New HV and HF probe design
Posted: Sat May 05, 2018 11:23 am
We got started talking over there but it fits better here if it should work - or for that matter fail spectacularly.
My basic first pass idea was to have a string of perhaps 10 meg resistors and somehow add a little capacity across each via the mechanical construction - perhaps round plates at each end of each resistor and all in a dielectric. For the simple 10x case with a 1 meg output and 25 pf (these might have to change to make the distributed caps reasonable), you'd have a 10 meg and 2.5pf element (R and C in parallel) in series with the 1 meg to the HV.
This should scale to any number of 10meg + 2.5 pf caps in series. It doesn't handle strays to the sides....I want to be able to put this inside an 8" or so ID shield along with other junk (the stepup xfrmr and so on) and get flat to say 20 mhz and down to DC (and I know a 10x is 9 megs and 1 meg, but here that sort of error we can just calibrate out).
My basic first pass idea was to have a string of perhaps 10 meg resistors and somehow add a little capacity across each via the mechanical construction - perhaps round plates at each end of each resistor and all in a dielectric. For the simple 10x case with a 1 meg output and 25 pf (these might have to change to make the distributed caps reasonable), you'd have a 10 meg and 2.5pf element (R and C in parallel) in series with the 1 meg to the HV.
This should scale to any number of 10meg + 2.5 pf caps in series. It doesn't handle strays to the sides....I want to be able to put this inside an 8" or so ID shield along with other junk (the stepup xfrmr and so on) and get flat to say 20 mhz and down to DC (and I know a 10x is 9 megs and 1 meg, but here that sort of error we can just calibrate out).