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預(yu)付(fu)費(fei)電(dian)(dian)(dian)能(neng)表(biao)(biao)(biao)又(you)稱購(gou)電(dian)(dian)(dian)式(shi)電(dian)(dian)(dian)能(neng)表(biao)(biao)(biao)，是一(yi)種用(yong)(yong)戶(hu)必(bi)須(xu)必(bi)須(xu)先買電(dian)(dian)(dian)才(cai)能(neng)用(yong)(yong)的(de)(de)(de)電(dian)(dian)(dian)能(neng)表(biao)(biao)(biao)。隨著(zhu)城網和(he)農(nong)網改造(zao)的(de)(de)(de)結束，電(dian)(dian)(dian)力用(yong)(yong)戶(hu)的(de)(de)(de)增加給抄表(biao)(biao)(biao)管(guan)理工(gong)作帶來(lai)了巨大(da)的(de)(de)(de)壓(ya)力，預(yu)付(fu)費(fei)電(dian)(dian)(dian)能(neng)表(biao)(biao)(biao)使用(yong)(yong)后，由于用(yong)(yong)電(dian)(dian)(dian)前已收回(hui)電(dian)(dian)(dian)費(fei)，可(ke)避免現場抄表(biao)(biao)(biao)，因此對一(yi)些電(dian)(dian)(dian)費(fei)回(hui)收困(kun)難的(de)(de)(de)用(yong)(yong)戶(hu)（包括一(yi)些人口流(liu)動大(da)的(de)(de)(de)用(yong)(yong)戶(hu)、邊遠分散用(yong)(yong)戶(hu)、經常欠費(fei)用(yong)(yong)戶(hu)和(he)臨時用(yong)(yong)戶(hu)）是非常適用(yong)(yong)的(de)(de)(de)。同時該電(dian)(dian)(dian)能(neng)表(biao)(biao)(biao)還可(ke)以(yi)實行功率限定。
電(dian)(dian)子式預(yu)(yu)付(fu)費電(dian)(dian)能(neng)表(biao)(biao)采(cai)用(yong)表(biao)(biao)內(nei)或(huo)表(biao)(biao)外加裝(zhuang)負荷控制(zhi)機構實現(xian)對用(yong)戶的用(yong)電(dian)(dian)控制(zhi)，以達到先(xian)付(fu)費后用(yong)電(dian)(dian)的目(mu)的，預(yu)(yu)付(fu)電(dian)(dian)能(neng)表(biao)(biao)內(nei)可以儲存電(dian)(dian)量或(huo)金額(e)，電(dian)(dian)量和金額(e)置入可采(cai)用(yong)IC卡等實物介質。
安裝該電(dian)(dian)(dian)(dian)能(neng)表的用(yong)戶可(ke)以到(dao)制定(ding)的售電(dian)(dian)(dian)(dian)部門（物(wu)業，房東(dong)等），將(jiang)購得的電(dian)(dian)(dian)(dian)量存(cun)入IC卡，當(dang)寫有儲存(cun)電(dian)(dian)(dian)(dian)量的IC卡插(cha)入預(yu)付費(fei)電(dian)(dian)(dian)(dian)能(neng)表時，電(dian)(dian)(dian)(dian)能(neng)表即可(ke)顯示購電(dian)(dian)(dian)(dian)數量。當(dang)電(dian)(dian)(dian)(dian)量將(jiang)要用(yong)盡時，電(dian)(dian)(dian)(dian)能(neng)表可(ke)預(yu)先(xian)發出斷電(dian)(dian)(dian)(dian)信號，從而控制斷電(dian)(dian)(dian)(dian)機構斷電(dian)(dian)(dian)(dian)。
一預付(fu)費電能(neng)表分(fen)類(lei)
（一(yi)）按工作原理分
（1）機(ji)電(dian)式預付費(fei)電(dian)能表
（2）全(quan)電子(zi)式預付費電能(neng)表
（二）按電能表的(de)準確度等級分
一般分為1.0級(ji)和2.0級(ji)表
（三）按被測相數分
（1）單相預付(fu)費電能表
（2）三相(xiang)（三相(xiang)三線或三相(xiang)四線）預付(fu)費電能(neng)表
; （四）按計收電(dian)價模式(shi)分
（1）單費(fei)率型
（2）多(duo)費率型
; （五）按負荷控制模式(shi)分(fen)
（1）表(biao)內置繼電器型
（2）表外置控制器型(xing)
二(er)電子式(shi)預付費電能表的特點
