DISPOSITIF D'ACTIVATION D'UN APPAREIL DE MESURE D'EMISSION ACOUSTIQUE PAR DETECTION DU BRUIT DE FOND

LA PRESENTE INVENTION PERMET DE N'ACTIVER UN APPAREIL DE MESURE D'EMISSION ACOUSTIQUE QU'A DES PERIODES CRITIQUES, REPEREES PAR LA DETECTION DU BRUIT DE FOND A PARTIR D'UN NIVEAU DE REFERENCE.UN CAPTEUR 1 D'EMISSION ACOUSTIQUE ENVOIE UN SIGNAL EN PERMANENCE A UN CIRCUIT DE DETECTION 2 QUI FOURNIT L'ENVELOPPE DE MODULATION SUPERIEURE DU BRUIT DE FOND A UN COMPARATEUR 3 A UN NIVEAU DE REFERENCE FOURNI PAR UN ORGANE DE CONTROLE 4. QUAND LE NIVEAU MOYEN DU BRUIT DE FOND DEPASSE CELUI DE LA REFERENCE, LE COMPARATEUR 3 DELIVRE UN SIGNAL D'ACTIVATION DE L'ENSEMBLE D'ENTREE-SORTIE 5 DE L'APPAREIL DE MESURE.APPLICATION AU CONTROLE ACOUSTIQUE D'INSTALLATIONS INDUSTRIELLES EN GENIE ATOMIQUE OU GENIE CHIMIQUE. 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.