Modern digital oscilloscopes question

to

I used an old HP RF voltmeter in gradual school. The thing spat out

1/2 the line voltage onto the ground line. We had it floating and if I forgot to turn it off before changing the micorwave plumbing it would 'nibble' on my fingers to remind me. Really nice needle though!

George H.

The 610 uses a classic RCA small-signal mosfet in the front end. I got it on ebay for about $150. The manual says to replace the high-ohm resistors every *six months*. I checked it against various high-val resistors and it seems within 10% or so on the high ranges, pretty good considering how many 6-months have probably gone by so far.

John

George Herold a écrit :

Did once a 10^11 GBW preamp (100K-1MHz) with a 200pV/rtHz input noise down to 1.5nV/rtHz at 0.1Hz, has 140dB CMRR and still quite a lot (don't remember the figures) at 1MHz, a few years ago. It also show no thermal tail so that you can look at the nV level errors right after a 10V blast.

Maybe I should sell it too? Wonder what the market for this could be...

--
Thanks,
Fred.

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Nice! Paralleled BJT's on the input I assume. What was the current noise? Does it go below 100kHz?

I 'cheated' and used opamps. OPA288's at a gain of 10 they have a wiggle a bit beyond 2MHz, so I that's where I rolled 'em off. But very nice otherwise. Well 3nV of voltage noise, so not even close to 0.2nV

George H.

Schooling should be a gradual process ;-)

I still use an HP vector voltmeter.

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

A rare ability in this age of "lead people by the hand".

Give me knobs and switches over menu-driven crap every time ;-)

I intend to keep putting up with mine.

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

You, me, both.

-- "For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)

Walt: Daddy what's gradual school? T. S. Garp: What? Walt: Gradual school. Mommy say's she teaches at gradual school. T. S. Garp: Oh Gradual school is where you go to school and you gradually find out you don't want to go to school anymore.

-- Les Cargill

=A0 =A0(Richard Feynman)

Well for me, "It's called gradual school, becasue you gradually decide you don't want to be in school anymore."

George H.

Ah thanks, Now I know where I got it from.

It must of 'rang true' when I read it.

George H.

Well, it is hard to read a needle to 5 or 6 decimal places.

John

The original novel was from John Irving, who most seem to have forgot, and is always striking to read. Throw the original "Forrest Gump" on there, too.

-- Les Cargill

I figured it out before I went that far. Then I went back because I was being paid to go. I gradually came to the conclusion that I wasn't being paid enough. ;-)

But how often is that necessary?

I seldom need more than 3

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)