A respiration frequency detecting system is proposed based on respiratory inductive plethysmograph technology.When the bellyband of the system is tied to the waist of the subject

the abdomen volume change during respiration can cause the position motion of the permanent magnet embedded in the bellyband

and Hall sensor array can detect the position of the magnet

and then the process of Expiration and inspiration is determined.The sensor signal is analyzed and processed by MCU

and then the respiratory frequency is calculated.Experiments on 10 subjects are repeated

and the results are compared with those of the respiration detection equipment.Results indicate that the average accuracy of the designed system is above 95 %

which verifies the reliability of this system.The designed respiratory frequency detecting system can be applied to sleeping respiratory detecting instruments and slow-respiration hypertension therapeutic equipment

and so on.