1. Field of the Invention
The present invention relates to a method for calibrating an infrared thermometer, particularly to a method for calibrating an infrared thermometer at different ambient temperatures.
2. Description of the Related Art
U.S. Pat. No. 6,065,866 discloses a method for calibrating an infrared thermometer. In this prior art, an infrared thermometer detects two black bodies 1 and 2, which respectively have given temperatures Ts(1) and Ts(2), at an identical ambient temperature T
and the value of the sensitivity S of the radiation sensor is
Then, the values of the ambient temperature T
Infrared thermometers are very sensitive to ambient temperature. For example, when the measurement accuracy of an infrared ear thermometer is ±0.2° C., the variation of ambient temperature ΔT
Accordingly, the present invention proposes a new method for calibrating an infrared thermometer to overcome the above-mentioned problems.
One objective of the present invention is to provide a method for calibrating an infrared thermometer, wherein two test objects are respectively placed in environments having different ambient temperatures and detected by an infrared thermometer, and different output signals of the radiation sensor of the infrared thermometer and different resistances of the ambient-temperature sensor of the infrared thermometer are obtained from the two test objects, and the sensitivity of the radiation sensor and the reference resistance of the ambient-temperature sensor are worked out from the output signals and resistances.
Another objective of the present invention is to provide a method for calibrating an infrared thermometer, which is free of the limitation of an identical ambient temperature and can work at different ambient temperatures without investing much money in temperature-control equipment.
The method for calibrating an infrared thermometer proposed by the present invention is to generate a sensitivity value S of the radiation sensor of an infrared thermometer and a reference resistance value RO of the ambient-temperature sensor of the infrared thermometer. In the method of the present invention, an infrared thermometer first detects a first test object having a given temperature T
and a, b and c are temperature coefficients. Thereby, the reference resistance value RO of the ambient-temperature sensor can be worked out. Next, the reference resistance value RO is used to calculate the ambient temperatures T
Below, the embodiments are described in detail in cooperation with the attached drawings to make easily understood the objectives, technical contents, characteristics and accomplishments of the present invention.
The FIGURE is a flowchart of a method for calibrating an infrared thermometer according to the present invention.
An infrared thermometer has a radiation sensor and an ambient-temperature sensor, and a method for calibrating an infrared thermometer according to the present invention is to obtain the sensitivity S of the radiation sensor and the reference resistance RO of the ambient-temperature sensor, wherein the reference resistance RO is the resistance at an ambient temperature of 25° C., i.e. to obtain these two calibrated parameters, S and RO.
Refer to the FIGURE, a flowchart of a method for calibrating an infrared thermometer according to the present invention. In preparation for the method of the present invention, a first test object having a given temperature T
In Step S3, the given values or the values obtained in Step S1 and Step S2 are substituted into Equation (2):
wherein T
From Equation (3) is worked out the sensitivity S of the radiation sensor:
The first ambient temperature T
wherein a, b and c are temperature coefficients of sensors, which are provided by the manufacturer. Then, Equation (5) is substituted into Equation (4) to obtain Equation (6):
According to from Step S3 to Step S5 shown in
In conclusion, the present invention proposed a method for calibrating an infrared thermometer, which can perform calibration in the environments having different ambient temperatures to obtain the sensitivity S of the radiation sensor and the reference resistance RO of the ambient-temperature sensor—the parameters needing calibration. Thus is overcome the conventional problem that an infrared thermometer must be calibrated at an identical ambient temperature, and also is saved the investment in the expensive temperature-control equipment.
The embodiments described above are only to demonstrate the characteristics and technical thoughts of the present invention to enable the persons skilled in the art to understand, make, and use the present invention. However, it is not intended to limit the scope of the present invention. Any equivalent modification or variation according to the spirit of the present invention is to be also included within the scope of the present invention.
Number | Date | Country | Kind |
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96104781 A | Feb 2007 | TW | national |
Number | Name | Date | Kind |
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5464284 | Rall | Nov 1995 | A |
6065866 | Kraus et al. | May 2000 | A |
7297938 | Fauci et al. | Nov 2007 | B2 |
Number | Date | Country | |
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20080192798 A1 | Aug 2008 | US |