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Vacuum leak detector

  • US 4,635,042 A
  • Filed: 03/21/1984
  • Issued: 01/06/1987
  • Est. Priority Date: 03/21/1984
  • Status: Expired due to Fees
First Claim
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1. A device for locating sources of ultrasonic sound waves within a relatively narrow frequency band indigenous to vacuum leaks, comprising:

  • a hand held probe;

    a frequency sensitive ultrasonic transducer supported within the probe for providing an electrical output in response to incident ultrasound waves, and having a greater sensitivity to ultrasound waves within said narrow band than to at least certain other frequencies, the transducer exhibiting a sensitivity peak within the narrow band at about 40 kilohertz and at least one other sensitivity peak outside the narrow band;

    frequency selective means coupled to the transducer and located within the probe for amplifying the transducer electrical output, said amplifying means exhibiting a greater gain to electrical signals having frequencies within the narrow band than to at least certain other frequencies, the amplifying means comprising a series of concatenated amplifier stages, each having a low frequency blocking alternating current input circuit and a high frequency passing negative feedback circuit for reducing amplifier gain at higher frequencies, the two circuits jointly effective to endow the amplifying means with relatively narrow band pass characteristics, a half-wave rectifier circuit connected to the output of the last of the concatenated stages and a direct current amplifier for providing an output voltage level proportional to the magnitude of the halfwave rectifier output;

    an electrically conductive shield within the probe surrounding the amplifying means; and

    an indicator containing packet comprising display means coupled to the amplifying means and located remotely from the probe for providing a visible qualitative indication of the intensity of the ultrasound waves within the narrow band incident the transducer, the display means comprising a multisegment bar graph connected to the direct current amplifier;

    the indicator containing packet adapted to also contain a battery, operator actuable sensitivity control means for selectively varying the gain of the direct current amplifier, and an audible alarm device a threshold circuit coupling the audible alarm device to the direct current amplifier and to the display means for sounding the alarm device when the output voltage level exceeds a preselected level as indicated by one of the segments of the bar graph.

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