(shen)度(du)，這(zhe)種情(qing)(qing)況(kuang)下，需要(yao)及時更換電(dian)池。

二、手持金屬探(tan)測器的原理

框圖

由(you)手(shou)持(chi)金屬探測(ce)器(qi)的電路框圖可以看(kan)出，本手(shou)持(chi)金屬探測(ce)器(qi)由(you)高頻振蕩器(qi)、振蕩檢測(ce)器(qi)、音頻振蕩器(qi)和(he)功率放大器(qi)等(deng)組(zu)成。

高頻振蕩器

由(you)三極(ji)(ji)管(guan)VT1和(he)(he)(he)高頻(pin)(pin)變壓(ya)(ya)(ya)(ya)(ya)器(qi)(qi)(qi)T1等組成(cheng)(cheng)(cheng)，是(shi)一種變壓(ya)(ya)(ya)(ya)(ya)器(qi)(qi)(qi)反(fan)(fan)饋(kui)(kui)型LC振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)器(qi)(qi)(qi)。T1的(de)(de)(de)(de)(de)初級(ji)(ji)線(xian)圈L1和(he)(he)(he)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)器(qi)(qi)(qi)C1組成(cheng)(cheng)(cheng)LC并聯振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)回路，其(qi)振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)頻(pin)(pin)率約200kHz，由(you)L1的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)感量和(he)(he)(he)C1的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)量決定。T1的(de)(de)(de)(de)(de)次級(ji)(ji)線(xian)圈L2作(zuo)為(wei)(wei)(wei)振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)器(qi)(qi)(qi)的(de)(de)(de)(de)(de)反(fan)(fan)饋(kui)(kui)線(xian)圈，其(qi)“C”端(duan)(duan)接振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)管(guan)VT1的(de)(de)(de)(de)(de)基極(ji)(ji)，“D”端(duan)(duan)接VD2。由(you)于VD2處(chu)于正(zheng)向(xiang)導(dao)通(tong)狀態，對高頻(pin)(pin)信(xin)號(hao)來(lai)說(shuo)，“D”端(duan)(duan)可視為(wei)(wei)(wei)接地。在高頻(pin)(pin)變壓(ya)(ya)(ya)(ya)(ya)器(qi)(qi)(qi)T1中(zhong)，如果“A” 和(he)(he)(he)“D”端(duan)(duan)分別為(wei)(wei)(wei)初、次級(ji)(ji)線(xian)圈繞線(xian)方向(xiang)的(de)(de)(de)(de)(de)首(shou)端(duan)(duan)，則從(cong)“C”端(duan)(duan)輸入(ru)到振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)管(guan)VT1基極(ji)(ji)的(de)(de)(de)(de)(de)反(fan)(fan)饋(kui)(kui)信(xin)號(hao)，能(neng)夠使電(dian)(dian)(dian)(dian)(dian)(dian)路形成(cheng)(cheng)(cheng)正(zheng)反(fan)(fan)饋(kui)(kui)而產生自激(ji)高頻(pin)(pin)振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)。振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)器(qi)(qi)(qi)反(fan)(fan)饋(kui)(kui)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)的(de)(de)(de)(de)(de)大(da)(da)小與線(xian)圈L1、L2的(de)(de)(de)(de)(de)匝數(shu)比有(you)關，匝數(shu)比過小，由(you)于反(fan)(fan)饋(kui)(kui)太弱，不容(rong)易起振(zhen)(zhen)(zhen)，過大(da)(da)引起振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)波形失(shi)真，還會使手持金(jin)(jin)屬探測(ce)器(qi)(qi)(qi)靈(ling)敏度大(da)(da)為(wei)(wei)(wei)降低(di)。