| 摘要 |
PCT No. PCT/EP96/00065 Sec. 371 Date Jul. 11, 1997 Sec. 102(e) Date Jul. 11, 1997 PCT Filed Jan. 9, 1996 PCT Pub. No. WO96/21850 PCT Pub. Date Jul. 18, 1996The invention concerns a method and device for checking tightness of containers, housings and similar test objects (15). The test object (15) is subjected to a pressurized test gas. If a leak (28) is present, test gas escapes from the text object (15) and is exposed in a test chamber (18) to an intensity-modulated electromagnetic wave field emitted by a laser (1). The wave field contains frequency components which are absorbed by the test gas to produce a photo-acoustic signal indicative of the presence of a leak. To facilitate a quantitative tightness examination even using a longitudinal multimode laser with several laser modes which can be absorbed by the test gas, it is proposed according to the present invention that the temperature of the laser (1) should be set to a reference value and the excitation power of the laser should be kept at a constant mean level, so that the photo-acoustic signal can be measured and evaluated as a measure of the test gas concentration in the test chamber and/or of the size of the leak from the test object. To improve measuring accuracy, a reference chamber (5) with a predetermined test gas concentration is in addition exposed to the intensity-modulated wave field emitted by the laser (1); the photo-acoustic signal (6) produced in the reference chamber (5) is then used either for standardization purposes for when the test gas concentration in the test chamber (18) is determined, or for adjusting the reference temperature value (Tref) of the laser (1) to a predetermined working point.
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