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Registered Member #135
Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735
Here is something I worked on today and finished. It's a common mode and differential mode voltage divider! It's really neat! It's 2 dividers in one package case grounded, but with a twist. You get a differential divider that's ground lifted from the case, summing both divided hots for easy measurement! I aligned it today with my HT probe and couldn't help but laugh in joy as it actually works! Measured ~7KV on each leg, and ~13KV through the differential output. A must have for voltage and current measurements for any coiler!
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Looks good.
From the photos, it appears to be a capactive divider only. Is this correct? If so, you should put resistors in parallel as well with each capacitor so that you get a more flat response from DC up to your AC end.
Here is one of the high bandwidth dividers i built a few years ago. This divider is good for 60kV and works extremely well - frequency response almost completely flat across the band out to about 50Mhz.
Registered Member #135
Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735
The very last stage has an adj. pot so I can calibrate better. Otherwise the output on the bottom with the caps I chose was way too high, like 90VAC. So with the pot I got it down which works for me for now.
I want to do what you have on your page because that's a really sweet divider. At this time I'm not really sure what R value to use because I'm pretty new to the dividers. This one is just a capacitive divider. I have the right value for my calculations, but they were removed from boards so their leads are too short, and this is just a bodge-job to get me on my feet. I'll look into getting some really high value resistors eventually.
The goal though is that with the two dividers I can get terminal voltage at the one AND measure the voltage drop through the protective load (1500R 50W) so I know the current, that's the key! Voltage and Current at the same time!
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
What are your goals for your divider design (i.e. bandwidth you wish to measure?) Also, i'm not sure i follow you on how you are measuring current - do you have a diagram or something that can explain this better?
Registered Member #135
Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735
Current measurment is just the proportional drop across the two terminals through the 1500 ohm load resistor. This should be 90*root2 / 1500 = 60mA AC and 90 Volts being the meter reading.
Registered Member #135
Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735
wave...forms.......aaaahhhh...... scratches head I'll work on it. It's not like I don't have a scope, or a good scope, its just that getting a capture of the waveform isn't a simple task for me. The last time I tried with the digital camera i only got part of the sweep. I dunno about a DSO. I might be able to find one at the swapmeet sometime soon, but the money is kinda an issure at this time.
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Wow, i've never had that problem before. You must have a pretty old oscilloscope. Of course, now that i remember, i took shots of my oscilloscope after the waveform was captured in storage (digital scope) so i honestly never tried taking a shot with it continuously sweeping . . .
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Voltage Divider
