A media height detection system is used in connection with an inkjet printer. A filament is disposed above the process path and transverse to the process direction. A displacement sensor mounted adjacent the process path has a connecting member extending outward. The filament is attached to the connecting member and anchored to the printer. A transducer in the displacement sensor generates an electrical signal in response to a force on the filament. The filament contacts the lead edge of the sheet in the event of sheet curl in excess of a predetermined curl range. This will cause the force in the filament, which is conveyed to the displacement sensor to generate the signal. The print head can be elevated in response to the signal, so that the sheet does not impact the print heads, causing damage. Alternately, the sheet can be discarded.