Patent ID: 7260996

Claim:
A pressure sensor for measuring an external stress comprising: a) a substrate having: i) a bottom surface; ii) a recess formed in the bottom surface of the substrate; and iii) a top surface having a first area and a second area, the first area is located directly above the recess and the second area is located around the first area; and b) an apparatus having a first resistor and a second resistor, the first resistor is located on the top surface of the substrate in the first area and the second resistor is located in the top surface of the substrate in the second area surrounding the first area, wherein, when the pressure sensor is exposed to the external stress, the first resistor measuring the external stress by varying a first oscillating signal input into a first end of the first resistor and outputting a varied first oscillating signal from a second end thereof, and the second resistor receiving an input second oscillating signal in a first end thereof and outputting an output second oscillating signal from a second end thereof, the input second oscillating signal and the output second oscillating signal are unaffected by the external force.