Design and construction of control expiratory time adjustment display knob for the Bird Mark 7 ventilator

The objective of this research was to design and construct the control expiratory time adjustment display knob for the Bird Mark 7 ventilator. This research has adopted the principle of fluid mechanics and the principle of electronics. The designed and constructed control expiratory time adjustment display knob for the Bird Mark 7 ventilator was composed of 4 main parts: (1) the input part consists of pressure transducer, (2) the signal conditioner part composes of differential amplifier and voltage comparator, (3) the processing part consisting of MCS-51 P89V51RD2 microcontroller with C - language program and (4) the display part includes a liquid crystal display, which shows the duration of one cycle of breathing and the breathing rate. The results of functional testing compare with ventilator calibrator FLUKE VT - 30 found that the error of the average duration of a breathing cycle is equal to 1.36 percent and the average percentage error of the respiratory rate was 2 percent.