The UT503PV is built for solar work: it measures insulation resistance on live photovoltaic systems at up to DC 1000 V, so a string can be tested without taking the array offline or short-circuiting panels — including after dark. It tests to IEC 62446 with test voltages from 125 V to 1000 V and a measurement range up to 4000 MΩ, and it's rated CAT II 1000 V / CAT III 600 V with an IP54 sealed body for outdoor use.

Stepped-voltage testing, a comparison function, automatic discharge, and a high-voltage alarm cover the safety and diagnostic basics, while 1000 result sets store on-board and transfer over USB or a Bluetooth app for commissioning reports. It's backed by UNI-T's nearly 40 years of test-meter manufacturing.