INTERFERENCE DETECTOR AND METHODS

• US 20080030357A1
• Filed: 10/15/2007
• Published: 02/07/2008
• Est. Priority Date: 09/22/2003
• Status: Active Grant

• Current Assignee: Alcotek, Inc., Intoximeters, Inc.
• Original Assignee: Alcotek, Inc., Intoximeters, Inc.
• Inventors: Forrester, M., Sibley, Gary, Mitchell, John, Lueck, Keith
• Granted Patent: US 7,855,081 B2
• Time in Patent Office: Days
• US Class Current: 340/658
• CPC Class Codes: G01D 3/032 affecting incoming signal, e.g. by averaging; gating undesired signals
• CPC Class Codes: G01D 3/08 with provision for safeguarding the apparatus, e.g. against abnormal operation, against breakdown
• CPC Class Codes: G01N 33/007 Arrangements to check the analyser calibrating G01N33/0006
• CPC Class Codes: G01N 33/4972 Determining alcohol content for vehicle safety devices B60K28/06
• CPC Class Codes: Y10S 436/90 Breath testing
• CPC Class Codes: Y10T 436/204165 Ethanol

Abstract

Interference detector and methods for detecting interference in a signal are described. More specifically, in one aspect, a method for detecting interference in a signal is provided. The method comprises determining whether the signal has at least one of a time and a frequency characteristic that is outside a predefined range, and determining that an interference event has been detected if the signal has at least one of such characteristics.

Claims

1. A method for detecting interference in a signal, said method comprising:

receiving a sampled signal;

comparing the signal to a predetermined expected sensor signal range including at least one of a predetermined time rate of change range and a predetermined frequency range by comparing the signal to a predefined threshold; and

determining that an interference event has been detected if at least one of the time rate of change and the frequency of the signal is outside the respective predetermined range.

2. A method in accordance with claim 1 further comprising:

filtering the signal using a high-pass filter; and

comparing the high-pass filtered signal to a predefined threshold.

3. A method in accordance with claim 1 further comprising:

differentiating the signal; and

comparing the differentiated signal to a predefined threshold.

4. A method in accordance with claim 1 further comprising:

transforming the signal from a time domain signal to a frequency domain signal; and

processing the frequency domain signal to determine whether any frequency component present is outside a predefined range.

5. A method in accordance with claim 1 wherein determining whether the signal has at least one of a time and a frequency characteristic further comprises determining whether a signal representative of breath alcohol content has at least one of a time and frequency characteristic that is outside a predefined range.

6. A method in accordance with claim 1 wherein determining whether the signal has at least one of a time and a frequency characteristic further comprises determining whether a signal representative of at least one of ethanol content, CO2 content, temperature, pressure, breath flow, and position has at least one of a time and frequency characteristic that is outside a predefined range.

7. A method in accordance with claim 1 further comprising determining a second order or higher order derivative of the signal.

8. An interference detector for detecting interference in a signal, said detector comprising a processor programmed to:

process a signal representative of breath alcohol content to determine whether the signal has been corrupted by interference; and

determine whether the signal has at least one of a time characteristic and a frequency characteristic outside respective predefined ranges.

9. A detector in accordance with claim 8 further comprising:

an amplifier coupled to said processor for amplifying the signal representative of breath alcohol content; and

a first analog-to-digital converter for converting an analog signal from said amplifier to a digital signal.

10. A detector in accordance with claim 9 further comprising:

a high pass filter coupled to said amplifier; and

a second analog-to-digital converter for converting an analog signal from said filter to a digital signal, said high pass filter and second converter are connected in parallel with said first converter.

11. A detector in accordance with claim 10 wherein at least one of said first converter and said second converter is coupled to said processor.

12. A detector in accordance with claim 10 further comprising:

a high-pass filter coupled to said amplifier; and

a comparator coupled to said high-pass filter, said high-pass filter and said comparator are connected in parallel with said first converter, said processor is coupled to said comparator.

13. A detector in accordance with claim 12 wherein said processor is programmed to determine whether the signal representative of breath alcohol content has been corrupted by interference based on a signal received from said high-pass filter.

14. A detector in accordance with claim 8 wherein signals representative of breath alcohol content are differentiated, said processor is programmed to determine whether the signal representative of breath alcohol content has been corrupted by interference based on the differentiated signal.

15. A detector in accordance with claim 8 wherein said processor is further programmed to determine whether the signal has been corrupted by electro-magnetic interference.

16. A detector in accordance with claim 8 wherein said processor is programmed to determine a second order or higher order derivative of the signal in determining whether the signal has been corrupted by interference.

17. A method for detecting interference in a signal, said method comprising:

determining whether the signal is within a predetermined range, the predetermined range being at least one of an expected predetermined range of a time rate of change of the signal and an expected predetermined range of frequency of the signal; and

generating an output signal indicative of the signal being corrupted by interference if the signal is outside at least one of the predetermined ranges.

18. A method in accordance with claim 17 further comprising discarding the signal if the signal is corrupted by interference.

19. A method in accordance with claim 17 further comprising:

filtering the signal using a high-pass filter; and

comparing the high-pass filtered signal to a predefined threshold.

20. A method in accordance with claim 17 further comprising:

differentiating the signal; and

comparing the differentiated signal to a predefined threshold.