> you can divide down to say +/- 12V and use CMOS switch.
> Then higher precision for the final attenuator.
>=20
> What accuracy is needed?

That should be sorted by using a calibration table in EEPROM.


> 1kV needs 1M Ohm for 1mA, More than 4M7 precision resistors are
expensive.

But I would want to use multiple resistors in the top arm of the divider
anyway, to lower the voltage across each resistor. High voltage
resistors are also not cheap. So using, say 5, 1M close tolerance
resistors in the upper arm would give you around 200V across each,
doable with cheaper standard resistors, and a 1% resistor for the bottom
arm, value selected for the maximum value the switch can tolerate with
some safety margin, and then under test the actual ratio is stored as a
calibration value for each resistor string.
--=20
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--=20
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