I have the circuit that you see below.
My load is a photomultiplier tube equivalent to a 3.63Mohm resistor.
My power supply can deliver max 4W (2kV and 2mA). I use it on 1100V and the load draws ~350uA. I want to monitor the current with the shunt resistor technique. Only high side current sense would work, because the load is tied to the circuit ground. I possess 0.1% tolerance resistors up to 500 ohm and 1% tolerance up to 1Mohm. I can spare up to 10 volts to drop across the shunt resistor.
I can't find a circuit with current amplifier able to withstand the 1100 volts relative to the ground on its inputs.
I've seen the Maxim application note with the optocoupler, but it won't work on my simulation package (multisim). I'm currently awaiting the ICs to test it for real.