1756-DHRIO/ABPLC模塊
通常是在總線上加偏置,當(dāng)總線空閑或開路時,利用偏置電阻將總線偏置在一個確定的狀態(tài)(差分電壓≥-200mV)。如圖13。將A上拉到地,B下拉到5V,電阻的典型值是1kΩ,具體數(shù)值隨電纜的電容變化而變化。
上述方法是比較經(jīng)典的方法,但它仍然不能解決總線短路時的問題,有些廠家將接收門限移到-200mV/-50mV,可解決這個問題。例如Maxim公司的MAX3080系列RS-485接口,不僅省去了外部偏置電阻,而且解決了總線短路情況下的失效保護問題
1756-DHRIO/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