high voltage voltmeter

There are times when it is necessary to measure high voltage.
For example, 10kV, 20kV and so on. You can certainly buy a high voltage voltmeter, but as far as I understand such devices are very expensive.
And you can make a pointer microampermeter.
The diagram of the voltmeter in the figure.
It is necessary to have 100 μA, as a rule their internal resistance is less than 1000 Ohm. A large internal resistance will be a shunt and will incorrectly show stress.
High-voltage resistance is also needed. I will not say exactly how they are called from you. Our name is KEV. The power of the resistance must be at least 1W.
The principle of calculating the voltmeter is based on Ohm's law and voltage dividers.
Resistors that are connected to the circuit in series with a device for measuring the voltage exceeding the maximum value for the given device voltage in n = U / Up times. (Up-allowable voltage for the device is looked at the passport)
Rd = (n-1) Rв, Rd-additional, Rp- device.
Foto KEV