The Extech 380803-NIST is a True RMS power analyzer and data logger. Appliance Tester/Power Analyzer simultaneously displays the Wattage, Power Factor or VA, Voltage or frequency (Hz), and Current (Amps) of the device or appliance tested. The built-in data logger can store up to 1,012 readings or you can save data directly to your PC using the built-in RS-232 port and included software. Additional features include: Max Hold, Data Hold, and overload protection. Battery or AC Adaptor Operation provides line isolation. With NIST Calibration.