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Registered Member #2470
Joined: Tue Nov 17 2009, 05:47AM
Location: Simi Valley, CA
Posts: 43
Hey, Ive got a pretty decent Tek 100 mHz O-scope here. I see lots of people looking at their tank circuits under the scope. My scope has a 400v peak for the waveform in. Do they use resistors in a chain, or are there scopes just rated for 20kV? I would really like to be able to see whats going on, since we have the technology to do it. As a coiler that's still learning, i think this would help me to really see whats going on in MY coil, not theoretically. Thanks, William
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
Hey.
They do use a resistive divider to read higher voltages. It is practically nothing but a chain of resistors.
But, the thing is, they use low tolerance resistors i am sure, and you also have to have a bypass capacitor in parallel with the diodes, which would equal the capacitance of the coax cable connecting it to the scope, to cancel out any capacitance.
This is not something i would suggest making of course, spending the extra money for the very expensive probe is better than killing your scope due to a project.
If measuring the current is all you want to do, such as the ringup and ringdown of the primary, a simple wide-band current transformer, is all you need. Just grab a couple ferrite toroids and wind 33 turns of wire on both, and cascade them for a ~1:1000 turn ratio. Then you use one turn from the primary (simply put a wire through a toroid for the single turn), and on the output side, use a 10 ohm resistor. For every 10 amps, you will read 100mv. Simple, eh?
Registered Member #2463
Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546
Be very aware that scopes and meters have a voltage derating factor when dealing with AC and DC mixed signal. Here is the curve for a TEK P106 probe used on TEK 7633.
The other interesting thing is 'windows' This term describes how many screens wide your scope can handle. Say you display 100 V P-P. a scope with 2 windows capability could handle a signal of 200 V P-P without clipping. By using vertical position, you could look at both parts. The only use for this is looking in the mud at the bottom of a very large pulse.
Rule: high voltage-high frequency-use someone else's equipment.
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Oscilloscopes
