Its small size, makes Sound Level Pen convenient for testing many sound meter applications. Auto-ranging with simple one-button operation. Press once to begin reading sound levels. Press the button a second time and the display holds the maximum reading, updating as new maximums are reached. Hold the button for 2 seconds to turn the unit off. Measures the 30 to 130 dB range in the "A" scale, with an accuracy of ±1.5 dB. The display provides 0.1 dB resolution, under range, over range and low battery indicators. The Sound Level Pen calibrates electronically to its own internal oscillator or external 2-Pt. Acoustical Calibrator 850016. Comes ready to use with two AAA batteries, instructions, calibration screwdriver, and a windscreen. N.I.S.T. Traceable Certification Report available, or calibrate anytime using optional Acoustical Calibrator 850016.