振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)管(guan)VT1的(de)(de)(de)(de)(de)偏(pian)置電(dian)(dian)(dian)(dian)(dian)(dian)路由(you)R2和(he)(he)(he)二(er)極(ji)(ji)管(guan)VD2組成(cheng)(cheng)(cheng)，R2為(wei)(wei)(wei)VD2的(de)(de)(de)(de)(de)限(xian)流電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)。由(you)于二(er)極(ji)(ji)管(guan)正(zheng)向(xiang)閾值電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)恒定(約0.7V)，通(tong)過次級(ji)(ji)線(xian)圈L2加到VT1的(de)(de)(de)(de)(de)基極(ji)(ji)，以得(de)到穩(wen)(wen)定的(de)(de)(de)(de)(de)偏(pian)置電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)。顯然，這種穩(wen)(wen)壓(ya)(ya)(ya)(ya)(ya)式的(de)(de)(de)(de)(de)偏(pian)置電(dian)(dian)(dian)(dian)(dian)(dian)路能(neng)夠大(da)(da)大(da)(da)增強(qiang)VT1高頻(pin)(pin)振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)器(qi)(qi)(qi)的(de)(de)(de)(de)(de)穩(wen)(wen)定性。為(wei)(wei)(wei)了進一步提高手持金(jin)(jin)屬探測(ce)器(qi)(qi)(qi)的(de)(de)(de)(de)(de)可靠性和(he)(he)(he)靈(ling)敏度，高頻(pin)(pin)振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)器(qi)(qi)(qi)通(tong)過穩(wen)(wen)壓(ya)(ya)(ya)(ya)(ya)電(dian)(dian)(dian)(dian)(dian)(dian)路供電(dian)(dian)(dian)(dian)(dian)(dian)，其(qi)電(dian)(dian)(dian)(dian)(dian)(dian)路由(you)穩(wen)(wen)壓(ya)(ya)(ya)(ya)(ya)二(er)極(ji)(ji)管(guan)VD1、限(xian)流電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)器(qi)(qi)(qi)R6和(he)(he)(he)去耦(ou)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)器(qi)(qi)(qi)C5組成(cheng)(cheng)(cheng)。振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)管(guan)VT1發射極(ji)(ji)與地之間(jian)接有(you)兩個(ge)串(chuan)聯的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)位器(qi)(qi)(qi)，具有(you)發射極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)(dian)流負(fu)反(fan)(fan)饋(kui)(kui)作(zuo)用，其(qi)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)值越大(da)(da)，負(fu)反(fan)(fan)饋(kui)(kui)作(zuo)用越強(qiang)，VT1的(de)(de)(de)(de)(de)放(fang)大(da)(da)能(neng)力也就越低(di)，甚至于使電(dian)(dian)(dian)(dian)(dian)(dian)路停振(zhen)(zhen)(zhen)。RP1為(wei)(wei)(wei)振(zhen)(zhen)(zhen)蕩(dang)(dang)(dang)器(qi)(qi)(qi)增益的(de)(de)(de)(de)(de)粗調電(dian)(dian)(dian)(dian)(dian)(dian)位器(qi)(qi)(qi)，RP2為(wei)(wei)(wei)細調電(dian)(dian)(dian)(dian)(dian)(dian)位器(qi)(qi)(qi)。

