The physical mechanism of the anisotropic magnetoresistive sensor HMC1002 is introduced

the measuring mechanism and its signal processing circuit are described.When a vehicle is moving over the detector

the surrounding magnetic field changes due to vehicle disturbance

and the output of the AMR sensor changes accordingly.The state of the vehicle can be judged based on the AMR sensor’s output

the sensor characteristic is tested:when the vehicle detected is moving over the detector along different directions（south-north）

the output changes are different;and when the vehicle detected is moving over the detector along different speed

the output changes also are different

the result shows that this detector can realize vehicle detection.