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High voltage probe for O-scope, 1 of 2, ( DEVELOPMENT ).

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teravolt

Tue Apr 12 2011, 07:34PM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

I asume you want a high z of about 10-100Mohm probe impedance. it seems to me that you want a scpoe probe that has at least a 5Mhz bandwidth with a hi Z input. how many volts do you want to measure at the most

Patrick

Wed Apr 13 2011, 01:11AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

teravolt wrote ...

I asume you want a high z of about 10-100Mohm probe impedance. it seems to me that you want a scpoe probe that has at least a 5Mhz bandwidth with a hi Z input. how many volts do you want to measure at the most

Input would be 375Mohms, (10,000:1 or 1000:1) @ 41kV pk DC.

teravolt

Wed Apr 13 2011, 07:39PM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

Hi Patrick, what you are trying to do is not a easy task most High Z probes have e some sort of compinsation at the scope. the higher the probe resistance the harder it will be to get a better frequency response. with that a better aproch is to design your probe around your application of want to mesure the voltage on your primary you will know that it will be a high voltage but a low resistance so you could use a probe made out carbon comps say with a Z of 1Mohm with some amount of parallel capacitance like in the picture at the beginig of this thread. if you are gong to look at your SMPS a simple divider with a little capacitance at the base resistor may be all you need. that the way I would aproch it. I would like to make a differensial HV probe for the scope. probes like tecktronix are expensive because of the reserch that you are doing now so some one has allready done it with a lot of efort

teravolt

Thu Apr 14 2011, 04:58AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

hears another exmple of this type of probe

Patrick

Thu Apr 14 2011, 05:31AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Have you seen this?

I would like to get that type, in my hands to test, but i dont think i can settle for just what you describe. I need a tek, North star or ross enginneering one to look at, internally. I really need to replicate their type of probes.

teravolt

Thu Apr 14 2011, 02:12PM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

the devider probe part is easy it is the compinsation box at the o-scope end is the kicker

Patrick

Thu Apr 14 2011, 04:35PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

teravolt wrote ...

the devider probe part is easy it is the compinsation box at the o-scope end is the kicker

well ok, in simulation i have had wild variation in any of the compensation techniques i have attempted, so i have taken a normal 10X probe and connected that to the bottom of the divider, why wouldnt this work? it seems like it should.

the HV probe itself is 1,000:1 while in series with a X10 probe, the total divsion ratio then becomes 10,000:1.

Yellow are copper "Park-like" Caps, Red are resistors. The bottom most section are where compensation and LV componets live.

look here, internals of a P6013A, schematic and disassembeld

And here, look at my northstar email qoute.

EDIT: remember, the NorthStars and others now have a factory calibration inside the probe that the end user cant change. And a single capacitor trim on the BNC end to scope. These are far improved from the defuct P6013A (or the P6014, P6015) that have which has 6 (and 8) adjustments all freq related.

Patrick

Sat Apr 16 2011, 06:46AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

I found this:

"Dan (or the Captain) just made a home brew probe that was extremely
interesting and had some modern design techniques behind it!! I wound not
be surprised if it easily outperformed the P6015...

Cheers, Terry "

Im still trying to find "Dan the Captain's" work.

Pinky's Brain

Sat Apr 16 2011, 01:58PM

Registered Member #2901 Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837

He was at Eastern Voltage Research I see ... they had a HV divider on the old website resources, but that is no longer there. I don't remember exactly what was on the page and the wayback machine isn't cooperating. They do have schematics for a high voltage probe. Of course a physical description is more important than the schematic with just electronic components, but it's something :

Here is the original wayback machine page describing the divider, unfortunately the pictures have been lost to time :

teravolt

Sat Apr 16 2011, 05:10PM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

Hi Patrick, I found some links that might be helpfull

let us know what you think

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