（1）不需要(yao)人工抄表(biao)，有利于(yu)現(xian)代(dai)化管理。隨著“一(yi)戶一(yi)表(biao)”的(de)實行，各物業單位管理的(de)電(dian)能(neng)表(biao)數(shu)量增(zeng)加，安裝預付費(fei)電(dian)能(neng)表(biao)后可避免人工抄表(biao)、上門(men)收費(fei)給用戶帶(dai)來的(de)諸(zhu)多不便，且歷(li)史購(gou)電(dian)數(shu)據(ju)均可以保存，便于(yu)用戶查(cha)詢。
（2）充分(fen)體現電力(li)的(de)(de)(de)商品屬性(xing)。預付(fu)費(fei)電能表按照商品屬性(xing)交換(huan)原則，實(shi)(shi)行(xing)先買點后用(yong)電，完全改革(ge)了傳統的(de)(de)(de)電費(fei)收取(qu)模(mo)式(shi)，充分(fen)體現了電力(li)的(de)(de)(de)商品屬性(xing)。用(yong)戶(hu)可以根據(ju)自己的(de)(de)(de)實(shi)(shi)際需要有計劃的(de)(de)(de)購電、用(yong)電，不會因欠費(fei)而產(chan)生滯納金，增加(jia)不必要的(de)(de)(de)開支。
（3）解決(jue)了收費(fei)難的問題(ti)。能很(hen)好地解決(jue)零(ling)散居(ju)民用(yong)(yong)戶、臨(lin)時用(yong)(yong)電用(yong)(yong)戶、經(jing)常欠費(fei)用(yong)(yong)戶的收費(fei)問題(ti)。
三(san)電(dian)(dian)子式(shi)預(yu)付費電(dian)(dian)能表工作原(yuan)理、結構組成及功能
由于采用IC卡的電(dian)(dian)子(zi)式預付費電(dian)(dian)表已經(jing)廣泛(fan)使用，現(xian)以IC卡電(dian)(dian)子(zi)式預付費電(dian)(dian)能(neng)表為例進行(xing)介紹。
（一）工作原理
微(wei)控制器(qi)通過(guo)對電(dian)(dian)能(neng)計(ji)量(liang)(liang)芯片(pian)輸出的電(dian)(dian)能(neng)采樣脈沖進(jin)行計(ji)算，進(jin)而轉(zhuan)化成電(dian)(dian)能(neng)量(liang)(liang)的處理，售電(dian)(dian)系(xi)統上(shang)的電(dian)(dian)量(liang)(liang)數(shu)據通過(guo)IC輸入到預(yu)付費電(dian)(dian)表內(nei)，表內(nei)微(wei)控制器(qi)進(jin)行電(dian)(dian)能(neng)計(ji)量(liang)(liang)、顯示、低電(dian)(dian)量(liang)(liang)報警(jing)和切(qie)斷或恢復用戶供電(dian)(dian)等操作。
用(yong)IC卡在物業或系統管(guan)理者那里購買一(yi)定數(shu)量(liang)(liang)(liang)(liang)(liang)的電(dian)(dian)(dian)(dian)(dian)(dian)量(liang)(liang)(liang)(liang)(liang)，此(ci)時IC卡中包含了電(dian)(dian)(dian)(dian)(dian)(dian)能(neng)表(biao)(biao)的密碼和所購電(dian)(dian)(dian)(dian)(dian)(dian)量(liang)(liang)(liang)(liang)(liang)，然后將IC卡插入預(yu)付費(fei)電(dian)(dian)(dian)(dian)(dian)(dian)表(biao)(biao)的卡座接口，讀寫系統就(jiu)可將這(zhe)些(xie)數(shu)據(ju)存入電(dian)(dian)(dian)(dian)(dian)(dian)能(neng)表(biao)(biao)單片機(ji)的存儲器中，并將表(biao)(biao)內剩余(yu)電(dian)(dian)(dian)(dian)(dian)(dian)量(liang)(liang)(liang)(liang)(liang)與新(xin)購電(dian)(dian)(dian)(dian)(dian)(dian)量(liang)(liang)(liang)(liang)(liang)進(jin)行(xing)代(dai)數(shu)相(xiang)加(jia)得到總電(dian)(dian)(dian)(dian)(dian)(dian)量(liang)(liang)(liang)(liang)(liang)，數(shu)據(ju)處理單元隨(sui)時將總電(dian)(dian)(dian)(dian)(dian)(dian)量(liang)(liang)(liang)(liang)(liang)與實際電(dian)(dian)(dian)(dian)(dian)(dian)量(liang)(liang)(liang)(liang)(liang)相(xiang)減，并顯示剩余(yu)電(dian)(dian)(dian)(dian)(dian)(dian)量(liang)(liang)(liang)(liang)(liang)。