振蕩檢測器

振(zhen)蕩檢(jian)測(ce)器(qi)(qi)由三極(ji)管(guan)(guan)(guan)開(kai)(kai)關電(dian)(dian)(dian)路和濾波(bo)(bo)(bo)電(dian)(dian)(dian)路組成。開(kai)(kai)關電(dian)(dian)(dian)路由三極(ji)管(guan)(guan)(guan)VT2、二極(ji)管(guan)(guan)(guan) VD2等組成，濾波(bo)(bo)(bo)電(dian)(dian)(dian)路由濾波(bo)(bo)(bo)電(dian)(dian)(dian)阻(zu)(zu)器(qi)(qi)R3，濾波(bo)(bo)(bo)電(dian)(dian)(dian)容器(qi)(qi)C2、C3和C4組成。在(zai)開(kai)(kai)關電(dian)(dian)(dian)路中，VT2的(de)基極(ji)與次級線圈(quan)L2的(de)“C”端相連，當(dang)高(gao)頻振(zhen)蕩器(qi)(qi)工作(zuo)(zuo)時，經(jing)(jing)高(gao)頻變(bian)壓器(qi)(qi)T1耦合過來的(de)振(zhen)蕩信(xin)(xin)號(hao)(hao)，正(zheng)半周(zhou)使VT2導通，VT2集電(dian)(dian)(dian)極(ji)輸出(chu)負脈沖信(xin)(xin)號(hao)(hao)，經(jing)(jing)過π型RC濾波(bo)(bo)(bo)器(qi)(qi)，在(zai)負載電(dian)(dian)(dian)阻(zu)(zu)器(qi)(qi)R4上(shang)輸出(chu)低電(dian)(dian)(dian)平信(xin)(xin)號(hao)(hao)。當(dang)高(gao)頻振(zhen)蕩器(qi)(qi)停振(zhen)蕩時，“C”端無振(zhen)蕩信(xin)(xin)號(hao)(hao)，又(you)由于(yu)二極(ji)管(guan)(guan)(guan)VD2接在(zai)VT2發射極(ji)與地之(zhi)間，VT2基極(ji)被(bei)反向偏(pian)置，VT2處于(yu)可(ke)靠的(de)截止(zhi)狀態，VT2集電(dian)(dian)(dian)極(ji)為高(gao)電(dian)(dian)(dian)平，經(jing)(jing)過濾波(bo)(bo)(bo)器(qi)(qi)，在(zai)R4上(shang)得(de)到高(gao)電(dian)(dian)(dian)平信(xin)(xin)號(hao)(hao)。由此(ci)可(ke)見，當(dang)高(gao)頻振(zhen)蕩器(qi)(qi)正(zheng)常工作(zuo)(zuo)時，在(zai)R4上(shang)得(de)到低電(dian)(dian)(dian)平信(xin)(xin)號(hao)(hao)，停振(zhen)時，為高(gao)電(dian)(dian)(dian)平，由此(ci)完成了對振(zhen)蕩器(qi)(qi)工作(zuo)(zuo)狀態的(de)檢(jian)測(ce)。

音頻振蕩器

音(yin)頻振蕩(dang)(dang)器采用(yong)互(hu)補型多(duo)(duo)諧(xie)振蕩(dang)(dang)器，由(you)三(san)極(ji)管(guan)VT3、VT4，電(dian)阻(zu)(zu)器R5、R7、 R8和(he)電(dian)容器C6組成。互(hu)補型多(duo)(duo)諧(xie)振蕩(dang)(dang)器采用(yong)兩只不同類型的三(san)極(ji)管(guan)，其中VT3為(wei)NPN型三(san)極(ji)管(guan)，VT4為(wei)PNP型三(san)極(ji)管(guan)，連接(jie)成互(hu)補的、能(neng)夠(gou)強化(hua)正(zheng)反饋的電(dian)路。在電(dian)路工(gong)作時，它們能(neng)夠(gou)交替地(di)進入(ru)導(dao)通和(he)截止狀態，產生音(yin)頻振蕩(dang)(dang)。R7既是(shi)VT3負載電(dian)阻(zu)(zu)器，又是(shi)VT3導(dao)通時VT4基極(ji)限(xian)流電(dian)阻(zu)(zu)器。R8是(shi) VT4集(ji)電(dian)極(ji)負載電(dian)阻(zu)(zu)器，振蕩(dang)(dang)脈(mo)沖信號由(you)VT4集(ji)電(dian)極(ji)輸出。R5和(he)C6等是(shi)反饋電(dian)阻(zu)(zu)器和(he)電(dian)容器，其數(shu)值大小影響振蕩(dang)(dang)頻率(lv)的高(gao)低。

