Where can I find used/suplus/economical high voltage power supply
(0-20kV or more)which has output for voltage monitoring?

Don?t know your country so I can?t recommend specifically but there
are many sellers of second hand electronic test equipment. Included in
the range are oscilloscopes, signal generators etc and the occasional
HV power supplies. A little pricey. ?Hunting HiVolt? is one of the
best known in UK.

On the cheap, you can use the 25KV from a colour TV and monitor the
voltage with a HV test probe (readily available) specifically made for
this purpose, coupled to a DVM.

But if you want genuine kit to do the job, search for ?test
equipment?, including other terms such as PSU, HV etc, or simply
?Hunting HiVolt?.

Best

Guzzi,
 Thank you for the comment. I am in USA and I need to also adjust
voltages from 0 to 20 kV. But using Tv is an interesting idea.

Couple of other points. What current do you require and how accurate
do you need the voltage or measurement to be? The HV probes are within
5% or so.

Hi voltage supply equipment which may be of interest to you is for
insulation testing, and surprisingly called ?insulation testers?.
Usually the voltages are predefined though. Do you require a variable
voltage or are a few ?spot? voltages OK ?

The TV voltage is fixed (more or less) but if you only require a very
low current you could hook up a resistor divider chain with high
voltage rated resistors -- high resistance too of course. Slight
annoyance is that the TV would still have to be run because the scan
coils are an integral part of the circuit.

If you can tell me your thoughts (not *all* of them) I can have a
browse on USA sites and see if anything comes up. Slight delay though
?cos I?m on GMT. And the real important question, what is your
preferred budget?

Best