Interference Detector and Methods

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.

What is claimed is: 
     
         1 . An interference detector for detecting electro-magnetic interference corrupting a signal from a breath alcohol sensor, the detector comprising a processor programmed to:
 receive the signal from the breath alcohol sensor;   differentiate the signal to generate a differentiated signal;   compare the differentiated signal to a predefined threshold for a time rate of change range; and   determine that an interference corrupting event is detected if the time rate of change is outside the respective predetermined range.   
     
     
         2 . The detector of  claim 1  wherein the processor is further programmed to discard the signal if the interference corrupting event is detected. 
     
     
         3 . The detector of  claim 1  wherein the processor is further programmed to determine a second order or higher order derivative of the signal. 
     
     
         4 . The detector of  claim 1  further comprising an analog-to-digital converter for converting the signal into a digital signal. 
     
     
         5 . The detector of  claim 1  wherein the differentiated signal has a slope and wherein the processor is programmed to compare the slope of the differentiated signal to a maximum allowable slope. 
     
     
         6 . The detector of  claim 5  wherein the interference corrupting event is detected if the slope is greater than the maximum allowable slope. 
     
     
         7 . The detector of  claim 6  wherein the processor is further programmed to discard the signal if the interference corrupting event is detected. 
     
     
         8 . An interference detector for detecting electro-magnetic interference corrupting a signal received from a breath alcohol sensor including a fuel cell, the detector comprising a processor programmed to:
 receive the signal from the breath alcohol sensor;   transform the signal from a time domain signal to a frequency domain signal; and   process the frequency domain signal to determine whether any frequency component present is outside a predefined range; and   determine that an interference corrupting event is detected if the frequency component present is outside the predefined range.   
     
     
         9 . The detector of  claim 8  wherein the processor is further programmed to discard the signal if the interference corrupting event is detected. 
     
     
         10 . The detector of  claim 8  wherein the processor is further programmed to determine a second order or higher order derivative of the signal. 
     
     
         11 . The detector of  claim 8  further comprising an analog-to-digital converter for converting the signal into a digital signal. 
     
     
         12 . The detector of  claim 8  wherein the frequency domain signal has a slope and wherein the processor is further programmed to compare the slope of the signal to a maximum allowable slope. 
     
     
         13 . The detector of  claim 12  wherein an interference event is detected if the slope is greater than the maximum allowable slope. 
     
     
         14 . The detector of  claim 13  wherein the processor is further programmed to discard the signal if the interference event is detected.