With the second setup (10k from - to GND, to establisch a loose connection to earth) add a second 10k between the + and - input of the SCC ,
Didn't knew the powersupply was totally floating. The 10k between the inputs of the SCC will (should) do the job. On high level a current of 2.4 mA will flow but that's not problem for the sensor and resistor.