功率放大器

功率放大器(qi)(qi)由(you)三極(ji)管(guan)VT5、揚聲器(qi)(qi)BL等組成。從多諧振蕩器(qi)(qi)輸(shu)出的(de)(de)(de)正(zheng)脈(mo)沖音頻信(xin)號經限流電阻器(qi)(qi)R9輸(shu)入到VT5的(de)(de)(de)基極(ji)，使其導(dao)通(tong)，在BL產(chan)生瞬時較強的(de)(de)(de)電流，驅動揚聲器(qi)(qi)發聲。由(you)于VT5處于開關工作狀(zhuang)態，而導(dao)通(tong)時間又非常(chang)(chang)短，因(yin)此功率放大器(qi)(qi)非常(chang)(chang)省電，可以利(li)用(yong)9V積層電池供電。

調節(jie)高(gao)頻振(zhen)(zhen)蕩(dang)(dang)器(qi)(qi)的(de)(de)增(zeng)益電(dian)(dian)位(wei)器(qi)(qi)，恰好使振(zhen)(zhen)蕩(dang)(dang)器(qi)(qi)處于(yu)臨界振(zhen)(zhen)蕩(dang)(dang)狀態(tai)(tai)，也就(jiu)是說剛好使振(zhen)(zhen)蕩(dang)(dang)器(qi)(qi)起振(zhen)(zhen)。當探測線圈L1靠近金(jin)屬物(wu)體時，由于(yu)電(dian)(dian)磁感應現象，會在金(jin)屬導體中產生渦電(dian)(dian)流，使振(zhen)(zhen)蕩(dang)(dang)回(hui)路中的(de)(de)能(neng)量損耗增(zeng)大，正(zheng)反饋減(jian)弱，處于(yu)臨界態(tai)(tai)的(de)(de)振(zhen)(zhen)蕩(dang)(dang)器(qi)(qi)振(zhen)(zhen)蕩(dang)(dang)減(jian)弱，甚至無(wu)法維(wei)持振(zhen)(zhen)蕩(dang)(dang)所需的(de)(de)最低(di)能(neng)量而停振(zhen)(zhen)。如果能(neng)檢(jian)測出這種變化，并轉換成聲音(yin)信號，根據聲音(yin)有無(wu)，就(jiu)可以判定探測線圈下面是否有金(jin)屬物(wu)體了。

