Patent Application
20090071226
The present invention relates to a test adapter for a gas-measuring device.
A measuring device for gas analysis, in which test gas is admitted to the gas sensor of a measuring head by means of a measured gas pump, is known from DE 102 31 515 C1, which corresponds to U.S. Pat. No. 6,701,773 which is incorporated by reference. A plug-in adapter, which has individual gas ducts, via which measured gas is drawn in by means of the measured gas pump and is delivered to the gas-specific surface of the gas sensor, is connected to the measuring head.
The prior-art gas-measuring device is also suitable for detecting volatile substances, which are adsorbed by the pump diaphragm of the measuring gas pump. The plug-in adapter is attached for this to the measuring head such that the gas sensor is located in front of the measured gas pump and is directly exposed to the volatile substance.
The prior-art gas-measuring device is suitable for continuous gas sampling, during which measured gas is drawn from a gas source.
A function test can be carried out with the prior-art gas-measuring device only by connecting it to a test gas source. Carrying along test gas sources makes handling difficult, especially because a simple function test, to be performed to determine whether or not a gas-measuring device responds to a certain gas, is sufficient in many cases.
Multi-gas-measuring devices, with which different components in a gas sample can be detected simultaneously, are known. Such multi-gas-measuring devices contain different measuring systems, in which infrared optical, electrochemical or catalytic detection methods are used. Multi-gas-measuring devices are often also designed as compact, portable measuring devices, which can simply be carried along and perform the gas concentration measurement directly at a possible hazard site.
The calibration of such gas-measuring devices for combustible materials with high-boiling hydrocarbons such as nonane and xylene is very complicated and cumbersome according to the current state of the art. Nonane is used as an additive in motor fuels, is readily combustible and has a gasoline-like odor. It is known to use, e.g., a calibration chamber for this, in which a certain quantity of liquid is dispensed into a known chamber volume by means of a plunger syringe and evaporated. The device to be calibrated is connected to the chamber. At the same time, a fan present in the chamber must be started in order to swirl the vapor. Handling requires utmost care because possible leaks in the chamber or errors in dispensing the liquid may lead to incorrect calibration. The high-boiling hydrocarbons evaporate very slowly at low ambient temperatures and lead to additional errors.
If the so-called saturated vapor calibration is used, relatively large quantities of liquid must be dispensed into the calibrating volume and ventilated there until a maximum vapor pressure becomes established, which depends on the temperature only. This temperature is measured with an additional temperature measuring device, and the concentration is determined from corresponding charts or diagrams.
An object of the present invention is to provide a device for saturated vapor calibration for gas-measuring devices.
According to the present invention, a test adapter is provided comprising a shell adapted to the geometric, external dimensions of the gas-measuring device with an integrated temperature measurement. The shell has a depression for receiving the sample liquid in the area of the gas-sensitive surface of the gas-measuring device. The upper side of the depression is located directly at the gas-sensitive surface of the gas-measuring device. The liquid level of the sample liquid within the depression is selected to be such that a gas volume in which the saturated vapor concentration of the sample liquid becomes established is present between the gas-sensitive surface and the sample liquid.
A stepped filling level indicator, whose lower step indicates the minimum filling level and whose upper step indicates the maximum filling level, is advantageously provided within the depression. The sample liquid can be filled into the depression by means of a syringe. The temperature indicator is advantageously designed in the form of a temperature measuring strip, which is arranged within the test adapter on the surface facing the gas-measuring device. Thus, the temperature-measuring strip is located in the immediate vicinity of the depression provided with the sample liquid.
The test adapter has an edge, which extends peripherally at least partially and into which the gas-measuring device is inserted. The peripheral edge is adapted to the outer contour of the housing of the gas-measuring device, so that the gas-sensitive surface of the gas-measuring device is located exactly above the depression of the test adapter and covers the depression from the top.
On its underside, the test adapter has feet, with which it can be placed on a horizontal surface, especially a table.
The adapter housing is shaped to receive the one side of the gas-measuring device having the gas sensitive surface. The depression of the adapter surface being arranged in an area of the gas sensitive surface when the gas-measuring device is received by the adapter housing. The depression and the adapter housing being arranged to hold saturated vapors of the sample liquid in communication with the gas sensitive surface of the gas-measuring device when the gas-measuring device is received by the adapter housing.
In particular, the depression and the adapter housing are shaped to entrap the saturated vapors of the sample liquid between the one side of the gas-measuring device and the side of the adapter housing with the depression, when the gas-measuring device is received by the adapter housing.
The function of the gas-measuring device is checked such that the test adapter is first placed on a horizontal surface and the depression is filled with sample liquid. The liquid level of the sample liquid is set within the depression such that it is between the minimum mark and maximum mark. The gas-measuring device is then placed onto the test adapter such that the gas-sensitive surface lies above the depression. The inner contour of the test adapter and the edge extending peripherally on the outside are designed such that the gas-measuring device can be connected to the test adapter in a preferred position only. The function test is carried out automatically by the gas-measuring device after the saturated vapor atmosphere of the sample liquid has acted on the gas-sensitive surface of the gas-measuring device for a certain time. After conclusion of the function test, the gas-measuring device sends a signal tone, which signals the end of the testing and calibration phase.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.
In the drawings:
Referring to the drawings in particular,
On its upper side, the test adapter 2 has a peripheral edge 7, which has a design corresponding to the outer contour of the housing 3. The test adapter 2 has feet 8 on its underside, with which the test adapter 2 can be placed on a horizontal surface 9. The test adapter has a depression 10 for receiving a sample liquid in the area of the gas-sensitive surface 5 of the gas-measuring device 1.
While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2007 044 179.9 | Sep 2007 | DE | national |
This application claims the benefit of priority under 35 U.S.C. §119 of German Patent Application 10 2007 044 179.9 filed 15 Sep. 2007, the entire contents of which are incorporated herein by reference.
