1756-DPALEN/ABPLC模塊
一般終端匹配采用終接電阻方法,前文已有提及,RS-422在總線電纜的遠(yuǎn)端并接電阻,RS-485則應(yīng)在總線電纜的開始和末端都需并接終接電阻。終接電阻一般在RS-422網(wǎng)絡(luò)中取100Ω,在RS-485網(wǎng)絡(luò)中取120Ω。相當(dāng)于電纜特性阻抗的電阻,因?yàn)榇蠖鄶?shù)雙絞線電纜特性阻抗大約在100~120Ω。這種匹配方法簡(jiǎn)單有效,但有一個(gè)缺點(diǎn),匹配電阻要消耗較大功率,對(duì)于功耗限制比較嚴(yán)格的系統(tǒng)不太適合。
另外一種比較省電的匹配方式是RC匹配,如圖9。利用一只電容C隔斷直流成分可以節(jié)省大部分功率。但電容C的取值是個(gè)難點(diǎn),需要在功耗和匹配質(zhì)量間進(jìn)行折衷。
1756-DPALEN/ABPLC模塊
1756
MFR. PART NUMBER DESCRIPTION
1756-A10 10 SLOT CONTROLLOGIX CHASSIS
1756-A13 13 SLOT CONTROLLOGIC CHASSIS
1756-A17 CHASSIS 17 SLOT CONTROLLOGIX
1756-A4 4 SLOT CONTROLLOGIX CHASIS
1756-A7 7 SLOT CONTROLLOGIX CHASSIS
1756-BA1 LOGIX5000 BATTERY ASSEMBLY
1756-CFM 2 CHANNEL /2 OUT CONFIGURABLE FLOWMETER
1756-CNB CONTROLNET BRIDGE MODULE
1756-CNBR CONTROLNET REDUNDANT BRIDGE MODULE
1756-CP3 LOGIX5000 RS232 PROGRAMMER CABLE
1756-DHRIO 2 CHANNEL DH+ AND/OR RIO SCANNER
1756-DNB DEVICE NET BRIDGE/SCANNER MODULE
1756-DPALEN CONTROLLOGIC SYSTEM DOCUMENTATION SET PRINTED
1756-ENET ETHERNET/IP BRIDGE MODULE
1756-GTWY CONTROLLOGIC GATEWAY CONFIGURATION SOFTWARE
1756-GTWYR SUPT REINSTATEMENT CONTRACT FOR 1756GTWY
1756-GTWYS SUPT RENEWAL CONTRACT FOR 1756GTWY
1756-HSC 2 CHANNEL /4 OUTPUT HIGH SPEED COUNTER
1756-IA16 79-132 VAC INPUT 16PTS
1756-IA16I 79-132 VAC ISOLATED INPUT 16PTS
1756-IA8D VAC DIAGNOSTIC INPUT 8PTS
1756-IB16 VDC INPUT 16PTS
1756-IB16D VDC DIAGNOSTIC INPUT
1756-IB16I VDC ISLOTED INPUT 16PTS