Fuel dispenser flow meter sensor fraud prevention

1. A method for detecting fraud caused by tampering with a fuel flow meter, comprising the steps of:

providing a fuel flow meter for measuring the flow of liquid fuel, said flow meter having at least one shaft supporting a rotor;

providing said flow meter with a rotary displacement sensor;

recording data indicative of a first angular position of said shaft upon termination of a first fueling transaction;

recording data indicative of a second angular position of said shaft upon initiation of a second fueling transaction; and

comparing data indicative of said first and second shaft angular positions to determine whether a difference exists.

2. The method of claim 1 , further comprising receiving a signal indicative of the termination of said first fueling transaction.

3. The method of claim 2 , further comprising receiving a signal indicative of the initiation of said second fueling transaction.

4. The method of claim 1 , further comprising storing data indicative of said first angular position and said second angular position in a memory associated with said rotary displacement sensor.

5. The method of claim 1 , wherein said rotary displacement sensor comprises an absolute sensor.

6. The method of claim 1 , wherein said rotary displacement sensor comprises a magnetic displacement sensor.

7. The method of claim 1 , wherein said rotary displacement sensor is an optical encoder.

8. The method of claim 1 , further comprising recording data indicative of a third angular position of said shaft after power is applied to a fuel dispenser after an outage.

9. The method of claim 1 , further comprising terminating said second fueling transaction if said data indicative of said first shaft angular position is not equal to said data indicative of said second shaft angular position.

10. A fuel flow meter, comprising:

a shaft supporting at least one rotor;

a rotary displacement sensor comprising at least one sensing element, a processor, and memory;

said displacement sensor adapted to store first data indicative of an angular position of said shaft in said memory upon termination of a first fueling transaction;

said displacement sensor further adapted to generate second data indicative of an angular position of said shaft upon initiation of a second fueling transaction;

said processor adapted to compare said first and second data to determine whether fa difference exists.

11. A fuel flow meter as in claim 10 , wherein said sensing element is selected from the group consisting of a magnetoresistive encoder, a hall effect encoder, an inductive encoder, a magnetic encoder, and an optical encoder.

12. A fuel flow meter as in claim 10 , wherein said displacement sensor further comprises an encoder shaft coupled to said flow meter shaft.

13. A fuel flow meter as in claim 12 , wherein removal of said displacement sensor from said flow meter causes one of said encoder shaft and said flow meter shaft to rotate relative to the other of said encoder shaft and said flow meter shaft.

14. A fuel dispenser, comprising:

a control system having control system memory;

internal fuel flow piping adapted for connection to a fuel flow path from a bulk storage tank to a nozzle;

a fuel flow meter having a shaft, said fuel flow meter located along said piping;

a rotary displacement sensor coupled to said fuel flow meter and in communication with said control system, said displacement sensor comprising displacement sensor memory;

wherein said displacement sensor is adapted to determine data indicative of the angular position of said shaft; and

wherein the data indicative of said angular position is stored in both said control system memory and said displacement sensor memory.

15. The fuel dispenser of claim 14 , wherein said displacement sensor is adapted to determine data indicative of the angular position of said shaft at least upon termination of a first fueling transaction and upon initiation of a second fueling transaction.

16. The fuel dispenser of claim 15 , wherein at least one of said fuel dispenser control system and said displacement sensor compares the data indicative of said shaft angular positions to determine whether a difference exists.

17. The fuel dispenser of claim 16 , wherein both of said fuel dispenser control system and said displacement sensor compare said data indicative of said shaft angular positions to determine whether fraud has occurred.

18. The fuel dispenser of claim 16 , wherein said fuel dispenser is disabled if said data indicative of said shaft angular position upon termination of said first fueling transaction is not equal to said data indicative of said shaft angular position upon initiation of said second fueling transaction.

19. The fuel dispenser of claim 15 , wherein said fuel dispenser control system compares data indicative of said shaft angular position upon termination of said first fueling transaction stored in said control system memory to data indicative of said shaft angular position upon termination of said first fueling transaction stored in said displacement sensor memory to determine whether fraud has occurred.

20. The fuel dispenser of claim 14 , wherein said displacement sensor is adapted to determine data indicative of the angular position of said shaft when power is applied to said fuel dispenser after an outage.

21. A fuel flow meter, comprising:

a shaft supporting at least one rotor;

a rotary displacement sensor comprising a processor and memory;

said displacement sensor comprising an optical encoder adapted to output an expected number of position signals per revolution of said shaft and one or more reference signals per revolution of said shaft;

said displacement sensor adapted to store data indicative of said position signals and said one or more reference signals in memory;

said displacement sensor adapted to compare a first number of position signals received after receiving a reference signal before termination of a first fueling transaction and a second number of position signals received after initiation of a second fueling transaction to said expected number of position signals to determine whether fraud has occurred.

22. The fuel flow meter of claim 21 , wherein said second fueling transaction is terminated if said second number of position signals, when subtracted from said expected number of position signals, is not within one of said first number of position signals.

23. The fuel flow meter of claim 21 , wherein said optical encoder comprises a shaft-mounted disc.

24. The fuel flow meter of claim 21 , wherein said optical encoder is an absolute encoder.

25. A method for detecting fraud caused by tampering with a fuel flow meter, comprising the steps of:

providing a fuel flow meter for measuring the flow of liquid fuel, said flow meter having a housing and at least one shaft supporting a rotor;

providing said flow meter with a rotary displacement sensor having a housing and a shaft; and

providing a first coupling between said flow meter shaft and said rotary displacement sensor shaft;

wherein said first coupling is operative to cause one of said rotary displacement sensor shaft and said flow meter shaft to rotate relative to the other of said rotary displacement sensor shaft and said flow meter shaft upon removal of said rotary displacement sensor from said flow meter housing.

26. The method of claim 25 , further comprising providing a second coupling between said flow meter housing and said rotary displacement sensor housing.

27. The method of claim 26 , wherein said second coupling prevents rotation of said rotary displacement sensor housing relative to said flow meter housing upon removal of said rotary displacement sensor from said flow meter housing.

28. The method of claim 26 , wherein said second coupling comprises a socket defined in said flow meter housing adapted to receive a protrusion of said displacement sensor housing.

29. The method of claim 26 , wherein said second coupling prevents access to said flow meter shaft and said rotary displacement sensor shaft when said flow meter housing is coupled with said rotary displacement sensor housing.

30. The method of claim 25 , wherein said first coupling comprises at least one pin on one of said displacement sensor shaft and said flow meter shaft configured to engage with at least one slot on the other of said rotary displacement sensor shaft and said flow meter shaft.

31. The method of claim 30 , wherein said at least one slot is helical.

32. The method of claim 25 , wherein said first coupling comprises a one-way clutch.