Ordinary hot-wire/hot-film method for spirography application

Although hot-wire/hot-film has lots of advantages, but some problems like flow direction detection, variation of temperature and ambient pressure and presence of dust particles in the vicinity of the sensor, cause errors in medical application measurement. This paper describes an innovative way for using ordinary hot-wire/hot-film method in spirography. The innovation includes an obstacle between two hot-film sensors and a procedure for data processing considering all hot-wire/hot-film problems. In addition a calibration syringe with definite volume is used to modify the calibration of spirometer under different working conditions.