Patent GB-1468619-A (GB)
Title: Exhalation inspecting apparatus
IPC: G01N33/497
Filed: 1975-06-11
Abstract: 1468619 An exhalation inspecting apparatus NISSAN MOTOR CO Ltd 11 June 1975 [18 June 1974] 24996/75 Heading G1N An exhalation inspecting apparatus comprises power supply means 24, an alcohol level detecting circuit 26 connected to the power supply means 24 by a first set of wires 14a, 14b and operative to produce a first output voltage V 1  indicative of an alcohol concentration of air exhaled by a subject  and a second output voltage V 2  indicative of the volume of the subject's exhaled air, a discriminating circuit 30 connected to said alcohol level detecting circuit 26 by a second set of wires 14c, 14d and operative to produce a first output signal R 1  if said first output voltage V 1  is indicative of an alcohol concentration lower than a predetermined allowable limit and said second output voltage V 2  is indicative of a volume of exhaled air larger than a predetermined minimum limit and a second output signal R 2  if said first output voltage V 1  is indicative of an alcohol concentration higher than said allowable limit and/or said second output voltage V2 is indicative of a volume of exhaled air smaller than said minimum limit. A wire breakage detecting circuit 28 responsive to breakage of any one of said wires is provided and is operative to produce a first output signal S 1  in the absence of breakage in said wires 14a to 14d and a second output signal S 2  in response to breakage of at least one of said wires. A control circuit 32 is responsive to the signals from said discriminating circuit 30 and said wire breakage detecting circuit 28 for producing a first output signal T 1  in the presence of both of the first output signals R 1 , S 1  from the discriminating circuit and the wire breakage detecting circuit and a second output signal T 2  in the presence of at least one of the second output signals R 2 , S 2  from the discriminating circuit and the wire breakage detecting circuit. The discriminating circuit 30 comprises a pair of comparator circuits 66, 68, circuit 66 processing the first output voltage V 1  and circuit 68 the second output voltage. Said predetermined allowable limit of alcohol concentration is defined by a voltage E 1  impressed on an input of comparator circuit 66 and said predetermined minimum limit of air volume is defined by a voltage E2 impressed on an input of the comparator circuit 68. The circuits 66 and 68 are such that the circuit 66 gives a logic 1 output when the voltage V 1  is above the allowable limit and circuit 66 gives a logic 1 output when the voltage V 2  is below the minimum limit. The alcohol level detecting circuit 26 is housed within a blow-in tube Fig. 1 (not shown) and comprises, for detecting the alcohol level, a unit 50 consisting of an alcohol-sensitive element 50a the resistance of which is reduced when heated and subjected to alcoholic atmosphere and a heating element 50b for heating the element 50a, and for detecting the air volume, thermistors 54, 56. The wire breakage detecting circuit comprises a pair of switches in the form of transistors 86, 88, transistor 86 being associated with wires 14a and 14c and transistor 88 with wires 14b and 14d. The transistors 86, 88 conduct when the wires are unbroken but cease conduction on an associated wire breaking. The alcohol level detecting circuit 26 is also connected to earth through a terminal 60 by a wire 14e. Should this last mentioned wire 14e break the inputs, V 1  V 2  to the comparator circuits 66, 68 increase and thus the effect is as if an alcohol concentration above the limit were flowing over the unit 50 and the air volume is below the limit. As described the control circuit 32 is connected to a locking mechanism in a vehicle, the locking mechanism being actuated, thus not allowing the vehicle to be driven if the alcohol concentration in the intended drivers' breath is above the allowable limit and/or the air volume provided by the intended driver is below the minimum limit and/or if a wire is broken. When the apparatus is installed in a vehicle a normally open switch 38 in the power supply means 24 is operative to close responsive to the locked condition of the door of the vehicle and the seated condition of the intended driver.