PLC: UIS-WCB1
HMI: 10,4"
program: Unilogic 1.25.56
The Idea: We gonna supervise a valve (digital contact). If the valve is OPEN (NC digital contact) we are supervising it with 1 kOhm. If the valve is closed (digital contact open) we are supervising it with 2kOhm. We also want to supervise if the wiring is lost on its way to the valve or if the wiring is short circuit on its way to the valve this is to make an alarm if the cable is damaged or someone is trying to cut the cable.
Problem: First it worked if we simulated open and closed digital contact. We got a value when the contact was open, we got another value when the contact was closed and we also got a zero-value when we simulated that the cable was lost on its way to the digital contact(removed one wire from analog in). So far so good, but the problem occurs when we short circuit the cable on its way to the contact and it stalls to overflow (well it should be) but it wont release the overflow state when we reconnect it to the contact. It can now only show overflow status or zero-value if we remove one wire. It cannot show value open or close anymore.
