WO1992012416A1

WO1992012416A1 - Alcohol sensing device

Info

Publication number: WO1992012416A1
Application number: PCT/US1992/000332
Authority: WO
Original assignee: ALCOHOL SENSORS Inc
Current assignee: ALCOHOL SENSORS Inc
Priority date: 1991-01-11
Filing date: 1992-01-13
Publication date: 1992-07-23
Anticipated expiration: 1993-07-11
Also published as: AU1241392A

Abstract

An alcohol sensing method (fig. 1) and device (fig. 3) is adapted to prevent the operation of equipment, such as an automobile by a user in an alcohol-impaired state. The alcohol content of an initial breath sample is compared to a reference value to determine whether the alcohol level is below the acceptable maximum (8). The breath sample is also compared to a reference value representing non-alcohol containing breath to insure that a true breath sample is being offered (22). If both tests are passed, the equipment is activated (24). After activation breaths are requested on a periodic basis to insure that the alcohol level remains at an acceptable level (26, 38, 42). An alarm (70) is activated if either an invalid or a sample having an excessive alcohol level is sensed (36).

Description

ALCOHOL SENSING DEVICE The present invention relates to a new and improved method and apparatus for sensing the alcohol level of an operator of machinery, such as an automobile.

• 5 Background of the Invention

"* The cost, in personal injury and property damage, due to accidents involving intoxicated drivers is well documented and represents an unacceptable risk to the public. Accordingly, there have been numerous attempts to provide apparatus which is intended 0 to make a determination of the amount of alcohol consumed by an individual and thus the alcohol level of the blood. A common methodology employed in such apparatus is the use of a sensor adapted to measure the amount of alcohol in a breath sample passed across the sensor. Typically, the apparatus analyzes a breath 5 sample requested from the operator of the motor vehicle prior to engaging the ignition system. A sensor reading above a predetermined threshold, corresponding to an unacceptable alcohol level, locks out the ignition circuit and prevents starting of the vehicle. Such systems, while quite effective in preventing the starting of the vehicle upon the reception of an alcohol-tainted breath, are subject to a variety of shortcomings. For example, a driver fearing that his alcohol level would prevent automobile starting can fan ambient air across the sensor. In some systems this stratagem is overcome by providing a proximity sensor which

* requires close physical proximity between the user and the sensor and which would not be triggered by an inanimate object such as a fan.

Other methods for defeating such systems are not so easily counteracted. It is possible, for example, for the driver to utilize a surrogate, such as a passenger, to blow a non-alcohol-containing breath across the sensor, as the sensors normally are unable to differentiate between the driver's breath and that of a passenger or bystander. Once the ignition system is activated, the inebriated driver can operate the car without further risk of detection. Further, such systems do not prevent a non-inebriated driver from consuming alcohol while driving, thereby placing him or her in an inebriated state sufficient to fail the breath test, only after the initial test has been taken and passed. Accordingly, it is a purpose of the present invention to provide an alcohol monitoring system which has an increased resistance to being defeated or overridden.

A further purpose of the present invention is to provide a system which dif erentiates between breath and other vapor sources. Another purpose of the present invention is to provide a system which can detect changes in the alcohol level of a driver over a period of time.

A still further purpose of the present invention is to provide a system which requires sampling on a periodic basis to deter the ingestion of alcohol during vehicle operation. Brief Description of the Invention

In accordance with the above and further objects, the present invention comprises a gas and vapor sensor of the type adapted to provide an output signal proportional to the level of alcohol i a sensed sample. The sensor also is responsive to the gases and vapors which are present in the normal exhalation of an individual. A first breath sample is required prior to energization of the automobile ignition, whereby the characteristics of the sample are utilized to determine both whether the sample is consistent with a human breath and whether the alcohol level is above the prohibited cut-off point. The ignition cannot be started unless the sample meets both requirements.

