Patent ID: 6651517
Filing Date: 2003-11-25
Classification: B67D,G01F

Abstract:
A fuel dispensing system comprising:a dual counter-rotating rotor turbine flow meter having a first rotor and a second rotor for determining the volume of fuel dispensed, the first rotor and the second rotor each having a plurality of rotor blades, the fuel dispensing system further comprising a point of sale display controller adapted to accept a first pulse input and a second pulse input from the dual rotor turbine flow meter and input from a temperature sensor, the first rotor and the second rotor operating at different speeds, the first rotor having a first sensor mounted proximate thereto, the second rotor having a second sensor mounted proximate thereto, the first sensor creating the first pulse input as one of the plurality of rotor blades of the first rotor passes the first sensor, the second sensor creating the second pulse input as one of the plurality of rotor blades of the second rotor passes the second sensor, a timer, a counter and a counter timer integrated into the point of sale display controller, the counter counting counts of the first pulse inputs and the second pulse inputs from the first sensor and the second sensor, the counter timer being used to determine a first sample period and a second timer period whereby said counts result in an integral number of first pulse inputs and the second pulse inputs, the counted first pulse input and the timer being used to determine the frequency fA of said first pulse input by the formula fA=(Counted first pulse inputs during the first timer periodâˆ’1)/[(Nt3âˆ’Nt1)/fcc] where fcc is the clock speed, Nt1 being the timer reading at the start of the first time period which initially is when a first pulse is received from either of the corresponding sensors and subsequently is Nt3 from the preceding time period, Nt3 being the timer reading at the end of the first timer period, the counted second pulse input and the timer being used to determine the frequency fB of said second pulse input by the formula fB=(Counted second pulse inputs during first timer periodâˆ’1)/[(Nt4âˆ’Nt2)/fcc], Nt2 being the timer reading at the start of the second timer period which initially is when a second pulse is received from the other of the two sensors and subsequently is Nt4 from the preceding time period, Nt4 being the timer reading at the end of the second timer period, the point of sale controller calculating the Roshko numbers for each rotor by the formulas, RoA=[fA/v1][1+3&agr;(T1âˆ’TR) and RoB=[fB/v1][1+3&agr;(T1âˆ’TR) where TR is a reference temperature and T1 is a temperature reading from the temperature sensor, and &agr;=linear coefficient of expansion of the fuel and meter material and v1 is the kinematic viscosity of the fuel at the temperature reading, the point of sale controller calculating the Strouhal numbers StA1 and StB1 from the following formulae, StA1=f(RoA) and StB1=f (RoA), and average flow rate q1 for a timer period being q1=(fA1+fB1)/[(StA1+StB1)*(1+3&agr;(T1âˆ’TR)] and the quantity of fuel Q1 dispensed during the timer period being Q1=q1 (Nt4âˆ’Nt1) and the total fuel QT dispensed being calculated by summing Q1 over all periods.