A tank filled with water is covered by a layer of oil containing carbon black. A radiation source preferably a high intensity visible spectrum light is aimed at the bottom surface of the oil/carbon layer. A radiation detector is placed parallel with and immediately above the oil/carbon layer. In operation, the oil/carbon layer will offer an opaque surface thereby preventing the passage of radiation. A bubble rising in the water will momentarily penetrate the oil/carbon layer. If the bubble diameter is greater than the oil/carbon layer thickness, the radiation will pass through the oil/carbon layer. Once the bubble bursts, the oil/carbon layer will immediately heal, thereby sealing off the passage of radiation. The radiation detector will detect any radiation passing through the oil/carbon layer. A passing bubble will be indicated as a discrete blast of radiation. The radiation detector preferably consists of an array of radiation detectors. The array produces indicia of X-Y location as a consequence of correlation of position within the array with radiation detection.

A detector and counter for drainage devices is provided which will detect the passage of air through an underwater seal chamber. A signal is transmitted as a result of the detection of the presence of air or a bubble within an underwater seal chamber and an output circuit responsive to these signals measures the time interval between bubbles. In addition, a counter counts the total number of bubbles passing through the underwater seal over a selected period of time. The bubble detector when used with a pleural drainage device provides a diagnostic tool for a physican in determining the condition of a patient with a pleural air leak by indicating the elapsed time between bubbles and the total volume of air leak over the selected period of time.

An apparatus and method for testing for gas leaks in waterproof gloves and glove inserts by applying gas under controlled pressure into a confined glove or insert and measuring bubbling or lack thereof in a suitable reservoir of liquid. The glove is not wet by liquid.

The invention provides an improved bubble leak tester, and associated method for performing a leak test and operating the leak tester, to test for leaks in a test part. The apparatus and methods of the invention allow for simple, inexpensive, quick and accurate testing of the test part, provides a visual indication of a leak, and eliminates the part damage and clean-up associated with conventional water immersion tests. Further, the apparatus and methods in accordance with the invention control liquid backflow, so that contamination and damage to the device is reduced. In one embodiment in accordance with the invention, a leak tester is provided that is connectable to a reference volume and a test volume for determining the presence of a leak in the test volume. The leak tester comprises a reference port for connection to the reference volume, a test port for connection to the test volume, a bubble chamber connected between the reference port and the test port, and apparatus for selectively controlling flow between the reference port and the bubble chamber and between the test port and the bubble chamber.

A communication device (100) is provided with a technique (400) for self-diagnosing an air leak. The leak is determined without having to open the communication device by applying a temporary excitation signal to the speaker terminals (402) to produce a damped response (404) and then monitoring the damped response (406) of the speaker.