預(yu)付費(fei)電(dian)(dian)(dian)(dian)(dian)(dian)能(neng)表(biao)(biao)一(yi)般設(she)置(zhi)一(yi)個余(yu)額定值，當剩余(yu)電(dian)(dian)(dian)(dian)(dian)(dian)量(liang)(liang)(liang)(liang)(liang)等(deng)于此(ci)定值時，預(yu)付費(fei)電(dian)(dian)(dian)(dian)(dian)(dian)能(neng)表(biao)(biao)會發出警告(gao)信號(hao)，提醒用(yong)戶重(zhong)新(xin)購電(dian)(dian)(dian)(dian)(dian)(dian)，否則當電(dian)(dian)(dian)(dian)(dian)(dian)量(liang)(liang)(liang)(liang)(liang)用(yong)完，根據(ju)設(she)置(zhi)預(yu)付費(fei)電(dian)(dian)(dian)(dian)(dian)(dian)能(neng)表(biao)(biao)會斷開供電(dian)(dian)(dian)(dian)(dian)(dian)或繼續用(yong)電(dian)(dian)(dian)(dian)(dian)(dian)，如繼續用(yong)電(dian)(dian)(dian)(dian)(dian)(dian)，用(yong)電(dian)(dian)(dian)(dian)(dian)(dian)量(liang)(liang)(liang)(liang)(liang)記為賒欠電(dian)(dian)(dian)(dian)(dian)(dian)量(liang)(liang)(liang)(liang)(liang)。
一般在預付費電(dian)(dian)(dian)(dian)(dian)(dian)(dian)能(neng)表的(de)銘牌上(shang)裝有紅色功率(lv)指示燈(deng)用(yong)以提(ti)(ti)示用(yong)戶(hu)(hu)用(yong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)狀(zhuang)況(kuang)，用(yong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)負荷功率(lv)越(yue)大，該指示燈(deng)閃亮(liang)(liang)的(de)頻率(lv)越(yue)快，反之(zhi)越(yue)慢，當用(yong)戶(hu)(hu)不用(yong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)時，該指示燈(deng)可停在常亮(liang)(liang)或常滅狀(zhuang)態(tai)下，用(yong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)恢(hui)復后該等繼(ji)續隨(sui)用(yong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)負荷的(de)大小(xiao)而閃亮(liang)(liang)。用(yong)戶(hu)(hu)攜帶(dai)購(gou)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)卡到指定的(de)售(shou)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)管理人員那里購(gou)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)，將購(gou)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)后的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)卡插(cha)入預付費電(dian)(dian)(dian)(dian)(dian)(dian)(dian)能(neng)表，保存(cun)5秒后方可拔出(chu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)卡，用(yong)戶(hu)(hu)即可用(yong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)，當電(dian)(dian)(dian)(dian)(dian)(dian)(dian)能(neng)表的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)量(liang)(liang)(liang)(liang)接近報(bao)警(jing)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)量(liang)(liang)(liang)(liang)時，表上(shang)報(bao)警(jing)燈(deng)會(hui)閃亮(liang)(liang)，提(ti)(ti)醒(xing)用(yong)戶(hu)(hu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)量(liang)(liang)(liang)(liang)已剩不多(duo)了，當預付費電(dian)(dian)(dian