Methods of detecting RF interference in breath ethanol testing

• US 7,855,081 B2
• Filed: 10/15/2007
• Issued: 12/21/2010
• Est. Priority Date: 09/22/2003
• Status: Active Grant

• Current Assignee: Alcotek, Inc., Intoximeters, Inc.
• Original Assignee: Alcotek, Inc., Intoximeters, Inc.
• Inventors: Sibley, Gary L., Forrester, M. Rankine, Lueck, Keith W., Mitchell, John
• Primary Examiner(s): ALEXANDER, LYLE
• Application Number:
  US11/872,541
• Publication Number:
  US 20080030357A1
• Time in Patent Office: 1,163 Days
• Field of Search: 436/132, 436/900, 422/84, 73/233, 600/532
• US Class Current: 436/132
• 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 electro-magnetic interference corrupting a signal from a breath alcohol sensor, said method comprising:

receiving the signal from the breath alcohol sensor;

differentiating the signal to generate a differentiated signal;

comparing the differentiated signal to a predefined threshold for a time rate of change range; and

determining that an interference corrupting event is detected if the time rate of change is outside the respective predetermined range.

3. A method in accordance with claim 1 further comprising discarding the signal if the interference corrupting event is detected.

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

5. A method in accordance with claim 1 further comprising converting the signal into a digital signal.

6. The method of claim 1 wherein the differentiated signal has a slope and wherein the comparing step includes comparing the slope of the differentiated signal to a maximum allowable slope.

7. The method of claim 6 wherein the interference corrupting event is detected if the slope is greater than the maximum allowable slope.

8. The method of claim 7 further comprising discarding the signal if the interference corrupting event is detected.

2. A method for detecting electro-magnetic interference corrupting a signal received from a breath alcohol sensor including a fuel cell, the method comprising:

receiving the signal from the breath alcohol sensor;

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; and

determining that an interference corrupting event is detected if the frequency component present is outside the predefined range.

9. A method in accordance with claim 2 further comprising discarding the signal if the interference corrupting event is detected.

10. A method in accordance with claim 2 further comprising determining a second order or higher order derivative of the signal.

11. A method in accordance with claim 2 further comprising converting the signal into a digital signal.

12. The method of claim 2 wherein the frequency domain signal has a slope and wherein the comparing step includes comparing the slope of the signal to a maximum allowable slope.

13. The method of claim 12 wherein an interference event is detected if the slope is greater than the maximum allowable slope.

14. The method of claim 13 further comprising discarding the signal if the interference event is detected.