I use microcontroller to measure high voltage DC so I need to isolate GND1 of high voltage to GND2 of the microcontroller. Can anybody suggest the way to do. Thank in advance.
Make sure that the two (low voltage and high voltage) sections do not share their GROUND paths. TO achieve this, route the two sections seperately and bring the GROUNDS to a common point.
Also ensure that the trace catering to high voltage/ power has enough isolation (distance) and strengh (trace width).
Depending on how high your DC voltage is you could either isolate analog with e.g. an ISO 122 or ISO 124 or go digital with the A/D converter on the high voltage side. In this case you could use optocouplers or better ADUM120X from Analog Devices (very fast and easy to handle). You will probably need a DC/DC converter to power electronics on the high voltage side.