IP Library › Granted Patent US 7,499,170
Granted Patent B2
US 7,499,170 · App. 11/485,402 · Granted Mar 3, 2009

System and method for reading a test strip

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Quick Facts
Patent No.
US 7,499,170
App. No.
11/485,402
Granted
Mar 3, 2009
Kind
B2
Abstract

A system and method is disclosed which relates to reading test strips. The method may include reading and storing initial values of a front photodiode and a rear photodiode, reading current values of the front and rear photodiodes, detecting at least one change between initial and current values in the front or the rear photodiodes, comparing the detected value change of one of the photodiodes with the value of the other photodiode, and determining a condition of the test strip in response to the resulting comparison.

Claims (62)

1. A method of electronically reading a test strip, comprising:

illuminating two sections of the test strip using a light emitting diode;

reading and storing initial values of a front photodiode and a rear photodiode, each photodiode receiving reflected light from a different one of the two sections;

reading current values of the front and rear photodiodes;

calculating a ratio of the current value to the initial value for each of the front and rear photodiodes;

calculating a difference by subtracting the ratio of one of the photodiodes from the ratio of the other one of the photodiodes;

comparing the difference to a predetermined threshold; and

determining a condition of the test strip in response to the resulting comparison.

2. The method of claim 1 , wherein determining the condition of the test strip includes determining whether adequate fluid has reached the front photodiode.

3. The method of claim 1 , wherein determining the condition of the test strip includes determining whether adequate fluid has reached the rear photodiode.

4. The method of claim 3 , further comprising:

starting a timer for a predetermined period of time upon the determination that adequate fluid has reached the rear photodiode.

5. The method of claim 4 , further comprising:

reading final values of the front and rear photodiodes at the end of the predetermined period of time.

6. The method of claim 1 , wherein determining the condition of the test strip includes determining whether a line has appeared at the rear photodiode.

7. The method of claim 1 , wherein the comparing step includes calculating a result by multiplying the difference by a scale factor.

8. The method of claim 7 , wherein determining the condition includes comparing the result to a threshold value.

9. The method of claim 1 , further comprising:

comparing the values of the front and rear photodiodes with a low threshold and a high threshold to determine validity of the values.

10. A system of electronically reading a test strip, comprising:

means for illuminating a portion of the test strip using a light emitting diode, the portion including two spatially separated sections;

means for reading and storing initial values of a front photodiode and a rear photodiode, each photodiode receiving reflected light from a different one of the two sections;

means for reading current values of the front and rear photodiodes;

means for calculating a ratio of the current value to the initial value for each of the front and rear photodiodes;

means for calculating a difference by subtracting the ratio of one of the photodiodes from the ratio of the other one of the photodiodes;

means for comparing the difference to a predetermined threshold; and

means for determining a condition of the test strip in response to the resulting comparison.

11. The system of claim 10 , wherein means for determining the condition of the test strip includes means for determining whether adequate fluid has reached the front photodiode.

12. The system of claim 10 , wherein means for determining the condition of the test strip includes means for determining whether adequate fluid has reached the rear photodiode.

13. The system of claim 12 , further comprising:

means for starting a timer for a predetermined period of time upon the determination that adequate fluid has reached the rear photodiode.

14. The system of claim 13 , further comprising:

means for reading final values of the front and rear photodiodes at the end of the predetermined period of time.

15. The system of claim 10 , wherein means for determining the condition of the test strip includes means for determining whether a line has appeared at the rear photodiode.

16. The system of claim 10 , wherein means for comparing includes means for calculating a result by multiplying the difference by a scale factor.

17. The system of claim 16 , wherein means for determining the condition includes means for comparing the result to a threshold value.

18. The system of claim 10 , further comprising:

means for comparing the values of the front and rear photodiodes with a low threshold and a high threshold to determine validity of the values.

19. A method of electronically reading a test strip, comprising:

illuminating a portion of the test strip using a light emitting diode, the portion including two spatially separated sections;

reading and storing initial values of a front photodiode and a rear photodiode, each photodiode receiving reflected light from a different one of the two sections;

reading current values of the front and rear photodiodes;

calculating ratios of the initial and current values of the front and rear photodiodes;

starting a timer for a predetermined period of time when the result indicates adequate fluid has reached the rear photodiode;

reading final values of the front and rear photodiodes at the end of the predetermined period of time;

calculating a difference by subtracting the ratio of one of the photodiodes from the ratio of the other one of the photodiodes;

comparing the difference to a predetermined threshold; and

calculating a final result using the final and initial values of the front and rear photodiodes and in response to the resulting comparison.

20. The method of claim 19 , further comprising:

providing a power source to an electronic reading circuit.

21. The method of claim 20 , further comprising:

delaying for a predetermined delay time subsequent providing the power source and prior to reading the initial values.

22. The method of claim 19 , further comprising:

comparing the result to a threshold to determine whether adequate fluid has reached the front photodiode.

23. The method of claim 19 , further comprising:

comparing the result to a threshold to determine whether adequate fluid has reached the rear photodiode.

24. The method of claim 19 , further comprising:

comparing the final result to a threshold to determine a test result of the test strip.

25. The method of claim 19 , wherein the result is calculated using the following equation:

result=[(rear photodiode current value/rear photodiode initial value) −(front photodiode current value/front photodiode initial value)]*scaling factor.

26. The method of claim 19 , wherein the final result is calculated using the following equation:

final result=[(rear photodiode final value/rear photodiode initial value) −(front photodiode final value/front photodiode initial value)]*scaling factor.