GB2147099A - Gas analyser - Google Patents

Abstract

A breathalyser suitable for use in self-testing by individuals comprises a housing (10) containing a gas analyser for determining the alcohol content in gas supplied thereto; a gas inlet (20) to the analyser, accessible to a user from the exterior of the housing; actuation means (12) for preparing the analyser for receiving a gas sample to be analysed; and indicator (22, 24) means for indicating the measured alcohol content of a sample. The actuation means may be operable on insertion of a coin. A user may obtain a straw from dispenser (16) for insertion into inlet (20) for passage of exhaled air. <IMAGE>

Description

SPECIFICATION Gas analyser Field of Invention This invention relates to gas analysers and is concerned particularly with a breathalyser, for measuring the amount of alcohol in a person's breath on exhalation, the invention having as an object provision of a breathalyser suitable for use in self-testing by individuals.

The Invention According to the present invention there is provided a breathalyser comprising a housing containing a gas analyser for determining the alcohol content in gas supplied thereto; a gas inlet to the analyser, accessible to a user from the exterior of the housing; actuation means for preparing the analyser for receiving a gas sample to be analysed; and indicate means for indicating the measured alcohol content of a sample.

The actuation means conveniently include a coin-freed mechanism operable on introduc tion of appropriate coinage or tokens to pre pare the analyser for use.

The gas inlet may comprise a simple mouthpiece or the like, with associated valve means if appropriate. In the case of apparatus intended for public use, for reasons of hygi ene disposable mouthpieces are preferable provided. Thus, in one preferred embodiment, the gas inlet is adapted to receive one end of a straw or like tubular member. A supply of straws or the like is provided, either in a separate container or located within the hous ing. In the latter case, dispensing means are provided for dispensing a straw to a user, eg on introduction of appropriate coinage to the coin-freed mechanism. In this case, the hous ing conveniently also includes a receptacle for used straws.

The- indicator means may comprise display means, eg a digital LED display, for indicating the measured value of the alcohol content of a sample. Additionally or alternatively, the indi cator means may comprise an indicator for displaying whether the measured amount of alcohol is above or below a given preset limit, eg the prevailing legal limit. In this case, calibration means is preferable provided to enable a given machine to be adjusted to accommodate variations in the preset limit, eg for use in different countries where different legal limits prevail or follow changes in the law. For example, a green light may be pro vided which is illuminated to indicate that a user is below the preset limit, and/or a red light may be provided which is illuminated to indicate that the user is above the preset limit.

Any suitable gas analyser may be used, eg a conventional solid state gas sensor.

The housing is conveniently in the form of generally rectangular metal box, eg suitable for wall or shelf mounting or for free standing use. Instructions for use of the apparatus are conveniently displayed in a front panel of the housing.

One embodiment of breathalyser in accordance with the invention will now be discribed, by way of example, with reference to the accompanying Figures in which: Figure 1 illustrates the external appearance of a breathalyser in accordance with the present invention; and Figure 2 is a simplified block diagram illustrating the functioning of the breathalyser.

Detailed Description of the Drawing Referring to the drawings, the breathalyser illustrated in Fig. 1 comprises a metal housing 10 housing a solid state gas analyser (not shown). A front panel of the housing includes a coin slot 1 2 and coin return apperture 14. A straw dispensing aperture 1 6 is also located in the front panel, together with an information panel 1 8.

An inlet 20 is provided for receiving a straw for supplying exhaled air to the gas analyser.

The housing also includes an LED readout display 22 for displaying the measured alco hol content of gas supplied thereto, and a "don't drive" indicator light 24.

In use, a user introduces an appropriate coin or coins to slot 1 2 to be fed to a coinfreed mechanism (not shown) which actuates the apparatus for use. A straw is then supplied to the user via aperture 1 6. The user locates one end of the straw in inlet 22 and exhales to supply gas to the analyser. The user should exhale steadily until a reading appears in the adjacent display 22, indiciating the measured alcohol content of the user's breath. If the 'don't drive' indicator 24 is lit, then this indicates that the measured alcohol content is above a preset limit, eg prevailing legal limit, and the user should not drive.

However, if this indicator is not lit, then the user's measured breath alcohol content does not exceed the preset limit.

The construction and operation of the breathalyser is further explained by the following description of the block diagram of Fig. 2.

1. COIN COUNTER CIRCUIT: A counter is toggled by a relay once each time a coin is dropped. The counter is located inside the locked machine and enables the operator to determine the amount of money that the machine has taken in.

