Oscilloscope with floating ground

Author Topic: Oscilloscope with floating ground - issues (Read 15358 times)

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darkspeed

Oscilloscope with floating ground - issues « on: 2010-06-02, 23:58:34 »

Newbie

Posts: 812

I am using a Bitscope DSO - it is a 9vdc powered unit it has provision for a system ground clip.

At the moment i do not have the system ground clip connected to the ground rod.

When i measure the bitscope probe lead with one channel of my 2465b i get 150vac
When i measure the bitscope ground clip of the probe with one channel of my 2465b i get 150vac
both ac wave forms are in pahse

When i connect the bitscope lead and clip i get a nice flat 0v and it measures everything correctly.

If i connect the system ground clip to the ground rod both the 150vac and the 150vac drop to 0vac

Ok.... so here is my question...

With the ungrounded bitscope i am able to measure a very interesting result from a coil - when the bitscope is grounded this effect goes away

So either the effect can not present itself when one side of the coil is grounded ( through the probe ground clip ) or it is some anomalie in the bitscope itself

I have reason to believe the effect wont present itself with one side of the coil grounded - but i am conflicted

I need to buy a non pc DSO

BEP	Re: Oscilloscope with floating ground - issues « Reply #1 on: 2010-06-03, 03:48:58 »
Newbie Posts: 2205	What you describe is just as easily found when using a variety of scope types. Your best bet, likely the least expensive, is to insert an isolation transformer between your PC and the wall socket. These interesting artifacts usually aren't interesting when wiring issues are corrected, grounds being one of the first to correct.

darkspeed

Re: Oscilloscope with floating ground - issues « Reply #2 on: 2010-06-03, 09:05:00 »

Newbie

Posts: 812

Thanks WW.

I can see it faintly on my 2465b but not as well as the non grounded bitscope..

So... if we are in the business of collecting and modulating ambient energy in the big capacitor we call earth and sky...

What is a proven method of measuring a pulse " disturbance in a static field " not in relationship to ground

i.e. how do you measure your " static " electrons on your coil if your ground wire never allows them to accumulate ..

thanks..

Peterae	Re: Oscilloscope with floating ground - issues « Reply #3 on: 2010-06-03, 09:48:22 »
Group: Administrator Hero Member Posts: 4637	This may seem like a silly answer, but depending on the anomaly, could you build an anomaly detector and forget the scope and see if you can detect the event without any outside connection, or use a battery powered laptop, although i am having problems as well in this area.

BEP

Re: Oscilloscope with floating ground - issues « Reply #4 on: 2010-06-03, 13:19:39 »

Newbie

Posts: 2205

Quote from: darkspeed on 2010-06-03, 09:05:00

Thanks WW.

I can see it faintly on my 2465b but not as well as the non grounded bitscope..

So... if we are in the business of collecting and modulating ambient energy in the big capacitor we call earth and sky...

What is a proven method of measuring a pulse " disturbance in a static field " not in relationship to ground

i.e. how do you measure your " static " electrons on your coil if your ground wire never allows them to accumulate ..

thanks..

A variation of this circuit may be a good idea.
http://www.ece.rochester.edu/~jones/demos/ahern.html

Using this > http://amasci.com/emotor/chargdet.html < as the front-end to a scope probe might be useful.

Grumpy

Re: Oscilloscope with floating ground - issues « Reply #5 on: 2010-06-03, 15:03:14 »

Group: Tinkerer
Hero Member

Posts: 4265
tExB=qr

Quote from: darkspeed on 2010-06-03, 09:05:00

Thanks WW.

I can see it faintly on my 2465b but not as well as the non grounded bitscope..

So... if we are in the business of collecting and modulating ambient energy in the big capacitor we call earth and sky...

What is a proven method of measuring a pulse " disturbance in a static field " not in relationship to ground

i.e. how do you measure your " static " electrons on your coil if your ground wire never allows them to accumulate ..

thanks..

displacement current sensor

http://www.overunityresearch.com/index.php?topic=79.msg3505#msg3505

alternate would be a VTVM connected to a "detector" made from a flat plate surrounded by a cylinder with a mesh cover at one end and the plate at the opposite end. See attached: Use coax instead of the separate wires that I initially used.

You can see the disturbence on any insulated conducting object, but the charge is quickly lost.

A better "detector" would be one that actually converted the surface charge of the displacement current into a conduction current. For this you need a magnetic field perpendicular to the applied force from the pulse and the detect positioned in the correct orientation to get a particle precession in the detector circuit.

SIDE NOTE:
you can shield with static fields if the fields are strong enough to prevent the items within the field from being re-polarized by the energy you wish to shield from.

This all stems from antenna theory, by the way.

Some interesting reading: http://espace.library.uq.edu.au/eserv/UQ:9792/saha-edwards-aup.pdf

Oscilloscope with floating ground - issues

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Oscilloscope with floating ground - issues

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Oscilloscope with floating ground - issues

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darkspeed	Re: Oscilloscope with floating ground - issues « Reply #6 on: 2010-06-03, 19:54:02 »
Newbie Posts: 812	Thanks guys, i may have to build one of those.. What about the portable DSO's that run on a battery pack like the Tektronix TDS 2012 or 3032? How do they reference ground The effect i am detecting causes a coil to ring down at its natural resonant frequency from a sharp pulse, its not some random noise, so im hoping it is for real

Grumpy

Re: Oscilloscope with floating ground - issues « Reply #7 on: 2010-06-03, 20:14:45 »

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Posts: 4265
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Quote from: darkspeed on 2010-06-03, 19:54:02

Thanks guys, i may have to build one of those..

What about the portable DSO's that run on a battery pack like the Tektronix TDS 2012 or 3032? How do they reference ground

The effect i am detecting causes a coil to ring down at its natural resonant frequency from a sharp pulse, its not some random noise, so im hoping it is for real

One other way that hasn't been meantioned yet is to charge a capacitor to a few tens of volts, add a length of coiled wire to each terminal of the cap and then mesure with a VTVM while the influencing effect is active. Cap will increase in charge if force is unidirectional and oscillate if force is back and forth.

Or, cutting to the chase with brute force, just pull an arc off the ringing coil with a conductive object.

We are all moving the medium around, just not converting it.

darkspeed	Re: Oscilloscope with floating ground - issues « Reply #8 on: 2010-06-03, 20:30:15 »
Newbie Posts: 812	I did build a fast diode full bridge with a small cap in the center and it charges the cap - but there is a problem - because of the 60cycle influence on the bitscope when i connect the bitscope to the coil side of the bridge there is some voltage injection into the cap from the bitscope - grrrrr.