Hi. In my home alarm panel, the door sensor circuits are each landed on a pair of screw terminals. Across the terminals I read 13.5vdc with nothing attached. Each door sensor circuit is a loop through a normally closed contact, with a 2200 ohm resistor on one end. Most of the pairs of terminals for the door sensors read ~5vdc when the door is closed, and ~12.5vdc when the door is opened.
Except for one of the sets of terminals. It reads around 13 volts with the door closed and very slightly higher, like 13.4v with the door open. I confirmed the resistor value, even jumpered a new resistor in its place. Why wouldn't 2200 ohms draw down the voltage in this one circuit the same as it does in the other ones?
Except for one of the sets of terminals. It reads around 13 volts with the door closed and very slightly higher, like 13.4v with the door open. I confirmed the resistor value, even jumpered a new resistor in its place. Why wouldn't 2200 ohms draw down the voltage in this one circuit the same as it does in the other ones?