The Ideal 61-830 VPM Voltage Performance Monitor is a plug-in power quality monitor. It identifies sags, swells, impulses and harmonic distortion. The VPM also logs time, severity and duration of events and displays these records on the digital illuminated display. Main application is to determine if power quality problems are related to power supply or equipment in the facility, to verify if voltage meets equipment needs, and to monitor the quality and reliability of voltage supplied to equipment. The Ideal 61-830 can measure 85-265V AC, 45-65Hz and is Cat III - 300V and is powered by 3 AA batteries. The part number 61-830 includes the VPM monitor, various wall plug adapters and a durable carry case. Large display (which automatically rotates 180 degrees in case you need to plug it in upside down).