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Why is it still necessary to worry about probing a floating ground?

Most digital scopes have power requirements like high-end laptops, so
why can't they have a battery option?

They all have plastic cases, so why can't they have isolated supplies
and no earth connection?


--
Defund the Thought Police

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On 3/26/21 4:51 PM, Tom Del Rosso wrote:
They all have plastic cases, so why can't they have isolated supplies
and no earth connection?

Because ungrounded equipment is always a bad idea.

--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com

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Tom Del Rosso wrote:
======================
Why is it still necessary to worry about probing a floating ground?

** Errr - user safety ?

Most digital scopes have power requirements like high-end laptops, so
why can't they have a battery option?


** Battery scopes are potentially lethal.

They all have plastic cases, so why can't they have isolated supplies
and no earth connection?

** BNC plugs are metal and so are accessory connectors on the front and back.

FYI

My 1987 analogue scope ( 10x8 cm, 50MHz, dual trace) draws the same power as my 1052E

...... Phil

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On 3/26/2021 2:51 PM, Tom Del Rosso wrote:
Why is it still necessary to worry about probing a floating ground?

Most digital scopes have power requirements like high-end laptops, so
why can't they have a battery option?

They all have plastic cases, so why can't they have isolated supplies
and no earth connection?

I believe that Tektronix still offers the TPS2000 Series.

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Phil Allison wrote:
======================
FYI

My 1987 analogue scope ( 10x8 cm, 50MHz, dual trace) draws the same power as my 1052E


** Just rechecked, the Rigol uses 18W and the trusty BWD 825 only 15.

It don't need a noisy fan either.


..... Phil

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RosemontCrest wrote:
--------------------------------------

They all have plastic cases, so why can't they have isolated supplies
and no earth connection?
I believe that Tektronix still offers the TPS2000 Series.

** Not the same idea and very exxe.

Float the DUT - not the damn scope.


..... Phil

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Phil Allison wrote:
================

My 1987 analogue scope ( 10x8 cm, 50MHz, dual trace) draws the same power as my 1052E

** Just rechecked, the Rigol uses 18W and the trusty BWD 825 only 15.


** Bugger - its a BWD 821

http://bee.mif.pg.gda.pl/ciasteczkow...wd_821_001.pdf

In 34 years of daily use, I have replaced 1 open 22kohm resistor and 1 pull switch mini pot.


...... Phil

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Well for one I think it voids most scope warranties.

Now look, floating the DUT makes much more sense, there are very very few instances where you have to create that hazard, and anywhere civilized with regulations on this **** will require your area to be cordoned off so people cannot wander in. Grounds can be a very complex topic.

Now one thing, if you find two 100WPC amps that are really fried out you can probably make an nice isolation transformer out of them. the voltage might not be perfect but god enough for testing.

Some people may disagree here, but once you re out of the hot side you no longer need the isolation. for example I am working on a Crown and it has a SMPS power supply. I have to fix that. then Iher a something little wrong in it and now I am working on the cold side. now as long as you have your wits, and are not going to fsall and drown in a bowl of soup (Mary Hartski) you know where the hot side is, if not forget working on this ****. Where the cord goes ??? MAYBE ?

I was working at a place, cement floor and on BIG TVs, many ties working on the floor. Well **** happened and I made them get an isolation transformer.. "You get a isolation transformer in here NOW. WHY ? If you don't I am going down to the hospital after a shock and claim I can never work in my field again for fear and sue you for every ****ing thing you got, BECAUSE YOU ARE SUPPOSED TO HAVE ONE !". Two days.

Th only time you really have to float the scope, and there are, if you are in an industrial setting working on ike Fanuc or some type of NC or CNC, or on something in the plant like some thing that controls motors n ****. the need COULD arise. But you are not doing that. If you were you would not be here asking.

In any unit you ever work on, of course if you have to work on the hot side get the transformer. And you make sure you know where the hot side is inside.

Enough for now. just find transformers at least six amps with secondaries adding up to the line voltage. Cheapest and easiest way.

Scope power
 

On Fri, 26 Mar 2021 17:51:59 -0400, "Tom Del Rosso"
wrote:

Why is it still necessary to worry about probing a floating ground?

Most digital scopes have power requirements like high-end laptops, so
why can't they have a battery option?

They all have plastic cases, so why can't they have isolated supplies
and no earth connection?

There are scopes with battery power. I bought the Owon DS8202 for that
reason, along with good memory depth.

It's just one way of increasing measurement flexibility and of
monitoring ground loop effects, but requires care in use.
Even low voltage circuits can present energy hazards to
technicians and their test equipment.

For AC measurements, ground is everywhere, so your isolation
should be limited to low frequency nodes.

Can't say much for the scope - it has the usual triggering and
noise issues as most of the present digital offerings.

The battery can be expected to last ~3yrs. I refurbed the pack
using cells from offshore and added a balancing circuit. Hopefully
this will increase their lifetime.

