監(jian)視(shi)器作為(wei)矩(ju)陣控制系統(tong)的(de)監(jian)視(shi)器終端時(shi)，為(wei)什(shen)么在矩(ju)陣控制器切換圖像是會出現一段時(shi)間(jian)的(de)不(bu)同步現象?

在(zai)監(jian)控(kong)(kong)系(xi)統(tong)(tong)中，每路前端設備(bei)(如攝像機)等輸出(chu)的圖(tu)像信(xin)號(hao)(hao)中的場同(tong)(tong)步信(xin)號(hao)(hao)如果存(cun)在(zai)相(xiang)位差(cha)，則矩(ju)陣控(kong)(kong)制器(qi)(qi)切換各路圖(tu)像信(xin)號(hao)(hao)時(shi)(shi)，監(jian)視器(qi)(qi)便會(hui)出(chu)現一段時(shi)(shi)間的不同(tong)(tong)步現象(xiang)，相(xiang)位差(cha)越大，不同(tong)(tong)步的時(shi)(shi)間就越長。因(yin)此建議在(zai)構建監(jian)控(kong)(kong)系(xi)統(tong)(tong)時(shi)(shi)，應盡量選用帶有外同(tong)(tong)步輸入的前端設備(bei)，并且所(suo)有的前端設備(bei)均(jun)使(shi)(shi)用外同(tong)(tong)步方(fang)式，即各路圖(tu)像信(xin)號(hao)(hao)的同(tong)(tong)步都受同(tong)(tong)一同(tong)(tong)步信(xin)號(hao)(hao)控(kong)(kong)制，促使(shi)(shi)監(jian)視器(qi)(qi)屏幕顯示同(tong)(tong)步。
在使用(yong)監視(shi)器觀(guan)察圖像(xiang)時，為什么有時會出現(xian)圖像(xiang)扭(niu)曲、變形(xing)失(shi)真(zhen)、行(xing)場不(bu)同步甚至無輸入信號的(de)故障、現(xian)象?

1、監(jian)(jian)視(shi)器(qi)的行(xing)(xing)業標準規定(ding)，專(zhuan)業監(jian)(jian)視(shi)器(qi)的輸(shu)入(ru)(ru)信號(hao)幅度(du)為1Vp-P±3dB(約(yue)0.7Vp-P—1.4Vp-p)，輸(shu)入(ru)(ru)阻抗為75歐(ou)姆。因此(ci)，如(ru)果(guo)輸(shu)入(ru)(ru)信號(hao)由(you)于(yu)(yu)線纜衰減(jian)、阻抗不匹配(pei)或傳(chuan)輸(shu)電纜的BNC頭制作(zuo)不規范等(deng)原因，造成輸(shu)入(ru)(ru)信號(hao)幅度(du)遠低于(yu)(yu)0.7p-p;或者(zhe)由(you)于(yu)(yu)攝像機的輸(shu)出不規范或接入(ru)(ru)了某些(xie)不規范的接入(ru)(ru)設備(如(ru)分(fen)配(pei)器(qi)、放大器(qi)等(deng))導致輸(shu)入(ru)(ru)信號(hao)幅度(du)遠大于(yu)(yu)1.4Vp-p時，均有可(ke)能造成圖像失(shi)真、行(xing)(xing)場不同(tong)步等(deng)現象。

2、由于視(shi)頻(pin)頻(pin)率范(fan)圍較寬，視(shi)頻(pin)信號在(zai)傳(chuan)輸(shu)過程(cheng)中較易受到干擾(包括50Hz電(dian)源干擾，電(dian)磁波干擾等)，從而影響(xiang)圖像質量。干擾嚴重的可(ke)能造成圖像扭(niu)曲、變形、滾道、行場(chang)不(bu)同步。因此(ci)監控系(xi)統安裝(zhuang)過程(cheng)中，視(shi)頻(pin)線(xian)必須遠離電(dian)磁波干擾源。

3、前端設(she)(she)(she)備、控制主(zhu)機設(she)(she)(she)備及終(zhong)端設(she)(she)(she)備之間(jian)的(de)(de)電(dian)(dian)位有電(dian)(dian)位差也會干擾視頻(pin)信(xin)號，造(zao)成(cheng)圖像(xiang)(xiang)信(xin)號的(de)(de)畸變(bian)或(huo)圖像(xiang)(xiang)出現滾道，如(ru)果在整(zheng)個系(xi)統(tong)帶電(dian)(dian)接(jie)(jie)(jie)入(ru)時(即前端設(she)(she)(she)備、主(zhu)控設(she)(she)(she)備及終(zhong)端設(she)(she)(she)備均處(chu)于通電(dian)(dian)狀態(tai)下接(jie)(jie)(jie)入(ru)BNC頭連接(jie)(jie)(jie)前后端設(she)(she)(she)備時)，可能由于前后端設(she)(she)(she)備的(de)(de)地(di)線(xian)(實際上是(shi)便是(shi)傳輸(shu)(shu)電(dian)(dian)纜的(de)(de)屏蔽層)之間(jian)的(de)(de)電(dian)(dian)位差造(zao)成(cheng)地(di)對(dui)地(di)跳火，這一跳火嚴(yan)重時會擊毀(hui)輸(shu)(shu)入(ru)端的(de)(de)元(yuan)件或(huo)PCB板砂鍋內的(de)(de)地(di)級敷(fu)線(xian)。造(zao)成(cheng)輸(shu)(shu)入(ru)端開路，輸(shu)(shu)入(ru)無圖像(xiang)(xiang)故障。因(yin)此(ci)監控系(xi)統(tong)工(gong)(gong)程的(de)(de)建設(she)(she)(she)應(ying)(ying)嚴(yan)格按規范設(she)(she)(she)計、施工(gong)(gong)。接(jie)(jie)(jie)地(di)母線(xian)應(ying)(ying)采用足(zu)夠截面積的(de)(de)銅制導線(xian)，確保前后端的(de)(de)地(di)對(dui)地(di)電(dian)(dian)阻<1Ω，接(jie)(jie)(jie)地(di)線(xian)不得形(xing)成(cheng)封閉回路，不得與強電(dian)(dian)網零線(xian)短(duan)接(jie)(jie)(jie)或(huo)混接(jie)(jie)(jie)。