Once activated by an initial breath meeting both requirements, the system operates in a passive mode, and continuously monitors the ambient air and compares the sensed alcohol level to the preset cutoff level. In addition, the system requires a breath sample on a periodic basis. Each time such a breath sample is required, the operator has a predetermined period of time in which to supply the sample to the sensor. Each requested breath sample is compared with the appropriate stored value to insure that a breath sample, rather than ambient air, is being sensed. In the event either an excessive level of alcohol is sensed at any time or it is determined that a proper breath sample has not been presented as requested, an alarm is activated. In a preferred embodiment, the alarm comprises intermittent operation of the vehicles lights, flashers and horn, so as to make the test failure conspicuous while not impairing normal operation of the vehicle. Brief Description of the Drawings

The fuller understanding of the present invention will be achieved upon consideration of the following detailed description of a preferred, but nonetheless, illustrative embodiment of the invention when taken in consideration with the annexed drawings, wherein:

FIG. 1 is a logical flow chart of the operation of the invention;

FIG. 2 is a graphical representation of typical sensor response; and

FIG. 3 is a schematic diagram of the operational circuitry for the invention. Detailed Description of a Preferred Embodiment

The present invention is based upon a relationship between the blood alcohol level of an individual and the amount of alcohol vapors appearing on the breath of the individual. In general, a blood alcohol level of approximately .08 - .10% is considered to define a level of intoxication sufficient for a charge of "DWI" or driving while under the influence of alcohol to be assessed against a driver. The purpose of the present invention is to compare the blood alcohol level to a value below this level, typically about .05%. Sensing is accomplished by a semiconductor element, preferably the TGS gas sensor presently marketed by Figaro Engineering Inc. of Osaka, Japan. The TGS sensor is a bulk semiconductor formed from^" sintered powdered tin dioxide.

The resistance between the active terminals of the TGS element decreases from a reference value established in ambient air in the presence of ethanol vapors, either alone or in combination with the other constituents of human breaths, while the vapor and gas content of exhaled human breath without an alcohol component drives the resistance of the sensor upward from its ambient level. This relationship, in both alcohol-containing and alcohol-free breath modify the resistance from that of ambient conditions in opposite senses is utilized by the present invention as a safeguard against false or improper samples. The sensor resistance is monitored by a microprocessor which compares the resistance to established levels and provides the necessary signals to request samples on a periodic basis.

As depicted in FIG. 2, as incorporated in the circuitry of the present invention the resistance for the sensor network in ambient air is approximately 9,500 ohms as indicated at area A. The typical composition of human breath without an alcohol component causes a resistance change to approximately 13,200 ohms, as shown in ^' area B, while the presence of alcohol on the breath corresponding to a blood alcohol level of approximately. .05 to .07% causes the sensor's network resistance to drop to approximately 6,000 ohms, as seen at area C. After the breath across the sensor is stopped, the resistance re-establishes itself at the ambient level at area D. Depending on the specific composition of the breath, the actual resistance may vary as illustrated. Experiments have established that, while the alcohol content of the breath will cause the sensor output to fluctuate below the ambient level on a generally proportional basis, alcohol-free breath consistently drives sensor resistance to the high 13 K ohm level. There thus exists a resistance band between 9.5 K and 13 K ohms which corresponds to a non-breath sample. This zone allows the system to distinguish between a breath and a simulated breath sample.

Operation of the sensing system of the present invention is depicted in FIG. 1. The sensor is in its initial, quiescent state at 10, the sensor network resistance being approximately 9,500 ohms. The automobile's ignition is turned on at 12, activating the system, preferably through the accessory switch portion of the ignition switch. The system includes a controlled switch, typically a relay or switched semiconductor, in series with the starter switch of the ignition system, preventing starting of the engine without breath processing by the system.

With the sensing system energized, a breath sample is requested at 14. Typically, this may be accomplished by activation of an indicator lamp, indicating to the driver that the system is awaiting a breath sample. The driver breathes across the sensor at 16, the sensor varying its resistance in response to the composition of the exhaled breath. The resistance of the sensor is then compared to the 6,000 ohm resistance level corresponding to the permissible alcohol limit at 18. If this alcohol level is equaled or exceeded, characterized by the sensor resistance being at or below 6,000 ohms, the ignition switch is not activated, the starter circuit remaining locked out at 20. This condition remains so long as the ignition switch is on. When the ignition switch is off, the sensor system is disabled and is reset. Turning on the

« 5 ignition again recommences the procedure, requiring another sample. * In addition to comparing the sensor output to the alcohol limit reference, the sensor output also is compared at 22 to the established ambient reference value of 9,500 ohms. Unless there is a deviation of sensor resistance, either upward to 13,200 ohms, 0 corresponding to alcohol-free breath, or downward to a point between 9,500 ohms and 6,000 ohms, corresponding to a breath sample having an alcohol component below the critical level, the system remains in the locked-out condition at 20. This prevents the use of an auxiliary "breath-creating" device, such as a fan, in an 5 attempt to trick the system into a false allowance.