There are "handheld" scopes with internal batteries as well (Wave2).
These can make low-frequency monitoring a bit less invasive and
replace expensive differential probes, in some applications.

Holding them in any energised circuit application is not advised.

You need internal waveform memory to save data, if you want
to process it on a grounded PC, later.

RL



RL

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Phil Allison wrote:

** BNC plugs are metal and so are accessory connectors on the front
and back.

I get the point. Maybe not a problem with a single channel battery
scope.

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wrote:

Enough for now. just find transformers at least six amps with
secondaries adding up to the line voltage. Cheapest and easiest way.

Interesting...thanks.


--
Defund the Thought Police

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Tom Del Rosso wrote:

==================

** BNC plugs are metal and so are accessory connectors on the front
and back.

I get the point. Maybe not a problem with a single channel battery
scope.

** Like multimeter style scopes?

Hate them.


...... Phil

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Phil Allison wrote:
Phil Allison wrote:
================

My 1987 analogue scope ( 10x8 cm, 50MHz, dual trace) draws the same power as my 1052E

** Just rechecked, the Rigol uses 18W and the trusty BWD 825 only 15.


** Bugger - its a BWD 821

http://bee.mif.pg.gda.pl/ciasteczkow...wd_821_001.pdf

In 34 years of daily use, I have replaced 1 open 22kohm resistor and 1 pull switch mini pot.


..... Phil

but, but but, it's not capable of 3Ghz and sampling. It must be a useless
instrument.

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Cydrome Leader wrote:

===================

** Bugger - its a BWD 821

http://bee.mif.pg.gda.pl/ciasteczkow...wd_821_001.pdf

In 34 years of daily use, I have replaced 1 open 22kohm resistor and 1 pull switch mini pot.

but, but but, it's not capable of 3Ghz and sampling. It must be a useless
instrument.

** Very true.....

But I needed a scope for knock down, drag out service work on all kinds of items from
tube amps to 2kW SMPSs to 1kW linear mosfet power amplifiers.
Plus all the small stuff like condensor mics.
Plus I needed to be able to service it myself with readily available spares.
Plus it must have a mu-metal shield on the tube.

I was able to buy a spare, internal graticule, PDA CRT for it for under $200 - beautiful thing.
Eats the Rigol for breakfast for what I do.


....... Phil

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Phil Allison wrote:
Cydrome Leader wrote:

===================

** Bugger - its a BWD 821

http://bee.mif.pg.gda.pl/ciasteczkow...wd_821_001.pdf

In 34 years of daily use, I have replaced 1 open 22kohm resistor and 1 pull switch mini pot.

but, but but, it's not capable of 3Ghz and sampling. It must be a useless
instrument.

** Very true.....

But I needed a scope for knock down, drag out service work on all kinds of items from
tube amps to 2kW SMPSs to 1kW linear mosfet power amplifiers.
Plus all the small stuff like condensor mics.
Plus I needed to be able to service it myself with readily available spares.
Plus it must have a mu-metal shield on the tube.

I was able to buy a spare, internal graticule, PDA CRT for it for under $200 - beautiful thing.
Eats the Rigol for breakfast for what I do.

nice. How rare/common is the fancy shielding on a scope? I don't travel
with a scope so it's never been an issue for me.

A friend just got his first scope, some sort of mid 1980s Kenwood. He
emailed kenwood in japan and they send a scan of the manual. Sort of
jealous of it in fact.

Scope power
 

Cydrome Leader wrote:
====================

** Bugger - its a BWD 821

http://bee.mif.pg.gda.pl/ciasteczkow...wd_821_001.pdf

In 34 years of daily use, I have replaced 1 open 22kohm resistor and 1 pull switch mini pot.

but, but but, it's not capable of 3Ghz and sampling. It must be a useless
instrument.

** Very true.....

But I needed a scope for knock down, drag out service work on all kinds of items from
tube amps to 2kW SMPSs to 1kW linear mosfet power amplifiers.
Plus all the small stuff like condensor mics.
Plus I needed to be able to service it myself with readily available spares.
Plus it must have a mu-metal shield on the tube.

I was able to buy a spare, internal graticule, PDA CRT for it for under $200 - beautiful thing.
Eats the Rigol for breakfast for what I do.

nice. How rare/common is the fancy shielding on a scope?

** Low cost, Asian CRT scopes are unshielded.
Everything else pretty much is.


I don't travel with a scope so it's never been an issue for me.

** Got nothing to do with travelling.

A friend just got his first scope, some sort of mid 1980s Kenwood. He
emailed kenwood in japan and they send a scan of the manual. Sort of
jealous of it in fact.

** Likely has no mag shielding.

Be a real PITA if you locate a mains transformer anywhere near the tube.
Such scopes must be sited well away from the work bench and other items of test gear.

Or else the trace shimmers horribly at 50/60 Hz.
Major scam, IMO.


...... Phil