This paper presents an investigation into improved, direct Salmonella detection on food contact surfaces using a double-layer planar coil detector and wireless phage-based magnetoelastic (ME) biosensors. Comparing with the single-layer coil detectors used in our previous research, double-layer coils with appropriate designs allow for better magnetic excitation of the biosensor and sensitivity of detection. In this way, a longer stand-off distance (distance between the sensor and detector), which may be necessary for testing surfaces with large roughness and curvatures, can be achieved. In addition, smaller biosensors (e.g., sub-millimeter long) with higher mass sensitivity can also be measured with this sensitive double-layer coil detector. Standard microelectronic fabrication techniques (photolithography, electroplating, etching and sputtering) were used to fabricate double-layer coils with various design parameters, including the thickness of layers, width, height, and spacing of coil turns. Both theoretical calculations and experimental data showed that the above coil geometric parameters have large effects on the signal amplitude, stand-off distance and detection sensitivity. Finally, with the newly fabricated double-layer coil detector, detection of Salmonella on a food-grade, ultra-high-molecular-weight polyethylene (UHMW-PE) surface was demonstrated. Multiple biosensors were measured simultaneously with a longer detection distance (> 1 mm). This double-layer scanning coil detector therefore facilitates the detection of pathogens on food and food contact surfaces.