互補(bu)型(xing)多諧振蕩器的工作原理

接通電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)時(shi)，由(you)(you)于VT3基(ji)(ji)極(ji)(ji)接有(you)偏置(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)器(qi)(qi)R1、R3而被正(zheng)向(xiang)(xiang)(xiang)偏置(zhi)，假設(she)VT3集電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)處于上(shang)升(sheng)階(jie)段，VT4基(ji)(ji)極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)隨之(zhi)上(shang)升(sheng)，導(dao)(dao)致(zhi)VT4集電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)劇增(zeng)，VT4集電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)隨之(zhi)迅速升(sheng)高(gao)，由(you)(you)VT4輸(shu)出(chu)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)通過(guo)與之(zhi)相連的(de)(de)R5向(xiang)(xiang)(xiang)C6 充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，流(liu)(liu)經(jing)(jing)VT3的(de)(de)基(ji)(ji)極(ji)(ji)入(ru)(ru)(ru)地，又(you)(you)導(dao)(dao)致(zhi)VT3基(ji)(ji)極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)進(jin)一(yi)步(bu)升(sheng)高(gao)。如此反(fan)復(fu)循(xun)環，強(qiang)烈(lie)的(de)(de)正(zheng)反(fan)饋(kui)使(shi)得(de)VT3、VT4迅速進(jin)入(ru)(ru)(ru)飽和(he)(he)(he)導(dao)(dao)通狀態(tai)(tai)(tai)，VT4集電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)處于高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)，使(shi)多(duo)諧(xie)振(zhen)(zhen)(zhen)蕩(dang)器(qi)(qi)進(jin)入(ru)(ru)(ru)第(di)一(yi)個暫(zan)穩(wen)態(tai)(tai)(tai)過(guo)程(cheng)。隨著電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)通過(guo)飽和(he)(he)(he)導(dao)(dao)通的(de)(de)VT4經(jing)(jing)R5向(xiang)(xiang)(xiang)C6充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，當(dang)VT3基(ji)(ji)極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)下降到(dao)一(yi)定程(cheng)度時(shi)，VT3退(tui)出(chu)飽和(he)(he)(he)導(dao)(dao)通狀態(tai)(tai)(tai)，集電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)開始(shi)減(jian)小(xiao)，導(dao)(dao)致(zhi)VT4集電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)減(jian)小(xiao)，VT4集電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)下降，這一(yi)過(guo)程(cheng)又(you)(you)進(jin)一(yi)步(bu)加劇了(le)向(xiang)(xiang)(xiang)C6充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)迅速減(jian)小(xiao)，VT3基(ji)(ji)極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)急劇降低而使(shi) VT3截(jie)止，VT4集電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)迅速跌至(zhi)(zhi)低電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)，多(duo)諧(xie)振(zhen)(zhen)(zhen)蕩(dang)器(qi)(qi)翻轉(zhuan)到(dao)第(di)二個暫(zan)穩(wen)態(tai)(tai)(tai)。多(duo)諧(xie)振(zhen)(zhen)(zhen)蕩(dang)器(qi)(qi)剛(gang)進(jin)入(ru)(ru)(ru)第(di)二暫(zan)穩(wen)態(tai)(tai)(tai)時(shi)，先前(qian)向(xiang)(xiang)(xiang)C6充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)結(jie)(jie)果，其(qi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容器(qi)(qi)右端(duan)(duan)(duan)為(wei)正(zheng)，左端(duan)(duan)(duan)為(wei)負(fu)，現在(zai)C6右端(duan)(duan)(duan)對(dui)地為(wei)低電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)，由(you)(you)于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容器(qi)(qi)C6兩(liang)端(duan)(duan)(duan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓不能躍變，故VT3基(ji)(ji)極(ji)(ji)被C6左端(duan)(duan)(duan)負(fu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)強(qiang)烈(lie)反(fan)向(xiang)(xiang)(xiang)偏置(zhi)，使(shi)兩(liang)只三極(ji)(ji)管(guan)在(zai)較長(chang)時(shi)間繼續保持截(jie)止狀態(tai)(tai)(tai)。在(zai)C6放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)時(shi)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)從(cong)(cong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容器(qi)(qi)右端(duan)(duan)(duan)流(liu)(liu)出(chu)，主要流(liu)(liu)經(jing)(jing)R5、(R8)、R9、VT5發射結(jie)(jie)入(ru)(ru)(ru)地，又(you)(you)經(jing)(jing)過(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)、R6、R1、R3流(liu)(liu)回電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容器(qi)(qi)C6左端(duan)(duan)(duan)。直到(dao)C6 放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)結(jie)(jie)束，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)繼續通過(guo)上(shang)述回路開始(shi)對(dui)C6反(fan)向(xiang)(xiang)(xiang)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，C6左端(duan)(duan)(duan)為(wei)正(zheng)。當(dang)C6兩(liang)端(duan)(duan)(duan)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)上(shang)升(sheng)至(zhi)(zhi)0.7V，VT3開始(shi)進(jin)入(ru)(ru)(ru)導(dao)(dao)通狀態(tai)(tai)(tai)，經(jing)(jing)過(guo)強(qiang)烈(lie)正(zheng)反(fan)饋(kui)，迅速進(jin)入(ru)(ru)(ru)飽和(he)(he)(he)導(dao)(dao)通狀態(tai)(tai)(tai)，使(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路再次發生翻轉(zhuan)，重復(fu)先前(qian)的(de)(de)暫(zan)穩(wen)態(tai)(tai)(tai)過(guo)程(cheng)，如此周而復(fu)始(shi)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路產(chan)生自激多(duo)諧(xie)振(zhen)(zhen)(zhen)蕩(dang)。從(cong)(cong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路工(gong)作過(guo)程(cheng)可以看出(chu)，向(xiang)(xiang)(xiang)C6充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)時(shi)，充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)器(qi)(qi)R5 電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)值較小(xiao)，因(yin)(yin)此充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)過(guo)程(cheng)較快，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路處在(zai)飽和(he)(he)(he)導(dao)(dao)通狀態(tai)(tai)(tai)時(shi)間很短;而在(zai)C6放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)時(shi)，需要流(liu)(liu)經(jing)(jing)許多(duo)有(you)關(guan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)器(qi)(qi)，放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)器(qi)(qi)總的(de)(de)數值較大，因(yin)(yin)而放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)過(guo)程(cheng)較慢，也就是說電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路處于截(jie)止時(shi)間較長(chang)。因(yin)(yin)此，從(cong)(cong)VT4集電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)輸(shu)出(chu)波形占空比很大，正(zheng)脈(mo)沖信號(hao)的(de)(de)脈(mo)寬(kuan)很窄，其(qi)振(zhen)(zhen)(zhen)蕩(dang)頻率約330Hz 。

