Method and apparatus for determining O2 and N2O in gas mixtures

Details Method and apparatus for determining O2 and N2O in gas mixtures Method and apparatus for determining O2 and N2O in gas mixtures

1999-10-13

2001-10-16

Warden, Sr., Robert J. (Department: 1744)

Electrolysis: processes, compositions used therein, and methods

Electrolytic analysis or testing

For nitrogen or nitrogen containing compound

C205S783000, C204S406000, C204S415000, C204S432000, C204S431000

Reexamination Certificate

active

06303018

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a method and device for the determination of oxygen (O
2
) and nitrous oxide (N
2
O) concentrations in gas mixtures by quantitative electrochemical reaction.
RELATED ART
U.S. Pat. No. Re 31,914 discloses an electrochemical method for the determination of toxic gases in air. Further, U.S. Pat. Nos. 4,495,051, 4,894,138 and 4,914,424 describe galvanic cells which are used as oxygen sensors. In particular, WO 97/35186 discloses a method and a device for determining the proportion of oxygen in the breathing air delivered in medical ventilation devices. In this case, an alkaline zinc-air cell is used as a sensor.
Alkaline zinc-air cells are made as button cells on a mass-production scale worldwide and are used as primary cells, in particular, in hearing aids. If the supply of oxygen is restricted by flow and/or diffusion obstacles, then the maximum deliverable current becomes the limiting current and then depends only on the oxygen concentration in the medium next to the O
2
cathode. The zinc-air cell thereby becomes a sensor cell for oxygen concentration measurement or oxygen quantity measurement when used in closed volume.
When monitoring patients' breathing air in nitrous oxide anesthesia, it has been found that it is not sufficient merely to measure the oxygen content, but it is also necessary to control the nitrous oxide concentration.
OBJECTS
An object of the invention is accordingly to provide a method and device for the determination of oxygen (O
2
) and nitrous oxide (N
2
O) concentrations in gas mixtures, with which oxygen and nitrous oxide in breathing air can be determined in tandem.
SUMMARY OF THE INVENTION
The electrochemical working ranges are set by setting voltage ranges. This being the case, a lower voltage range of about 0.4 to 0.8 V and an upper voltage range of about 0.8 and 1.5 V are set. The virtually simultaneous determination of nitrous oxide and oxygen is preferably achieved by temporarily bypassing a diode to set the lower voltage range.
The device according to the invention for carrying out the method includes a casing which accommodates the gas mixtures, a zinc-air cell, and a circuit which is connected to the electrodes of the zinc-air cell and contains diodes and resistors as well as tap points and arrangements for measuring and indicating the current value. The circuit preferably contains a periodically actuable bypass switch which is connected in parallel with at least one of the diodes. In one embodiment of the circuit, the diodes are Zener diodes.


REFERENCES:
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patent: 4956063 (1990-09-01), Hale
patent: 5902467 (1999-05-01), Wang et al.
patent: 35186 (1997-09-01), None

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