Device for the activation of an apparatus for measuring acoustic emission by detection of background noise

• US 4,423,634 A
• Filed: 07/06/1981
• Issued: 01/03/1984
• Est. Priority Date: 07/08/1980
• Status: Expired due to Fees

• Current Assignee: CGR
• Original Assignee: CGR
• Inventors: Audenard, Bernard, Marini, Jean
• Primary Examiner(s): Ciarlante, Anthony V.
• Assistant Examiner(s): Carlson, David V.
• Application Number:
  US06/280,355
• Time in Patent Office: 911 Days
• Field of Search: 73/587, 73/801, 73/613, 73/593
• US Class Current: 73/587
• CPC Class Codes: G01H 3/12 by electric means G01H3/14 takes precedence

Abstract

An apparatus for measuring acoustic emission is activated only at critical periods which are determined by detection of the background noise from a reference level. An acoustic emission transducer continuously transmits a signal to a detection circuit which delivers the top modulation envelope of the background noise to a comparator at a reference level delivered by a control unit.

When a mean level of the background noise does not exceed a threshold reference level the AE is sampled at a low rate, f. When the background noise exceeds the threshold reference level the data sampling unit is activated to sample AE at a much higher rate F. Therefore AE is sampled at a high rate only when the pump or other machine under test is running and at a low rate when the article under test is not operating. The AE testing device also includes a frequency spectrum correlator which allows background noise to activate the increased sampling rate only if the noise is in a given frequency range.

Claims

1. A device for measuring acoustic emission, wherein said device comprises a detection circuit for detecting the background noise collected by transducers of the measuring apparatus;

means for comparing the signal generated by said detection circuit with a reference voltage and producing an output signal when the comparison indicates that the background noise level has increased above a certain threshold level; and

means for acquiring data at a first frequency, f, when no output signal is produced and when said output signal is produced acquiring data at a second frequency, F, greater than said first frequency, f.

2. A device according to claim 1 further including, a control unit for supplying said reference voltage to said comparing means.

3. A device according to claim 1, wherein each transducer further comprises a rectifier device.

4. A device according to claim 1, wherein the background noise detection circuit comprises a mean level integrator.

5. A device according to claim 4, wherein the background noise detection circuit comprises a correlator for receiving a signal which performs spectral discrimination.