調試與使用方法

手持金(jin)屬探測(ce)器(qi)電(dian)(dian)路除了靈敏度調節電(dian)(dian)位器(qi)外，沒有調整(zheng)部分，只要焊接無誤，電(dian)(dian)路就能正常工(gong)作。整(zheng)機(ji)在(zai)靜態，也(ye)就是揚聲器(qi)不發(fa)聲時，總(zong)電(dian)(dian)流(liu)約(yue)為10mA，探測(ce)到(dao)金(jin)屬揚聲器(qi)發(fa)出聲音時，整(zheng)機(ji)電(dian)(dian)流(liu)上(shang)升到(dao)20mA。一個新的積層(ceng)電(dian)(dian)池可(ke)以工(gong)作20~30小時。

新焊(han)接的手持金屬探測器(qi)如果不(bu)能正常工作，首先要檢查(cha)電(dian)(dian)路板上(shang)各元器(qi)件(jian)、接線(xian)(xian)焊(han)接是(shi)否有(you)誤，再測量(liang)電(dian)(dian)池電(dian)(dian)壓(ya)及(ji)供電(dian)(dian)回路是(shi)否正常，穩(wen)(wen)壓(ya)二極管VD1穩(wen)(wen)定電(dian)(dian)壓(ya)5.5~6.5V之間，VD2極性不(bu)要焊(han)反。探測碟內振蕩線(xian)(xian)圈(quan)初次級及(ji)首尾端(duan)不(bu)要焊(han)錯(cuo)。

手(shou)(shou)持金屬(shu)探測(ce)器(qi)(qi)使(shi)用(yong)前，需要(yao)調整探測(ce)桿的長度(du)，只要(yao)將黑(hei)膠(jiao)(jiao)通(tong)(tong)(tong)旋(xuan)(xuan)松，推拉(la)膠(jiao)(jiao)通(tong)(tong)(tong)套管至適宜的長度(du)，再旋(xuan)(xuan)轉膠(jiao)(jiao)內通(tong)(tong)(tong)管，使(shi)電(dian)纜(lan)線繞緊(jin)，并(bing)使(shi)手(shou)(shou)柄(bing)尖端朝上，最后將黑(hei)膠(jiao)(jiao)通(tong)(tong)(tong)旋(xuan)(xuan)緊(jin)，鎖住(zhu)膠(jiao)(jiao)通(tong)(tong)(tong)套管。這樣，手(shou)(shou)握探測(ce)器(qi)(qi)手(shou)(shou)柄(bing)時，大拇指正好緊(jin)挨靈敏(min)度(du)調節電(dian)位器(qi)(qi)。

