Voltage divider for high volt measurement

Lexmark laser printers use 15 kV on the drums and use a sine wave stepup signal transformer to create this then rectify and regulate with a long string of 1/4W 10M~100M resistors back to an LM324 to regulate the output like AGC. You can string these inside a DIY plastic wand with a reinforced tip with a total R of 1 GOhm and make this suitable for measuring 50 kV using 1kV/mm for a clean wand with air at 3kV/mm. Surface contamination reduces the withstanding voltage.

Now you can get 1Gohm HV resistors at low cost in stock so you may use fewer in a string https://www.digikey.ca/en/products/detail/te-connectivity-passive-product/RGP0207CHK1G0/2389890



When we used these in the 80's outside a clean room to generate ions with needle inside a 1cm half cup, they created so much RF that it interfered with our magnetic servo writers inside the clean room (for HDD Mfg) , so I asked maintenance to remove it.

Thanks for the reply, what would this give me as a reduction factor? 10:1, 20:1, 50:1 ?
So I assume a standard 2 resistor VD is not a safe idea?

Not unless you have a long expensive resistor...

If you measure your DMM impedance it may be 1 Meg or 10 Meg then 1Gig is 100:1 ratio and < 1W dissipation (V^2/R)

the spec sheet says:
DCv = 20k ohm/V input resistance

then you choose max scale and use that V * 20k = Rin for the analog meter but use that to measure the DMM on 600 V scale so that 200V = 20 kV using 99:1 R ratios for 100:1 or whatever you prefer.

Wait, you lost me.....
use what voltage?

those specs were for my analog meter. Digital meter is 600V max / 10M impedance

Yes Whatever voltage scale your analog meter is multiple by 20k is it's input resistance while the DMM is 10M

I forget what Analog Vdc scales are used in Simpson meters and you didn't specify.. So if you used a series string and a shunt in parallel with meter, you have to compute the new ratio or tell me the voltage and thus the resistance to know what you need

Ok, so sticking with the 600v / 10M DMM........
The generator has a range of 15k - 20k output. Since I have no idea if its already set at Max or not. I need to protect the meter while dialing it down, or up as the case may be.