Re: 453 calibrator

Fabio Trevisan
 

Hey Jack,
Despite I'm member of this group for about 2 years, I consider myself still
a rookie about Tektronix stuff.
Specially because their product catalog is so small... What? Some 3
thousand items (just wildgueasing)?
To be honest, when I was writing that message, I even tried to browse
TekWiki for current probes, to see if I could corroborate my statements...
But I gave-up after having tried to open about 20 pages and not finding
anything.
But I really didn't know, as of my writing, if there was a real design
combining hall-effect and coil (now I know how to call it: a current
transformer)... I only suspected there could be something like that, as I
had a hunch that hall-effect devices would not get as high as 100MHz as I
knew there were current probes capable of that.
Rgrds,
Fabio

On May 13, 2018 4:28 PM, "Jack Wills" <jackduanewills@...> wrote:

You should be aware of a company called Tektronix, which makes the P6042
current probe.

DC-50Mz
Hall effect / coil

First offered in 1969!

I think you can find a manual on the web.

I have one and it works fine.

On Fri, May 11, 2018 at 2:58 PM, Fabio Trevisan <fabio.tr3visan@...>
wrote:


Hey Jeff,

Thanks for the heads up on my hunch about the possible construction of the
actual current probes...
I tend to concur with you, that being solid state-devices, there should be
at least some devices that can handle some high frequency.
But, as a a matter of fact, my knowledge in this area is an absolute zero.
The closest I was to a current scope probe was some 30 years ago in my
first job, but it belonged to the switching power supply folks (and I was
on the personal computer R&D dept) so, I had it in my hands and found it
beautiful how the clamp would slide open / close and how precise and
smooth
the movement was, and how polished the matching surfaces of the clamp
were.
I suppose that one really need to make sure the gap of the clamp is
consistent day in day out, for it not to interfere with the picked signal.
But as I read your message it got me curious. I googled a little bit on it
and got to these pages from TI:
http://www.ti.com/sensing-products/magnetic-sensors/
hall-effect/digital/products.html
http://www.ti.com/sensing-products/magnetic-sensors/
hall-effect/analog/products.html
At least from TI, the fastest ones are 30kHz and those are the digital
ones... the faster Linear ones (analog) are 20kHz... so it seems they're
not that fast after all (Granted... it may be only the TI range that is
narrow).
Anyway, I think it's conceivable to implement a hybrid design, mixing
Hall-Effect for DC response and DC stability, and magnetic pickup for
frequencies - say - above 10kHz, but I`m sure this is already invented
wheel and it can be probably seen on the service manuals of those probes.
By the way, since you mentioned Opto-Couplers... Not to counter your
thinking, but coincidentally supporting mine, I remember of having seen
once on eBay an Galvanically Isolated Tek probe (one that would allow up
to
some 1200V isolation IIRC), that would split the signal in two paths...
the
DC isolation path using optos up to some frequency and the AC isolation
path using a capacitive coupling, to allow the probe's claimed bandwidth
(I
think it was 20Mhz).
I can't recall what probe that was...

Rgrds,
Fabio



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