Owls boss Paul Sturrock was at last night’s 4-2 reserve victory against Wigan and moved quickly to snap up the 24-year-old Dane in a temporary deal.
Bischoff goes straight into a relegation battle as Wednesday are two points above the drop zone in the Championship and he has been named in the squad for their home game with QPR on Saturday.
Bischoff enjoyed two successful loan periods in the Championship with Wolves last season, while City keeper Nicky Weaver was on loan at Wednesday earlier this season.