Ned_Flanders
Member
I have a strange fault on a capacitive sensor which follows.
On a packaging machine, a capacitive sensor detects a moving belt that has metal rollers (I was rubber belts with metal rollers until 6 years ago). In the last day or so the sensor started to switch on when the belt had passed. The sensor was changed for a new one(Some damage to the face) but it still does it.
Suspecting a damaged cable somewhere, or floating 24v voltage levels it was supplied direct to/from the plc(Siemens S7) but it still randomly switches "On" after the belt has passed and sometimes before the belt has arrived!
You can run the belt in manual all day without the rest of the machine and it will not false trigger.
To prove a point we removed the sensor from the machine and had it dangling outside the machine in free air.
When the machine runs in auto the sensor output led switches on and off randomly - and the output lead is disconnected.
I wonder if anyone has experienced anything similar?
My thoughts are it should be an inductive sensor but the old one has worked correctly for the last 6 years!!!
On a packaging machine, a capacitive sensor detects a moving belt that has metal rollers (I was rubber belts with metal rollers until 6 years ago). In the last day or so the sensor started to switch on when the belt had passed. The sensor was changed for a new one(Some damage to the face) but it still does it.
Suspecting a damaged cable somewhere, or floating 24v voltage levels it was supplied direct to/from the plc(Siemens S7) but it still randomly switches "On" after the belt has passed and sometimes before the belt has arrived!
You can run the belt in manual all day without the rest of the machine and it will not false trigger.
To prove a point we removed the sensor from the machine and had it dangling outside the machine in free air.
When the machine runs in auto the sensor output led switches on and off randomly - and the output lead is disconnected.
I wonder if anyone has experienced anything similar?
My thoughts are it should be an inductive sensor but the old one has worked correctly for the last 6 years!!!