If the breath sample is within the proper limits, the starter switch may be engaged at 24 and operation of the automobile is permitted. An indicator, such as a green light, may be simultaneously activated to indigate the receipt of a valid sample 0 and that the car may be started.

Once the initial breath is analyzed and passed, the system leaves the initial "lock-out" mode and commences the protective mode of operation, in which the receipt of an out-of-range sensor signal does not disable the ignition system, but rather causes the 5 operation of an auxiliary alarm to be activated. This phase commences at 26 where a timer is engaged to count down to a subsequent breath sampling request interval. Such breath sampling request intervals are intended to reoccur on a periodic basis during automobile operation with a preferred sequence being at 2, 5, 10, 15 and then repetitive 30-minute increments from ignition. The timer counts down at 28 until the sample interval is reached. At that time, a breath sample is requested at 30, at which time a request timer is activated. Once again, the sample request may be initiated by activating an appropriate indicator, such as a light or audio signal device. At the same time, request timer 32 is activated. In a preferred embodiment, the indicator requesting a sample may consist of a red light, such as a light-emitting diode, along with an audible indicator, preferably a semiconductor or piezoelectric oscillator. The request timer counts down at 34, and establishes the period in which a breath sample is to be received, the failure to receive a breath within the allotted time, preferably one minute, resulting in activation of the alarm at 36. The red light indicator is on for the entirety of the period. If no sample is received within the first 10 seconds, the audible indicator is also activated to create a more attention-getting condition.

The received breath again changes the resistance of the sensor, the sensor output being compared at 38 to the established alcohol limit and at 40 to the alcohol-free breath standard. If a high alcohol level is sensed, the alarm 36 is immediately activated. In addition, the breath must satisfy the validity test at 40. Until the validity test is passed, the request timer is not reset at 42. If a valid sample is not sensed within the interval, either because no breath was offered or because a spurious breath was provided, the alarm 36 is engaged. In a preferred embodiment, the alarm consists of a plurality of relay circuits activating the horn, high headlight beams, and flashers of the car in a pulse sequence on a continuous basis until the ignition is turned off. This mode of operation does not impair or affect the vehicle's performance or operation, thus allowing it to be operated under the control of the driver, while attracting attention and alerting the driver himself that system parameters have not been met.

If the breath sample received within the allotted time period has the acceptable characteristics, the sample request timer is reset for the next interval at 42 and the system commences again at 26, counting down the time to the next interval. In the interim, however, the sensor is not disabled. Rather, it continues to monitor the ambient atmosphere of the car interior. This function, depicted at 44, also causes an alarm output " at 48 whenever the alcohol limit is exceeded at 46. This further provides a backup and safeguard function.

The foregoing functions are preferably embodied within an electronic circuit comprising a microprocessor which has the capability of storing the appropriate values and controlling overall system function. This circuit is depicted generally in FIG. 3. As shown, the sensor 50 is coupled to the input of microprocessor 52, which is preferably a Motorola MC68705 or equivalent, through appropriate signal conditioning circuitry 54. Such microprocessor unit incorporates an integral analog to digital converter which allows the variable resistance output of the sensor network to be directly applied to the microprocessor input without external conversion circuitry. The sensor 50 itself is preferably the Figaro TGS unit having an integral heater which maintains the sensor element at an appropriate operating temperature. The microprocessor controls a series of logic output ports 54 through 60, each of which is coupled to an intended portion of the car circuitry, typically thought relays adapted to control the necessary current draw of the attached devices. Such outputs are to control the ignition, lights, flashers and horn as required. Output ports 62 and 64 are also utilized to provide signals to drive leds 66 and 68, which are used to indicate that a breath sample is desired (red) and that the sample sensed is acceptable (green). Output is also provided through port 66 for the piezoelectric sound generator 70. Timing signals for the system are generated internally by the microprocessor as regulated by crystal 72. The circuitry utilized is conventional and is apparent to those skilled in the art.

