How to measure voltage of above 10kV using an MCU

[samuelr]

I am trying to find a way to safely sample a high voltage output which will travel from about 1kV to 20kV (ramp).

I think using a resistor divider should do the job. I have been successful at 1 kV - 2 kV range. I am just wondering if just by using a high impedance resistor will do the trick.
Any advise?

 

[Vbase]

Use carbon composite resistors in series. If you find the datasheet you will be able to tell what is the max working voltage, if it's say 500V series at least 20 of them and put them inside plastic rube.
Don't use metal film resistors or carbon film resistors, they often arc between the windings and go open circuit. They also have higher inductance that increases the error with the input capacitance of the ADC.

 

[betwixt]

I agree with Vbase over the chain of resistors but I would also include a high input impedance buffer amplifier between the voltage tap and the MCU. The reason is that most MCU, assuming you are feeding directly into an ADC, need to see a low impedance. The chain of inevitably high value resistors is likely to cause serious reading errors because of the long time constant they create with the ADC input circuits. A buffer will increase the current available to the ADC while not unduly loading the voltage from your divider chain.

Brian.