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ET 200 SP HA , DI 16x24VDC HA 1 , 2 Wire connection differences

1/11/2022 9:28 AM	Rate (0)
Raghu Kodi Experienced Member Joined: 5/3/2018 Last visit: 2/15/2025 Posts: 56 Rating: (0)	Hello, Can someone help me with the Technical difference of DI 16x24VDC HA 1 (6DL1131-6BH00-0PH1) wiring scheme of 1 wire and 2 wire. Please explain the advantages of 2 wire connection over 1 wire connection. (Are there any functionalities accessible only on 2- wire connection. thanks Attachment 2 wire 1 wire.pdf (615 Downloads)

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1/14/2022 4:52 PM	Rate (0)
danw Gold Expert Joined: 3/28/2010 Last visit: 9/5/2025 Posts: 1171 Rating: (220)	No one else has replied, so even though I'm an analog guy that only uses DI's once in blue moon (that means, rarely), I'll speculate. I'll speculate that the 2-wire uses the rack/DI card's (+) DC voltage connection, UVn, as the voltage source to the field switch. Coming from the rack's power supply, there is some some finite capacity and therefore some limitations on what it can supply to the rack's cards, but the power supply's 'return', (-), is at a known potential Althernatively it appears that the 1-wire connection uses an external 24Vdc power supply that can be as big and ugly as money can buy, and even redundant if you're into redundancy. But when you use an external power supply, you need to make sure that its return and the return for the DI are at the same potential.

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