調(diao)整手(shou)持金(jin)(jin)(jin)屬(shu)探測(ce)器(qi)(qi)(qi)靈敏(min)度時(shi)，探測(ce)碟(die)(振蕩線圈)要遠離金(jin)(jin)(jin)屬(shu)，包括帶(dai)鋁(lv)箔的(de)紙張，然后旋轉(zhuan)靈敏(min)度細調(diao)電(dian)(dian)位器(qi)(qi)(qi)旋鈕(niu)(FINE TUNING)打開電(dian)(dian)源(yuan)開關，并旋轉(zhuan)到一半(ban)的(de)位置，再(zai)調(diao)節粗調(diao)電(dian)(dian)位器(qi)(qi)(qi)旋鈕(niu)(TUNING)，使揚(yang)聲(sheng)(sheng)器(qi)(qi)(qi)音(yin)頻叫(jiao)聲(sheng)(sheng)停止，最后再(zai)微調(diao)細調(diao)電(dian)(dian)位器(qi)(qi)(qi)，使揚(yang)聲(sheng)(sheng)器(qi)(qi)(qi)叫(jiao)聲(sheng)(sheng)剛好停止，這(zhe)時(shi)手(shou)持金(jin)(jin)(jin)屬(shu)探測(ce)器(qi)(qi)(qi)的(de)靈敏(min)度最高。用手(shou)持金(jin)(jin)(jin)屬(shu)探測(ce)器(qi)(qi)(qi)探測(ce)金(jin)(jin)(jin)屬(shu)時(shi)，只要探測(ce)碟(die)靠(kao)近任何金(jin)(jin)(jin)屬(shu)，揚(yang)聲(sheng)(sheng)器(qi)(qi)(qi)便(bian)會發(fa)出聲(sheng)(sheng)音(yin)，遠離到一定位置叫(jiao)聲(sheng)(sheng)自動停止。

本手(shou)持(chi)金(jin)屬(shu)(shu)探(tan)測(ce)(ce)(ce)(ce)器(qi)(qi)有較高的(de)(de)靈敏度，用它探(tan)測(ce)(ce)(ce)(ce)大塊(kuai)金(jin)屬(shu)(shu)時，探(tan)測(ce)(ce)(ce)(ce)碟(die)距金(jin)屬(shu)(shu)物(wu)體 500px揚(yang)聲器(qi)(qi)就會發出聲音(yin)，小(xiao)到曲別針(zhen)，甚(shen)至(zhi)一枚大頭針(zhen)都能檢(jian)測(ce)(ce)(ce)(ce)到，只是探(tan)測(ce)(ce)(ce)(ce)碟(die)線圈必須緊靠細小(xiao)金(jin)屬(shu)(shu)物(wu)體。由于手(shou)持(chi)金(jin)屬(shu)(shu)探(tan)測(ce)(ce)(ce)(ce)器(qi)(qi)利用振蕩線圈的(de)(de)電磁感(gan)應來(lai)探(tan)測(ce)(ce)(ce)(ce)金(jin)屬(shu)(shu)物(wu)體，可以(yi)透過非金(jin)屬(shu)(shu)物(wu)體，比如紙(zhi)張、木材(cai)、塑料、磚石、土(tu)壤(rang)、甚(shen)至(zhi)水層，探(tan)測(ce)(ce)(ce)(ce)到被遮蓋的(de)(de)的(de)(de)金(jin)屬(shu)(shu)物(wu)體，因(yin)此(ci)具(ju)有實用性，比如在裝修房(fang)屋時，用它探(tan)測(ce)(ce)(ce)(ce)到墻內的(de)(de)電線或鋼筋，以(yi)免(mian)造(zao)成(cheng)施工(gong)危險和安全隱患;又如安檢(jian)用的(de)(de)手(shou)持(chi)金(jin)屬(shu)(shu)探(tan)測(ce)(ce)(ce)(ce)器(qi)(qi)就是根據這個原理制成(cheng)的(de)(de)