Thermal measuring and testing – Temperature measurement – In spaced noncontact relationship to specimen
Patent
1998-10-30
2000-11-28
Bennett, G. Bradley
Thermal measuring and testing
Temperature measurement
In spaced noncontact relationship to specimen
374132, 374133, 128664, G01J 504, G01J 506, A61B 600
Patent
active
061525952
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a probe tip for a radiation thermometer according to the prior-art portion of claim 1 as well as to a radiation thermometer incorporating such a probe tip. The present application further relates to a method for reducing temperature gradients in the radiation sensor of a probe tip of the prior art.
Radiation thermometers are increasingly used for quick and accurate determination of a person's body temperature. This involves the simple procedure of introducing the thermometer's probe tip into the ear canal in order to measure the infrared emissions from the tympanic membrane which are an accurate indication of the body's temperature and more responsive to changes in temperature than is the case with oral, rectal or axillary measurements. By comparison with conventional clinical thermometers filled with mercury, radiation thermometers have proven to be not only significantly more rapid and accurate, but they also eliminate the risk of communicating infections resulting from contact with mucous membranes as may happen, for example, when oral or rectal measurements are taken with mercury-filled thermometers. In addition, the risk of perforating the rectum is eliminated, a permanent hazard when taking babies and children's temperature with conventional thermometers.
The probe tips of radiation thermometers typically comprise an opening for admitting the infrared radiation to be measured which is directed through an infrared waveguide extending from the opening to a thermal radiation sensor as, for example, a pyroelectric sensor, a thermopile or a bolometer device. This device converts the partial temperature increase produced in the sensor into an electrical output voltage from which the target temperature is determined by means of a downstream electronic measurement circuitry.
When temperature gradients occur in such a probe tip as they may develop, for example, when the probe tip is heated due to contact with the ear canal, measurement errors are frequently introduced because of the sensitivity of thermal radiation sensors unless appropriate countermeasures are taken.
To avoid such erroneous readings, a variety of different methods are known in the art.
Thus, for example, it is proposed in U.S. Pat. No. 4,602,642 to preheat the probe tip of a clinical radiation thermometer to the expected target temperature of about 37.degree. C. prior to taking the measurement in order to thereby minimize temperature gradients between the measuring point which is conventionally the auditory meatus, and the probe tip with the radiation sensor received therein, thereby minimizing the effect of such temperature gradients on the measurement accuracy. However, preheating the probe tip uniformly involves rather an elaborate technique which has a detrimental effect not only on the manufacturing process and the associated cost, but also on the user friendliness of such a probe tip. Moreover, the necessary preheating period is rather long, preventing measurements to be taken readily and making utilization appear impractical because of the attendant high power consumption, in particular where battery-powered radiation thermometers are used.
Another possibility involves integrating the radiation sensor into a large thermal mass so that a heat input results in only a low temperature rise and low temperature gradients. Thus, for example, EP 0 441 866 B1 describes a probe tip in which the sensor sits on a heat sink and the heat from the ear is directed around the sensor into the heat sink, being thus kept away from the sensor. In U.S. Pat. No. 4,895,164 a substantial part of the waveguide together with the sensor device is surrounded by a metal block of sufficient size and good heat conductive properties in order to ensure substantially isothermal conditions. The disadvantage of this approach is, however, that large thermal masses make a thermometer difficult to handle and heavy, so that small pivotal probe tips are not possible. In addition, design and construction constraints are high.
According to the teaching
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Beerwerth Frank
Honnefeller Katja
Kraus Bernhard
Bennett G. Bradley
Braun GmbH
Verbitsky G.
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