)(dian)(dian)(dian)(dian)能(neng)表的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)量(liang)(liang)(liang)(liang)到達報(bao)警(jing)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)量(liang)(liang)(liang)(liang)時，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)能(neng)表會(hui)發出(chu)斷電(dian)(dian)(dian)(dian)(dian)(dian)(dian)報(bao)警(jing)，此時用(yong)戶(hu)(hu)將電(dian)(dian)(dian)(dian)(dian)(dian)(dian)卡重新插(cha)入表內一次，可繼(ji)續使用(yong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)量(liang)(liang)(liang)(liang)，此功能(neng)用(yong)于(yu)再次提(ti)(ti)醒(xing)用(yong)戶(hu)(hu)及時購(gou)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)。
（二）預(yu)付費功能
預付費(fei)電能表所需要(yao)的(de)功能因地(di)(di)而異(yi)，或根據不(bu)同地(di)(di)區的(de)技術條(tiao)件(jian)要(yao)求的(de)不(bu)同而不(bu)同一般有以下功能。
1數(shu)據(ju)預置功能
售電(dian)管理系統可(ke)通過用戶(hu)卡(ka)或專(zhuan)用設(she)置卡(ka)對預購電(dian)量、剩余報(bao)警電(dian)量門(men)限、最大囤積電(dian)量、負荷門(men)限及協議透支電(dian)量等參數進行設(she)置。
2疊加
輸入電(dian)(dian)(dian)能表的(de)本次購電(dian)(dian)(dian)量(liang)或(huo)購電(dian)(dian)(dian)金(jin)額，應能與(yu)電(dian)(dian)(dian)能表內的(de)剩余(yu)電(dian)(dian)(dian)量(liang)或(huo)剩余(yu)金(jin)額疊加(jia)。IC卡插(cha)電(dian)(dian)(dian)能表時(shi)，應有提示(shi)讀(du)出功(gong)能，包括回讀(du)。如操(cao)作成功(gong)顯示(shi)“成功(gong)”，否則顯示(shi)“失(shi)敗”。
3數據回讀功能
可通過用戶卡插卡抄表，將表內的總電(dian)(dian)量、剩余電(dian)(dian)量、總購電(dian)(dian)記錄等(deng)回(hui)寫到(dao)用戶IC卡中(zhong)，并以其作為(wei)媒(mei)介回(hui)傳至售電(dian)(dian)系統
4斷電控制功能
當預付費表內的剩余電(dian)量用盡(jin)(jin)或協議透(tou)支電(dian)量用盡(jin)(jin)時，電(dian)能表能直接輸出掉閘控制信號，切(qie)斷用戶的用電(dian)負荷，強制用戶購電(dian)，實現用戶“先買電(dian)后(hou)用電(dian)”
5剩(sheng)余電量報警功能
當(dang)電(dian)(dian)(dian)(dian)(dian)能(neng)(neng)表(biao)(biao)內(nei)(nei)的剩(sheng)(sheng)余(yu)(yu)電(dian)(dian)(dian)(dian)(dian)量(liang)小于或(huo)等于系統所設(she)置的“剩(sheng)(sheng)余(yu)(yu)報警電(dian)(dian)(dian)(dian)(dian)量(liang)”時，電(dian)(dian)(dian)(dian)(dian)能(neng)(neng)表(biao)(biao)發(fa)光報警，以提醒用戶(hu)，剩(sheng)(sheng)余(yu)(yu)電(dian)(dian)(dian)(dian)(dian)量(liang)報警時，電(dian)(dian)(dian)(dian)(dian)能(neng)(neng)表(biao)(biao)固定顯(xian)示(shi)(shi)表(biao)(biao)內(nei)(nei)“剩(sheng)(sheng)余(yu)(yu)報警電(dian)(dian)(dian)(dian)(dian)量(liang)”。用戶(hu)可插(cha)卡(ka)撤除報警信(xin)號輸出，電(dian)(dian)(dian)(dian)(dian)能(neng)(neng)表(biao)(biao)顯(xian)示(shi)(shi)可恢復正常循(xun)顯(xian)。
6協議(yi)透(tou)支功能(neng)
