Extech 407026-NIST - NIST Calibration Certificate - Light Meter Heavy Duty with PC Interface features: Enhance accuracy by selecting one of four lighting types plus PC interface; % displays differential from reference point; "ZERO" Re-Calibration; Enhance accuracy by selecting lighting type Tungsten/Daylight, Fluorescent, Sodium, Mercury); Data Hold, Min/Max/Avg readings; Built-in RS-232 PC serial interface.