DEVICE FOR ACOUSTIC-EMISSION CONTROL OVER COMPOSITE MATERIALS Russian patent published in 2013 - IPC G01N29/14 

FIELD: physics.

SUBSTANCE: proposed device comprises two electro-acoustic channels including receiving transducer, preamplifier with 40 dB gain, filter, and primary amplifier. Note here that first electro-acoustic channel comprises receiving transducer with resonance frequency of 100…200 kHz, band filter with bandwidth of 20…200 kHz suppression outside the band of 40 dB, primary amplifier with controlled gain of 20…60 dB, envelope detector and ADC. Second electro-acoustic transducer comprises receiving transducer with resonance frequency of 20…50 kHz, low-pass filter with cut-off frequency of 20 kHz and high frequency suppression of 40 dB, primary amplifier with gain of 20 dB, envelope detector and ADC. Note here that first channel envelope detector output and second channel primary amplifier output are connected to ADC of discrete sound adapter with sampling rate of 192 kHz normalised by signal/noise ratio and normalised irregularity of gain frequency characteristic. While DAC integrated in PC sound adapter mother board is used to generate variable-amplitude meander used in first channel amplifier gain control. Note here that ADC signals are received as signals bearing data on acoustic event when and only when difference in levels of first and second channel signals exceeds definite preset threshold magnitude. Note also signal discrimination and selection of gain magnitudes are performed by control program.

EFFECT: higher noise immunity, expanded control range.

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