如果(guo)預(yu)付費(fei)電(dian)(dian)(dian)能表內置(zhi)的協議透支電(dian)(dian)(dian)量(liang)大(da)于零時，在剩余電(dian)(dian)(dian)量(liang)用(yong)(yong)盡(jin)時，用(yong)(yong)戶(hu)可以通(tong)過(guo)插卡撤除報(bao)警，直至預(yu)置(zhi)協議透支電(dian)(dian)(dian)量(liang)用(yong)(yong)盡(jin)，電(dian)(dian)(dian)能表切斷用(yong)(yong)戶(hu)，此(ci)時用(yong)(yong)戶(hu)必須輸入新的購電(dian)(dian)(dian)電(dian)(dian)(dian)量(liang)方可恢復用(yong)(yong)電(dian)(dian)(dian)。
7限制(zhi)囤積電量(liang)功能
可(ke)(ke)通過(guo)售電(dian)(dian)(dian)系統對電(dian)(dian)(dian)能(neng)表(biao)(biao)預置“囤(dun)(dun)積(ji)電(dian)(dian)(dian)量(liang)(liang)(liang)(liang)(liang)”，用戶的(de)(de)新購(gou)(gou)電(dian)(dian)(dian)量(liang)(liang)(liang)(liang)(liang)與表(biao)(biao)內(nei)的(de)(de)剩(sheng)余電(dian)(dian)(dian)量(liang)(liang)(liang)(liang)(liang)之和大于預置的(de)(de)“囤(dun)(dun)積(ji)電(dian)(dian)(dian)量(liang)(liang)(liang)(liang)(liang)”時，電(dian)(dian)(dian)能(neng)表(biao)(biao)拒(ju)絕接(jie)受卡中的(de)(de)新購(gou)(gou)電(dian)(dian)(dian)量(liang)(liang)(liang)(liang)(liang)，只有當電(dian)(dian)(dian)能(neng)表(biao)(biao)內(nei)的(de)(de)剩(sheng)余電(dian)(dian)(dian)量(liang)(liang)(liang)(liang)(liang)用至其與新購(gou)(gou)電(dian)(dian)(dian)量(liang)(liang)(liang)(liang)(liang)之和小于“囤(dun)(dun)積(ji)電(dian)(dian)(dian)量(liang)(liang)(liang)(liang)(liang)”時，用戶卡中的(de)(de)新購(gou)(gou)電(dian)(dian)(dian)量(liang)(liang)(liang)(liang)(liang)方可(ke)(ke)追加到表(biao)(biao)中。
8負電(dian)量記錄和自動扣除功(gong)能(neng)
在某(mou)種(zhong)情況下(xia)（如負(fu)荷開關故障(zhang)或預置的協議透支(zhi)電(dian)(dian)(dian)(dian)量(liang)(liang)(liang)大于(yu)零(ling)時(shi)(shi)），電(dian)(dian)(dian)(dian)能(neng)(neng)表內的剩(sheng)余電(dian)(dian)(dian)(dian)量(liang)(liang)(liang)為零(ling)后用戶(hu)仍繼續用電(dian)(dian)(dian)(dian)，此時(shi)(shi)電(dian)(dian)(dian)(dian)能(neng)(neng)表記錄負(fu)電(dian)(dian)(dian)(dian)量(liang)(liang)(liang)并提(ti)示(shi)符號(hao)、報警。若電(dian)(dian)(dian)(dian)能(neng)(neng)表表內有負(fu)電(dian)(dian)(dian)(dian)量(liang)(liang)(liang)，用戶(hu)再(zai)次(ci)購電(dian)(dian)(dian)(dian)時(shi)(shi)購電(dian)(dian)(dian)(dian)量(liang)(liang)(liang)必須大于(yu)欠費電(dian)(dian)(dian)(dian)量(liang)(liang)(liang)，購電(dian)(dian)(dian)(dian)插卡式電(dian)(dian)(dian)(dian)能(neng)(neng)表優先(xian)在新購電(dian)(dian)(dian)(dian)量(liang)(liang)(liang)中扣除負(fu)電(dian)(dian)(dian)(dian)量(liang)(liang)(liang)，經扣除后，剩(sheng)余電(dian)(dian)(dian)(dian)量(liang)(liang)(liang)大于(yu)零(ling)時(shi)(shi)方能(neng)(neng)合閘供電(dian)(dian)(dian)(dian)。
9負荷控制功能
