Why a non-connected output on BMXSDO0802 in de-energized state can be measured at 19V ?

The main reason of the 19V measured on a non-connected output from BMXSDO0802 device is that some internal polarization resistance are set (with high impedance) in order the module is able to detect a cut wire on the line. The cut wire detection feature cannot be disabled, only the cut wire detection reporting can be disabled in Control-Expert software tool.
The 19V measured on the digital output with output de-energized is not an issue because the module does not and cannot deliver enough current to activate an actuator. The output is compliant with standard IEC61131-2. Per IEC61131-2, the module shall not deliver a current higher than 0.5mA when output is de-energized. It is the case for BMXSDO0802 module. If the leakage current is below 0.5 mA, the de-energized output is in de-energized state and is not able to activate any actuator input.

Udgivet til: Schneider Electric Danmark