A monostabie multivibrator (IC-18) is used to generate a stable pulse output with each coin drop. This eliminates noise present on the switch which couid create a false count An octal counter (IC-l 7) is used to count the number of coins dropped with each cycle.

DIP Switch (SW1-1, 2, 3, and 4) is used to select the number of coins necessary to activate the machine. This is done by select ing the appropriate output of octal counter IC17.

2. INSERT COIN (END OF TEST) LATCH AND TIMER: Flip flops IC-25 A and B are preset until the circuit is activated by the coin counter circuit.

Both flip flops (IC-25 A and B) will be reset simultaneously. This will cause the circuit to check for a ready condition through IC4-D. If a ready condition is present, a timer (IC23-B) will activate for a period of approximately 2 seconds. This 2 seconds allows the reset circuit to clear any previous readings or voltage conditions present.

3. COIN CHANGER LAMP CIRCUIT: In between uses, the coin changer lamp and the amber "insert coin" LED will be flashing alternatively. This condition is caused by IC20-A receiving a ready condition on pin 1 and an end of test condition on pin 2. This allows nand gate IC-1 3-A to gate through a flash pulse constantly present on pin 2.

IC-22-A insures that flip flop IC25-B will be in the preset state before ailowing a flash (ready) condition.

4. EXHALE LATCH: Flip flop (IC1 6-A) will be triggered by timer IC-23B if the circuit is activated AND in a ready condition. The green "exhale into straw" LED will be illuminated. The machine will wait in this condition until a breath sample is received.

5. AIR SWITCH: An air pressure sensor is employed to allow the user time to insert the straw and prepare for a breath sample. It also ensures that the user is blowing hard enough to obtain a usable reading. When activated, the pressure sensor will activate the remainder of the operation sequence.

6. AIR PRESSURE TIMER: Timer IC24-B is triggered by the air switch when an acceptable breath sample is detected. There is a 5 second time delay from the beginning of the breath sample until the timer resets which will cause the OBSERVE LATCH (IC1 6-B) to set.

7. OBSERVE LATCH AND TIMER: Flip Flop FC1 6-B is clock to the set state 5 seconds after a breath sample is detected.

This will illuminate the red "OBSERVE" LED.

Timer IC24-A is triggered when flip flop ICi 6-B is set. The timer will reset after approximately 5 seconds and return flip flop IC25-B to a preset condition. The amber "insert coin" LED will now be illuminated and the resultant display reading will be flashing.

When flip flop IC25-B is preset, time IC23 A is triggered for 5 seconds. After 5 seconds, flip flop IC25-A will be returned to a set condition which will allow the amber "insert coin" LED and the coin drop lamp to flash if the machine has returned to a ready state.

8. FLASH OSCILLATOR: Gate array IC-12 is used as a low frequency oscillator. The frequency is determined by RC network C11 and R28. This is the basic flash oscillator used to flash the display, the "don't drive" indicator, and the "insert coin" indicators. It also provides the triggers for the reset circuit.

9. GAS SENSOR: A Figaro TGS-3 1 2 gas sensor is employed along with the ioad resistor VR-2 to detect gas level changes. This is a semiconductor type gas sensor which changes in conductivity when exposed to hydrocarbons.

10. READY CONTROL CIRCUIT: Operational amplifier IC-l 1-A is used to ensure that the gas sensor output is below approximately 900 mv before a ready condition is possible.

Operational amplifier IC-l 1-B is used to detect the point at which the gas sensor output level returns to within 60% of its original starting voltage after a test is completed.

The outputs of Amps IC-l 1-A and B are gated together using IC4-C so that both conditions A and B must be present before a ready indication is possible.

Operational amplifier IC9-A is used to monitor the gas sensor output and amplify the resultant level 60%.

Analog switch IC3-A receives the output from IC9.A and switches that output to it's output whenever IC4-C detects a ready state.

IC4-B is used to "disengage" the ready circuit whenever the machine is in the EXHALE mode.

RC network R24, R25, C8 and C9 are used to allow the gas sensor output to "float" to its "idle" voltages (this can change from building to building). Whenever a sudden rise occurs in the gas sensor output, the voltage reading on FC11-5 will remain relatively constant causing the ready circuit to disengage and "wait" for the gas sensor output voltage to again return to its starting voltage plus 60%.

This circuit alllows the machine to compensate for some atmospheric variations.

11. RESET CIRCUIT: Monostable multivibrator IC19 will be constantly triggering between operation cycles whenever the machine is ready for use. The resultant of output pulses will reset the analog voltage input from the gas sensor through IC3-B (analog switch). This will cause the visual reading on the machine to reset from its previous reading to .00 and stay reset until the next legitimate reading.

