要了解如何分辨出一臺PoE交換機是否標準PoE供電，先要弄清楚什么是POE交換機。
PoE供(gong)(gong)電(dian)(dian)交(jiao)(jiao)換機是指能(neng)夠通過網(wang)線(xian)為遠(yuan)端受電(dian)(dian)終端提供(gong)(gong)網(wang)絡供(gong)(gong)電(dian)(dian)的(de)交(jiao)(jiao)換機，包含網(wang)絡交(jiao)(jiao)換機和PoE供(gong)(gong)電(dian)(dian)兩(liang)個(ge)功(gong)能(neng)，是PoE供(gong)(gong)電(dian)(dian)系統中比較常見的(de)供(gong)(gong)電(dian)(dian)設備(bei)。 POE交換機的分類 1、標準POE交換機 符合IEEE802.3af、802.3at標準，就是(shi)標準POE交(jiao)換(huan)機(俗稱48V)，完整(zheng)的POE包括供(gong)電(dian)(dian)端(duan)(duan)設(she)備(PSE,
Power Sourcing Equipment)和受(shou)電(dian)(dian)端(duan)(duan)設(she)備(PD, Power
Device)兩部分，poe交(jiao)換(huan)機為PSE設(she)備的一種。PSE是(shi)為終端(duan)(duan)供(gong)電(dian)(dian)的設(she)備,也是(shi)POE以太網(wang)供(gong)電(dian)(dian)過程的管理者。PD是(shi)接受(shou)供(gong)電(dian)(dian)的終端(duan)(duan)設(she)備(48V國(guo)標設(she)備含有PD芯(xin)片)。 2、非標準POE交(jiao)換機兩類。 相反為非標(biao)(biao)準POE交換機(“非標(biao)(biao)準”簡(jian)稱”非標(biao)(biao)”俗稱24V,但是非標(biao)(biao)有48V、24V、12V、5V等)。 POE交換機主流應用領域 POE交換機(ji)主(zhu)要給(gei)監(jian)控(kong)(給(gei)攝像(xiang)機(ji)供(gong)(gong)電(dian))、無(wu)線覆(fu)蓋(gai)(給(gei)AP供(gong)(gong)電(dian))、無(wu)線傳輸(給(gei)網橋供(gong)(gong)電(dian))等(deng)設(she)備提供(gong)(gong)網絡及電(dian)源。
標準POE供電交換機工作過程 1、檢測： poe交(jiao)換機先輸(shu)出很小的電(dian)壓,檢測到含(han)有支持IEEE802.3at/af標準芯片的受電(dian)端設備(支持IEEE802.3at/af標準芯片簡稱”PD”)。 2、PD分(fen)類：檢(jian)測到(dao)PD后(hou), poe交換機對PD設備(bei)進行(xing)分(fen)類,并(bing)評估PD設備(bei)的功率(lv)。 3、供電(dian)(dian)：在啟動期內(nei)(一般小于(yu)15μs), poe交換機(ji)從低電(dian)(dian)壓向PD供電(dian)(dian)，直到供夠PD所需的電(dian)(dian)壓，為PD設備供穩(wen)定(ding)可靠的直流(liu)電(dian)(dian)。 4、斷電(dian)：若PD設備斷開, poe交(jiao)換機會快速(su)(一般(ban)在300～400ms之內)停止對(dui)PD供(gong)電(dian),并重復檢測(ce)過程(cheng)以檢測(ce)線(xian)纜(lan)的終端是(shi)否(fou)連接PD設備。
真假POE用萬能表測試方法 啟動設備(bei)，將萬用(yong)(yong)(yong)電(dian)(dian)(dian)表(biao)調至(zhi)電(dian)(dian)(dian)壓(ya)測(ce)量檔位(wei)，用(yong)(yong)(yong)萬用(yong)(yong)(yong)電(dian)(dian)(dian)表(biao)兩表(biao)筆分別(bie)點觸PSE設備(bei)供(gong)電(dian)(dian)(dian)腳（通常是RJ45端口的1/2,3/6或者4/5,7/8），如果測(ce)出(chu)有48V或其(qi)它電(dian)(dian)(dian)壓(ya)值（12V、24V等）穩定(ding)輸出(chu)的設備(bei)即是非標產品。因(yin)為在這個過程中(zhong)，PSE不對受電(dian)(dian)(dian)設備(bei)（這里為萬用(yong)(yong)(yong)表(biao)）做(zuo)檢測(ce)，直(zhi)接采用(yong)(yong)(yong)48V或其(qi)它電(dian)(dian)(dian)壓(ya)值供(gong)電(dian)(dian)(dian)。 反(fan)之(zhi)，如果測(ce)量不(bu)出電壓(ya)，萬用表表針在(zai)2~10V之(zhi)間跳動，則為(wei)標準(zhun)PoE。因為(wei)在(zai)這個(ge)階段，PSE在(zai)對PD端（這里為(wei)萬用表）進行檢測(ce)，而萬用電表不(bu)是合法的(de)PD，PSE不(bu)會(hui)供(gong)電，無穩定電壓(ya)產(chan)生。
掌握了以上(shang)判斷方法，就能夠分辨出(chu)一(yi)臺PoE交換機是否標準(zhun)PoE供(gong)電了。
