System and method for air time remaining calculations in a self-contained breathing apparatus
First Claim
1. A method for accurately determining air time remaining in a self-contained breathing apparatus of the type including breathing gas contained under pressure in a breathing gas supply tank, the method comprising:
- determining a compensated gas supply metric for gas contained in the tank, the compensated gas supply metric being compensated for at least one non-linearity;
converting said compensated gas supply metric into a mass; and
calculating air time remaining on the basis of a mass of breathing gas contained in the tank.
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Accused Products
Abstract
A method and apparatus for accurately determining air time remaining in a self-contained breathing apparatus quantifies the effects of various non-linearities in order to define an accurate estimate of air time remaining within a gas supply tank. An analytical expression relates a mass equivalent to measured tank pressure through a power function. The system determines the rate of change of pressure with respect to time in order to determine numerical values for a rate of change of mass equivalent with respect to time, as well as the values of a set of constants relating mass equivalent to the pressure power function. A range of pressure:mass equivalent data pairs are produced which express the pressure/mass equivalent relationship over a range of specified mass equivalents. A function is curve fit to the data points in order to develop an expression which relates mass as a function of pressure directly or various pressure:mass equivalent data points are stored in a look-up table and, for any given measured pressure, a corresponding mass can be determined by simply consulting the table.
58 Citations
11 Claims
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1. A method for accurately determining air time remaining in a self-contained breathing apparatus of the type including breathing gas contained under pressure in a breathing gas supply tank, the method comprising:
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determining a compensated gas supply metric for gas contained in the tank, the compensated gas supply metric being compensated for at least one non-linearity;
converting said compensated gas supply metric into a mass; and
calculating air time remaining on the basis of a mass of breathing gas contained in the tank. - View Dependent Claims (2, 3, 4, 5, 6)
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7. In a self-contained breathing apparatus of the type including breathing gas contained under pressure in a breathing gas supply tank, a system for effecting accurate air time remaining determinations, comprising:
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sensor means for determining a pressure of a breathing gas within the supply tank;
processor means for converting a pressure into a mass of breathing gas in accordance with a non-linear equation; and
processor means for determining air time remaining on the basis of a mass of breathing gas contained in the tank. - View Dependent Claims (8, 9, 10, 11)
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Specification