Measuring and testing – Instrument proving or calibrating – Volume of flow – speed of flow – volume rate of flow – or mass...
Patent
1990-12-21
1994-03-15
Williams, Hezron E.
Measuring and testing
Instrument proving or calibrating
Volume of flow, speed of flow, volume rate of flow, or mass...
73 1G, 204401, 436 8, G01N 2726
Patent
active
052937704
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a calibration device for use in calibrating a sensor, and of the type comprising a calibration housing with a calibration chamber, said calibration chamber containing a fluid for use in the calibration process and further including a wall part adapted to cooperate with the sensor in such a way that during the calibration process the requisite contact for this purpose is established between the sensor and the fluid contained in the calibration chamber.
Sensors are utilized in a wide range of applications in which more or less frequently a measurement of the content of one or more components in a given fluid is desired, or where it is desired to establish a measurement of the condition of such a fluid e.g. as expressed by the pH-value of the fluid.
The components in question may exist in a gaseous state or in a non-gaseous state and may be present in either a liquid or in a gas.
The following components may be stated as examples of non-gaseous components the content of which it is often desired to register: Ions (such as H.sup.+, K.sup.+, Na.sup.+, Ca.sup.2+, Cu.sup.2+, Cl.sup.- etc.) and organic molecules (e.g. glucose, metabolites, hormones, enzymes etc.). Examples of gaseous components include various gases such as O.sub.2, NH.sub.3 and CO.sub.2. Such gases are typically registered in the form of their respective partial gas pressures (pO.sub.2, pNH.sub.3 and pCO.sub.2). Examples of fluids in which the above components may be present are various physiological liquids (e.g blood), various types of water (e.g. fresh water, seawater, sewage water etc.) nutritive mediums, laboratory samples of all sorts, flue gases, air etc.
As to typical sensors these include sensors based on various electro-chemical measuring principles such as potentiometry, amperometry and polarography as well as optical sensors, i.e. sensors utilizing an optical response phenomenon.
Common to the majority of these sensors is the fact that prior to a measuring sequence the sensor with accompanying equipment must be calibrated.
Such a calibration typically involves contacting the sensor with a fluid having a known content of the component to which the sensor is sensitive.
Thus, in performing the calibration process it is necessary to have access to a calibration fluid of a known composition. Also it is advantageous if the calibration fluid is available in a form in which the requisite contact with the sensor is readily obtained.
Even though it is sometimes necessary or preferred to prepare the actual calibration fluid immediately before the calibration process, it is normally preferred to make use of a prefabricated calibration fluid. In case of such a prefabricated calibration fluid it goes without saying that it is of vital importance to store said fluid under such conditions that the original composition does not change with time e.g. as a result of mixing or reaction with other materials or the surroundings.
In this connection it is noted that handling of calibration fluids intended for use in calibrating gas sensors, in particular sensors for pO.sub.2 and pCO.sub.2, poses special problems due to the fact that the contained components tend to interact with the surroundings. Consequently it is necessary, both during storage and use of such fluids, to take special precautions in order to minimize or eliminate the risk of any such unwanted interaction. The optimum solution to this problem is of course to store the fluid in question in a sealed chamber until the time of use. In connection with the calibration process proper the best solution is to ensure that the contact between the sensor and the calibration fluid be established in a way which positively excludes any prior contact between the calibration fluid and the surroundings.
Another demand which has become topical concurrent with the development of portable measuring equipment is, that the auxiliary equipment used in connection with the portable measuring equipment proper, must not in itself--due to its size, shape or weight--reduce the portability of the
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Leaflet relating to the TCM3-Monitor.
Copies of pp. 1.1-1.5 from a User's Handbook describing the TCM3.
Hansen Steffen T.
Sorensen Poul R.
Dombroske George M.
Klein David M.
Radiometer A/S
Williams Hezron E.
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