Extech 407730-NIST - NIST Calibration Certificate - Digital Sound Level Meter features:?áAnalog bargraph with 50dB range updates every 40ms; ??2dB accuracy with 0.1dB resolution;?áA+C weighting;?áAC analog output; Record Max/Min values over time;?áUtilizes 0.5"(12.7mm) electret condenser microphone;?á40 to 130dB measuring range.