Calibration

 

System calibration is essential to ensure that the amount of oxygen delivered to the patient is exactly the prescribed amount.

 

The differential pressure flow sensor was placed in line with a mass flow controller (alicat scientific, tucson, AZ).  The mass flow controller delivered oxygen through the differential pressure sensor tubing at flow rates of 0, 2, 5, 8 and 10 liters per minute.  The subsequent pressure sensor output was recorded at each flow value.  Since the relationship between flow and pressure is parabolic, the square root was taken of the sensor output and the flow was plotted vs. the square root of the sensor output.  Linear interpolation was used to determine the relationship between the two parameters.  The results are shown to the right.

 

The flow sensor calibration is adequate for delivering precise amounts of oxygen.  Real time continuous monitoring of oxygen flow allows the system to ensure that the proper amount of oxygen reaches the patient (neither too much nor too little).