WO1990004174A1

WO1990004174A1 - Device for calibration of gas sensors

Info

Publication number: WO1990004174A1
Application number: PCT/GB1989/001182
Authority: WO
Inventors: Dawood Parker
Original assignee: Franklin Instruments Inc.
Priority date: 1988-10-05
Filing date: 1989-10-05
Publication date: 1990-04-19
Also published as: GB8823321D0

Abstract

The device comprises a package, typically in the form of a vacuum-formed sheet (1) with an array of depressions (2) which are hermetically sealed by a layer of metal foil (5) so as to form a corresponding number of individually hermetically sealed compartments. In each compartment is a tablet (4a) of silicone rubber containing dissolved gas (such as carbon dioxide) in a predetermined proportion.

Description

Device for Calibration of Gas Sensors

The present invention is concerned with devices for calibration of gas sensors.

According to the present invention, there is provided a device for calibration of a gas sensor, which comprises a package containing a plurality of solid bodies each having a predetermined proportion of gas dissolved therein, and each being individually hermetically sealed in a separate compartment in said package.

Each of the solid bodies has preferably been allowed to equilibrate with a gas present in a predetermined proportion in an atmosphere; for example, an atmosphere containing 5% or 10% carbon dioxide. The solid bodies are preferably such that they are substantially permeable to the gas to be dissolved therein; the bodies should, however be preferably free of pores of a size such that they would be visible to the naked eye. A typical material for the bodies (particularly when the gas to be dissolved therein is carbon dioxide) is a silicone rubber, such as the elastomeric material commercially available under the trade mark "Silastic". The present invention further comprises a method of calibration of a gas sensor, which comprises providing a device according to the invention, breaking a seal of an individual compartment of the package so as to expose the body retained in the- compartment with a broken seal, placing the body in close proximity to a gas sensor capable of producing an output indicative of the proportion of the relevant gas in an atmosphere, and calibrating the output of the gas sensor to give an output corresponding to the predetermined proportion of the relevant gas in the body.

The body may be placed in close proximity -to the gas sensor while it is still in the compartment with the broken seal, the compartment being placed around the gas sensor, generally so as to form an enclosure for the gas sensor.

A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a schematic plan view, partly cut away, of a package according to the invention; and

Figure 2 is side elevation of the package of Figure 1.

Referring to the drawings, there is shown a package comprising a vacuum-formed plastics sheet 1 having two rows of generally circular vacuum-formed depressions 2. Located at the base 3 of each depression is a solid tablet 4a, 4b, 4c, 4d etc. of silicone rubber or the like. A layer 5 of aluminium foil or the like is secured to the sheet in such a way as to hermetically seal each individual depression; each tablet is present in an individual gas space and hermetically sealed and isolated from other similar tablets.

In the illustrated embodiment, a part 6 of the foil layer has been torn away to provide access to an individual tablet 4a and to permit the latter to be removed from the package. Each tablet has been previously equilibrated with an atmosphere containing a predetermined proportion of a predetermined gas (such as an atmosphere of 5% or 107o carbon dioxide) such that the gas is dissolved in the material consticuting the tablet. Each tablet, on removal from the relevant part of the package, can be used to calibrate an appropriate gas sensor (such as a carbon dioxide sensor) .

In one preferred embodiment of the invention, different tablets may have been equilibrated with atmospheres containing different concentrations of the relevant gas, and provided with indicia representing the concentration in the gas with which it has been equilibrated.

Various modifications of the illustrated embodiment are possible; for example, the tablets may be individually hermetically sealed between aluminium foil sheets, in a manner similar to that used for certain medicinal tablets. When a vacuum-formed plastics sheet is used, it may be transparent (for example, in the nature of a blister pack or the like), or opaque.

Claims

CLAIMS :

1. A device for calibration of a gas sensor, which comprises a package containing a plurality of solid bodies each having a predetermined proportion of gas dissolved therein, and each being individually hermetically sealed in a separate compartment in said package.

2. A device according to claim 1, wherein said solid bodies are permeable to said gas but substantially free of pores of a size visible to the naked eye.

3. A device according to claim 1 or 2, wherein said solid bodies are of silicone rubber.

4. A device according to any of claims 1 to 3, wherein said gas is carbon dioxide.

5. A device according to any of claims 1 to 4, wherein said package comprises a formed plastics sheet having an array of depressions therein each receiving one said body, and a foil layer secured to said sheet so as to hermetically seal each individual depression.

6. A device according to claim 5, wherein one said body is present in each said depression.

7. A device according to any of claims 1 to 6, wherein a first group of said bodies have been equilibrated with an atmosphere containing a first predetermined proportion of said gas and a second group of said bodies have been equilibrated with a second predetermined proportion of said gas.

8. A device according to claim 7, which further comprises indicia representing the concentration of said gas for each of said groups of bodies.

9. A method Of calibration of a gas sensor, which comprises providing a device according to any of claims 1 to 8, breaking a seal of an individual compartment of said package SJD as to expose the body retained in said compartment, placing said body in close proximity to a gas sensor capable of producing an output indicative of the proportion of said gas in an atmosphere, and calibrating said output to give an output corresponding to the predetermined proportion of said gas in said body.

10. A method according to claim 9, wherein said body is placed in close proximity to the gas sensor while still in said compartment, the compartment being placed around said gas sensor.