12. DC LOG AMP: The gas sensor output is coupled through C10 which allows the machine to measure only the change in voltage across the gas sensor.

Operational amplifier IC9-A is employed to set the initial turn on point of the analog amplifier.

Operational amplifier IC8-B is used in conjunction with R15 and R16 to cause a voltage reduction of gas sensor output. The reduced voltage remains proportional to the original gas sensor output.

Operational amplifier IC8-A is configured as a type of DC summing amplifier with a turn on point of approximately 2.0 Volts on the gas sensor output. The turn on point of IC8-A is determined by the voltage divider R7 and R8. All voltages produced by the gas sensor below 2.0 Volts will be coupled through R11.

When the voltage rises above 2.0 Volts, IC8-A will begin to amplify and the resultant increased gain will be coupled through R9. This circuit allows the machine to compensate for a non linear gas sensor output.

13. PEAK DETECTOR: Operational amplifier IC10 is used to detect significant rises in the gas sensor voltage output and pull a "hold" off of the analog to digital converter. The circuit will again reinstate a "hold" condition when the sensor voltage stops rising or begins to drop.

14. HOLD CONTROL GATES: This circuit is used to keep a "hold" condition on the digital readout except when a legitimate reading is being taken or a "reset" condition exists.

15. ANALOG TO DIGITAL CONVERTER: A hybrid integrated circuit is used to perform the dual function of processing the analog input voltage from the DC LOG AMP and converted in to 7 segment output signals for the DISPLAY.

16. DON'T DRIVE LAMP CIRCUIT: This circuit causes a "DON'T DRIVE" lamp to flash whenever a .1 condition or higher is detected through nand gate IC1 3-C.

17. DISPLAY: A two digit incandescent display is used to display the reading. Incandescent displays were chosen because their relative brightness and clarity when compared to typical LED readouts.

TTL non-inverting buffers IC5, IC6 and IC7 are used to provide the necessary current source for the incandescent displays.

18. DISPLAY ENABLE: This gating circuit enables and disables the incandescent displays at the appropriate times by supplying a voltage source through driver transistors 01.

19. - 3.3 VOLT GENERATOR: The clock signal generated by IC1 is used to generate - 3.3 volts through IC - 2, D1, D2, C4, and C5.

20. POWER SUPPLY: 2 and 5 volt sources are generated to create some isolation between the high current incandescent readouts and the CMOS circuitry.

Claims (15)

1. A breathalyser comprising a housing containing a gas analyser for determining the alcohol content in gas supplied thereto; a gas inlet to the analyser, accessible to a user from the exterior of the housing; actuation means for preparing the analyser for receiving a gas sample to be analysed; and indicator means for indicating the measured alcohol content of a sample.

2. A breathalyser according to claim 1, wherein the actuation means includes a coinfreed mechanism operable on introduction of appropriate coinage or tokens to prepare the analyser for use.

3. A breathalyser according to claim 1 or 2, wherein the gas inlet comprises a mouthpiece, with associated valve means.

4. A breathalyser according to claim 1 or 2, wherein the gas inlet is adapted to receive one end of a straw or like tubular member.

5. A breathalyser according to claim 4, wherein a supply of straws is provided, either in a separate container or located within the housing.

6. A breathalyser according to claim 5, further comprising dispensing means for dispensing a straw to a user.

7. A breathalyser according to claim 4, 5 or 6, wherein the housing includes a receptacle for used straws.

8. A breathalyser according to any one of the preceding claims, wherein the indicator means comprises display means for indicating the measured value of the alcohol content of a sample.

9. A breathalyser according to any one of the preceding claims, wherein the indicator means comprises an indicator for displaying whether the measured amount of alcohol is above or below a given preset limit.

10. A breathalyser according to claim 9, further comprising calibration means to enable adjustment of the value of the preset limit.

11. A breathalyser according to claim 9 or 10, wherein a green light is provided which is adapted to be illuminated to indicate that a user is below the preset limit, and/or a red light is provided which is adapted to be illuminated to indicate that the user is above the preset limit.

1 2. A breathalyser according to any one of the preceding claims, wherein the gas analyser is a solid state gas sensor.

1 3. A breathalyser according to any one of the preceding claims, wherein the housing is in the form of generally rectangular metal box.

14. A breathalyser according to claim 13, wherein instructions for use of the apparatus are displayed on a front panel of the housing.

15. A breathalyser substantially as herein described with reference to, and as shown in, the accompanying drawings.