We have an opto-isolator diode connected to a contact closure to ground. When the contact is closed, the cathode reads 0V when measured to ground. When the contact is opened, will I measure a voltage that is close to 28V? I can't remember if that node is treated as a "floating" node or not.
simulate this circuit – Schematic created using CircuitLab
node is treated as a "floating" node.... which node are you referring to? .... please add a label to the node in the schematic \$\endgroup\$