當用(yong)戶(hu)(hu)負(fu)(fu)荷連續(xu)(xu)一定時(shi)間超過(guo)預置的負(fu)(fu)荷限(xian)制(zhi)電(dian)(dian)量(liang)時(shi)，電(dian)(dian)能表聲光報警，LCD顯示(shi)當前負(fu)(fu)荷，同時(shi)直接或輸出外接掉(diao)閘控制(zhi)信號，切斷用(yong)電(dian)(dian)負(fu)(fu)荷。當用(yong)戶(hu)(hu)負(fu)(fu)荷連續(xu)(xu)一定時(shi)間低于預置的負(fu)(fu)荷限(xian)制(zhi)電(dian)(dian)量(liang)后，電(dian)(dian)能表自動恢復供電(dian)(dian)。
10受檢功(gong)能(neng)
電(dian)(dian)(dian)能(neng)表應能(neng)接受售電(dian)(dian)(dian)管理(li)系統制作的(de)(de)購電(dian)(dian)(dian)卡、抄表卡、檢測卡的(de)(de)檢查(cha)，能(neng)將電(dian)(dian)(dian)能(neng)表當前狀態(tai)(tai)信(xin)息返寫至抄表卡，以(yi)便對(dui)其(qi)運(yun)行(xing)(xing)(xing)狀態(tai)(tai)進行(xing)(xing)(xing)檢查(cha)。該功(gong)能(neng)用于(yu)系統管理(li)者檢查(cha)現(xian)場(chang)運(yun)行(xing)(xing)(xing)的(de)(de)電(dian)(dian)(dian)能(neng)表狀態(tai)(tai)是(shi)否正常。
11補遺功能
當用(yong)戶售(shou)電(dian)(dian)卡(ka)(ka)遺(yi)失時，通過(guo)一定程序(xu)補遺(yi)，電(dian)(dian)能表也(ye)能接受新補售(shou)電(dian)(dian)卡(ka)(ka)，并拒(ju)絕原售(shou)電(dian)(dian)卡(ka)(ka)。
12辨偽功能
使(shi)用(yong)非(fei)指定介(jie)質時，電能(neng)表不應(ying)接受，并(bing)顯示相(xiang)應(ying)的(de)故障代碼提(ti)醒用(yong)戶。在(zai)撤(che)銷(xiao)非(fei)指定介(jie)質或非(fei)法操作后電能(neng)表應(ying)能(neng)正(zheng)常工作且數(shu)據不丟失。
13介質檢測功(gong)能
當介(jie)(jie)質（如電卡）或(huo)介(jie)(jie)質讀寫器（卡座）因受損而不能進行讀寫時(shi)，電能表顯示相(xiang)應的(de)故(gu)障代碼提醒用戶。
（四）防竊電功能(neng)
1防流失
全電(dian)(dian)(dian)子式(shi)電(dian)(dian)(dian)能(neng)表(biao)首(shou)先要對測(ce)量電(dian)(dian)(dian)路的(de)電(dian)(dian)(dian)壓和電(dian)(dian)(dian)流(liu)(liu)進行(xing)采樣才能(neng)進入乘法器。由于電(dian)(dian)(dian)流(liu)(liu)采樣電(dian)(dian)(dian)阻儀般(ban)小于2M歐，比機械表(biao)的(de)電(dian)(dian)(dian)流(liu)(liu)線(xian)(xian)圈(quan)內阻小得多，因此，在電(dian)(dian)(dian)能(neng)表(biao)外對電(dian)(dian)(dian)流(liu)(liu)通(tong)路用普通(tong)導線(xian)(xian)短接時，基(ji)本上不(bu)影響電(dian)(dian)(dian)子式(shi)電(dian)(dian)(dian)能(neng)表(biao)計(ji)量。
2防電流(liu)反向流(liu)入電流(liu)回(hui)路
當電(dian)流(liu)反(fan)(fan)向(xiang)流(liu)入(ru)機電(dian)式預付(fu)費電(dian)能表時，它像(xiang)機械表一樣(yang)反(fan)(fan)轉(zhuan)，但顯示(shi)的總電(dian)量并不減(jian)少。因光(guang)電(dian)采樣(yang)電(dian)路中接受轉(zhuan)盤反(fan)(fan)射光(guang)信號是沒有區(qu)別的，因此(ci)它仍然按(an)正轉(zhuan)情況計量。全(quan)電(dian)子(zi)式電(dian)能表也(ye)能防電(dian)流(liu)反(fan)(fan)向(xiang)流(liu)入(ru)電(dian)流(liu)回路引起電(dian)能表少計的情況。
3防(fang)假購電卡
購電卡的數據經算法加密，難以偽造，購一次(ci)電只能裝入一次(ci)。購電上有購電次(ci)數與(yu)裝入次(ci)數，單片機會判斷(duan)是(shi)否是(shi)假卡。
4防(fang)破壞IC卡表
為防止有人將IC卡(ka)卡(ka)座電(dian)源短(duan)路(lu)，損壞卡(ka)表(biao)，從而達(da)到竊電(dian)的目的，IC卡(ka)表(biao)設有卡(ka)座電(dian)源隔離電(dian)路(lu)，當卡(ka)座電(dian)源短(duan)路(lu)時(shi)，內部電(dian)源仍能(neng)(neng)正常工作，不影響電(dian)能(neng)(neng)計量。