I have around 11000 volts DC voltge(very low Current in miliamp.)and i want to step down it into 48 volts DC?
Suggest me any method to convert it?
Also tell me how can i measure this high DC voltage & frequency perfectly?

 

An exotic voltage divider won't work? If you do it right, the output of the V/R will reflect the input.
If this is DC, where does the frequency come from?

 

Be interesting to know what type of equipment or circuit this is. My guess is it's Tesla coil related.

It will be difficult dropping that down since high megohm resistors are expensive and the resultant 48V would only be able to supply picoamps or you'd upset the divider.

Personally I'd scour eBay for a HV probe that's made to attach to a Fluke meter, or better yet an old KV probe used in the old TV repair days. This would provide you with, or with the start of, an accurate divider network.

Oh, and if there is any sort of frequency to it a capacitive divider could be made but 12 KV caps are even more expensive than high meg resistors.

 

Be interesting to know what type of equipment or circuit this is. My guess is it's Tesla coil related.

It will be difficult dropping that down since high megohm resistors are expensive and the resultant 48V would only be able to supply picoamps or you'd upset the divider.

Personally I'd scour eBay for a HV probe that's made to attach to a Fluke meter, or better yet an old KV probe used in the old TV repair days. This would provide you with, or with the start of, an accurate divider network.

Oh, and if there is any sort of frequency to it a capacitive divider could be made but 12 KV caps are even more expensive than high meg resistors.

Tesla is AC, this is DC.

What difference does it make if you roll your own voltage divider or buy a HV probe? They are both voltage dividers. 1% hi-meg resistors aren't prohibitively expensive and you'll know what your working with when you do it yourself..

Once again, this is DC, where's the frequency?

 

From Earth start with 12 turns of high current copper to a tap and then 910 turns ( better get a coil winding machine) of lower current enamelled copper wire. Use a small motor running a crank with one end of a 50cm or longer fiberglass pushrod and the other end has the connection to the top of your coil and a sparkgap to your 11000 volts DC. It should not make a physical connection to the high voltage. The crank must be spring loaded so that it stops with the spark gap wide open where it should not have an arc. Stainless steel balls are normally used for either side of the spark gap but beware of their capacitive attraction, because the spring load on the crank will need to be able to overcome that attraction but not strong enough to bog down the motor.

From the tap between the 12 turns of high current wire and the 910 turns of lower current wire you connect a diode with a filter capacitor oin the other side.

You then need a high voltage shutdown circuit basically a 48volt zener and resistor in parallel with the filter cap and a way to take current through that path and use it to signal a stop for the motor.

That is pretty low tech and brute force but it should work.