How to create isolation for circuit where device connected to two high voltage supplies? One high voltage supply is working and another one will be activated if the first voltage supply stopped to work.

Hello,

I am working with high voltage supplies for Geiger-Muller counter. Since both supplies should be connected to the radiation detector, there should be included isolation (some kind of switch between two high voltage circuits). Supplies provide staircase outputs between 350 V and 500 V with 50 V step and 5 msec. delay.

How to isolate these two voltage supplies connected to anode of Geiger-Muller counter?

Thank you in advance,

Sveta