Using the appropriate criteria as discussed above, the microprocessor may be programmed in a manner known in the art to provide the timing and comparison functions. Such programming would typically include defining the 13,200, 9500 and 6000 ohm resistance levels for comparison to the sensor output. It is to be recognized that these values, and in particular the 6000 ohm value which corresponds to the alcohol level trigger point, may be varied as desired to modify the response of the unit. In general, programming is accomplished through application of an appropriate programming voltage to the programming pin (pin 7) of the microprocessor. This pin is kept at V_cc during normal operation.

Power for the system is derived from the automobile's battery; voltage regulator circuit 72 provides 5V power for the heater of sensor 48, while precision voltage regulator 74 provides the operating voltage for the microprocessor and associated circuitry. Both regulators are utilized in the manner known in the art. Regulator 74 may preferably be a TL 497AC unit.

In addition to the embodiment as discussed, it is possible to include an additional safeguard to the system. In particular, a proximity sensor may be employed to cause the rejection of a sample if the proximity sensor determines that an object is within a relatively small distance, in the order of two inches, from the breath sensor. This function would prevent, for example, the use of a balloon filled with exhaled, non-alcohol laden breath to generate a spurious breath sample. As the balloon would have to be closely directed at the gas sensor, the proximity sensor is utilized to deny allowance of any "breath" sample from a source within its sensing zone, thus requiring the balloon to be placed sufficiently far away from the gas sensor to prevent its effective direction against the sensor. This function can be embodied within steps 22 and 40 where the validity of a breath sample is determined.

Claims

WE CLAIM :

1. A method for monitoring the alcohol level of the operator of a piece of apparatus through the sensing of the alcohol level of the operator's breath by a sensor responsive to variations in

5 the composition of breath, comprising:

* establishing first, second and third sensor output reference values corresponding to ambient air, a baseline unacceptable breath alcohol level and alcohol-free breath, respectively; sensing a first breath to generate a first breath output; 0 comparing said first breath output to each of said reference values; generating a first output signal when said first breath output is either equal to said third output reference value or below said first and second output reference values; 5 activating the apparatus upon said first output signal; requesting additional breath samples on an interval basis and sensing each thereof to generate an interval breath output; and comparing each such interval breath outputs to each of said reference values to generate a second output signal if the criteria 0 for generating a first output signal are not met.

2. The method of claim 1, further including the step of setting a time interval for the receipt of each of said additional breath samples and generating said second output signal if a breath sample is not received within the time interval. __

3. The method of claim 2, wherein said step of generating a second output signal upon the non-receipt of a breath sample includes the step of comparing the output of said sensor to said third output reference value during said time interval.

4. The method of claim 2, wherein said second output signal is an aural and visual alarm.

5. The method of claim 4, wherein said apparatus is a motor vehicle and said output signal comprises intermittent activation of the lights and horn of^' the vehicle.

6. The method of claim 2, wherein said interval basis comprises sequential 2, 5, 10, 15 and then repetitive 30 minute intervals.

7. Apparatus for the monitoring of the alcohol content of the operator of a piece of equipment through the sensing of the alcohol level of the operator's breath, comprising: a sensor responsive to variations in the composition of breath; means for establishing first, second and third sensor output reference values corresponding to ambient air, a baseline breath alcohol level and alcohol-free breath, respectively; means for requesting a first and subsequent breath samples to be sensed by said sensor; means coupled to said sensor for comparing the output of said sensor to each of said reference values; means for generating a first output signal when said sensor output for said first breath sample is either equal to said third output reference value or between said first and second output values; means for activating the equipment upon receipt of said first output signal; and means for generating a second output signal if the criteria for generating a first output signal are not met upon comparison by said comparing means of said sensor output for one of said additional breath samples to said reference values.

8. The apparatus gf claim 7, wherein said second output signal generating means comprises aural and visual alarms.

9. The apparatus of claim 7, wherein said reference values are electrical resistances.

10. The apparatus of claim 7, wherein said comparison means is a microprocessor.

11. The apparatus of claim 7, wherein said means for requesting said subsequent breath samples comprise both aural and visual indicators.

12. The apparatus of claim 11, wherein said means for requesting said subsequent breath samples further comprise means to activate one of said indicators subsequent to the other.

13. The apparatus of claim 7, wherein said means for generating said second output signal further includes means for setting a time interval for receipt of each of said subsequent breath samples, a second output signal being generated if a breath sample meeting said first output signal criteria is not received during said time interval.