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SIMATIC S7-300 / S7-300F

DI module signal level

Thread Starter: SKG   Started: 7/19/2012 6:03 AM   Replies: 1

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  7/19/2012, 6:03 AM
SKG
Joined 5/30/2008
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Dear all,

1. In the manual, it has been stated for the digital module 321-1bl00-0aa0 that "1" signal is 13 V to 30 V and "0" signal -30 V to 5 V. Does it mean that when voltage of any digital input address (say for example I 0.0) with respect M is 13 V to 30 V, the logic will be "1" and when the voltage level of the address is between -30 V to +5 V, the logic will be "0"?

2. Then, what will be the logic, if the address is discoonected from any source?

3. Practically it has been found to acheive "0" logic when the address is disconnected from the source. Then, what is the difference between the input disconnected from source and the input is at voltage level -30 V to +5 V?

I would be thankful if anybody make it clear to me.

Regards,

SKG
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  7/20/2012, 7:34 PM
Rockon
Joined 11/2/2008
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Ans 1: Your assumption is right.(0 If values mentioned by you are defined in manual I have never checked at such micro level. But there may exist some tolerance i.e. at  13V 

Ans 2: When address is disconnected logic will be zero

Ans 3: As DI works on voltage difference. There will be no difference between disconnected (means 0V)and voltage between -30V to 13V. If you want to have any error on disconnection you can go for special modules with diagnostic (wire break) capabilities.
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