Sugestion for comparator

[i_build_stuff]

So, you're doing some kind of high energy discharge thing, and using your circuit to get precision measurements of the time when the cap voltage passes certain points? Or are you using it during the charge stage, so you know when to stop charging?

If it's the former, then you will probably want to use higher speed comparators, like the LM311.

Otherwise, the 741 would be fine.

You probably will want more resistance in the divider, though, as there's no reason for it to be dissipating anything on the order of 50W. You could use a divider that's more like 50M in series with 50k, as the output impedance will still be a bit under 50k. Then, you're using less than a watt.

I'd also go with what the other guys said, and string a bunch of resistors together in series to make the 50M--maybe 33 1.5M resistors and a 500k (they can all be 1/4 watt though) to keep them each at 200V.

 

[be80be]

I would use 1 of these

The CGH series resistors offer power ratings from 0.25 W to 5 W, and are available in resistance values ranging from 100 kΩ to 2000 MΩ at tolerances as low as &plusmn0.5 percent, and temperature coefficient of resistance (TCR) values down to &plusmn50 ppm/°C. Voltage rating ranges from 750 V to 20 KV.

if you put a bunch of them to make 50 Mohm it will be hard to insulate and most can't take the voltage

 

[Sceadwian]

The thing about resistors strung in series is the voltage is spread out evenly along the entire string, so you can use 200V resistors in a 50kv divider, you just have to use a lot of them =) You also need to insulate the leads between the resistors, but that can be as simple as dipping them in wax. The 50kv probe I saw on that site mentioned something about using solder bulbs as corona inhibitors but I'm not sure what it ment by solder bulbs. Corona discharge should be too much of a problem at only 2kv.

 

[be80be]

I no what saying but if he is not care full in making his divider He could very easily get hurt or killed

 

[Sceadwian]

Yep Be8 I know, I already warned him about that. (read previous posts)

 

[be80be]

Well then wax it up. You ask if I would use two resistors.I would if they are rated for the volts and 50 Mohm 2000 volt rated resistors is not going to ark over but some under rated wax covered can melt off and blow up in your face. That's why i said to be careful. One more time. If you made it out a bunch resistors dip it in varnish let it dry and do it about 10 more times.Or some high rated heat shrink tube.

 

[chemelec]

Instead of a Comparator, Why not just use an LM3914, (LED Driver) to show a Visual result of the Peak Voltage.
You can even Calibrate it to show those voltages that you want.

And if you want to get more complicated, you can create a Latch on each output, so your LED's stay Lit, Until Manually Reset.

Gary