In this paper will be presented a sound level meter calibration system using a commercial 24bits AD/DA converter. A software developed on LabVIEW language from National Instruments has been used to create IEC 60651 signals. The software generates pure tones arrays for verification of A, C and Flat frequency weightings, beside signals for verification of RMS detector by crest factor method, linearity level, fast and slow time weightings. These signals were built on 44.1kHz sampling rate with an effective dynamic range greater than 100dB, which is good enough for linearity level calibration. Customised software drivers developed on C language have been used to enable communication between LabVIEW and that commercial AD/DA system, allowing the standard signals generated in LabVIEW environment to reach the system's analogue outputs. All measurements were performed on class 0 and class 1 sound level meters. The system was calibrated by means other LabVIEW software that controls a Hewlett Packard 3458A multimeter which is the laboratory standard for AC voltage and total harmonic distortion (THD) measurements, and a HP53132A universal counter for frequency measurements. Finally will be presented advantages of using such calibration system.
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