According to this part, it seemed possible that the OP (or possibly other
readers) may be inclined to do something risky.. even though earlier replies
recommended proper safe procedures (and the reasons for them)..
*** No question about the scope being grounded, no one suggested
otherwise. Tektronix maintain that floating measurements, taken in a
DUT powered by an isolating transformer, is bad practice. ***

Using a scope in the conventional/safe manner (earth grounded power cord),
on a Hot circuit (primary side of a SMPS) without proper isolation IS bad
practice, no question.
I know you knew that, Arfa.

So, that just takes the subject back to using a proper dual-trace model with
suitable input capacity, and a Differential Mode or Add feature described in
the scope's operation manual.. *or* using a proper isolation xfmr between
the utility power source and the DUT (device under test).

My opinion is that using a proper I-T is the best overall solution.

BTW, it hasn't been mentioned yet, so I'll throw it in here..
A properly isolated DUT is safe in terms of there is no path to the utility
power source for the test equipment or the operator/user to accidently come
in contact with.
That doesn't mean that the operator is fully safe from electrical shocks or
electrocution, if one is careless.

The 'one hand rule' is safe practice.

There can be high voltage potentials and sources of current within the DUT
to present hazards for the tech/equipment operator.
Safe practices are still required, even though the threat of having
line-sourced current pass thru the operator to earth ground is eliminated,
the DUT when powered may still be capable of injuring the operator/tech.

Safety information is covered in the Repair FAQ
http://www.repairfaq.org/


--
Cheers,
WB
..............


"Arfa Daily" wrote in message
...


"Wild_Bill" wrote in message
...
It's not clear what you're after (echo).

For most technicians, the term "floating" in connection with scope use,
refers to 'floating the scope' which means:
Read This Part separation of the scope power cord's 3rd pin from earth
ground.

I didn't look at Tek's cautions/recommendations, but I know scope
manufacturers are familiar with the (nearly always) ill-advised practice
of Floating A Scope.

Are you unfamiliar with proper and safe practices, or unfamiliar with
using a scope, or unable to express what it is you want ask about?
All of the above?

I'm fairly certain that all of Tek's recommended procedures are safe..
maybe you're just not understanding what's presented in the literature..
or maybe you're trying to apply the wrong procedure for your intended
purpose.

As far as various types of electronic gear/equipment go, it's very common
that there are floating voltages present inside them.

No one was placed here to try to understand what you meant, even though
you didn't say it.

Maybe you were thinking of sci.telepathic.electronics.

--
Cheers,
WB
.............

The OP was very clear in what he wanted to do i.e. make scope measurements
on the primary side of a non isolated switcher. The only 'problem' was
that he misinterpreted what had been said in a Tek application note, which
he now understands correctly for what it was. I have seen no indication
that he is incompetent at using a scope or understanding safety procedures
anywhere in his post or various replies. He has merely asked for what
people on here who are involved in this type of work, recommend in terms
of safe practice from both a personal injury and equipment damage point of
view. There has been a consensus expressed, and as far as I can see, he
accepts and fully understands what he has been advised.

Arfa