EOL Resistor with 1756-IB16D Input Card?

Hi,
Could anyone please explain how EOL(End of line) resistor works with 1756-IB16D Card to detect Open wire fault??

Do you mean "leakage resistor"? If so see picture below from manual.

How does the leakage Resistor work though?

The "leakage resistor" is connected across an open contact, such as a push-botton etc., and will cause a small amount of current into the PLC input when the contact is open.

The input card has circuitry to detect this current as a minimum. If a field wire drops off, or is cut etc., then the input card receives no input current, and the card signals a "wire-off" fault.

How about when the open contact is closed?

[email protected] said:

How about when the open contact is closed?

Click to expand...

Then the input card works normally.

Basically, they're using the resistor to be able to generate a third state for a digital input.

High Current (contact closed) = Input On
Low Current (contact open) = Input Off
No Current = Wire break fault