Rigol caught with their pants down! (DS1052E Oscilloscope) - Page 2

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Re: Rigol caught with their pants down! (DS1052E Oscilloscope)



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Umm, no. Ever heard of Nyquist?

Plus to see anything like a signal for your eye's benefit, you're better
off with x10 sampling.

So 100MHz is more on the mark. Does it allow you to simply plot the points
without the "join the dots"?

BTW if you had exactly 1GHz going in, and it manged to sneak pass the front
end, you'd end up with a straight line at some DC level.

Ray

Re: Rigol caught with their pants down! (DS1052E Oscilloscope)


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Yep. You can choose between dots, linear ("join the dots") vector
intepolation, or sinX/x interpolation.

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That would be a neat trick!

Dave.

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Re: Rigol caught with their pants down! (DS1052E Oscilloscope)


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I have heard of Nyquist, just forgot to apply him in this case :)
There will be an anti aliasing filter in the front end so you wont see
much if you put in anything close to half the sampling rate = 500Mhz.
Or maybe Rigol has decided to cut corners and got rid of it
completely ;)




Re: Rigol caught with their pants down! (DS1052E Oscilloscope)


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and you forgot about the analog bandwidth too, that's kinda important!

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Err, the front end bandwidth is only 50MHz!
Kinda hard for any signals higher than that to sneak past, as Ray said.

Dave.

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Re: Rigol caught with their pants down! (DS1052E Oscilloscope)


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Yes, but that's the 3dB bandwidth, isn't it? i.e the frequency at
which the voltage is 1/sqrt2 that of its value at DC. Hence you should
still be able to see signals higher than 50Mhz. Plonk a signal
generator on it and tell us what you you see ;)


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Re: Rigol caught with their pants down! (DS1052E Oscilloscope)



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snipped-for-privacy@s31g2000yqs.googlegroups.c
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Anti aliasing filters do not have to be purely low pass filters set
below the Nyquist frequency.
You can also use band pass filters to digitise a frequency above Nyquist
or even HIGHER than the sampling frequency.

You will not get the original signal, but you will get an undersampled
signal that still can be used in certain applications such as digital
receivers sampling off IF chains.

The important part of the filter design is to have very good rejection
of signals outside the designed centre frequency so no signals present
at the usual "baseband" are present.

Obviously the ADC must be capable of functioning at the desired input
frequency.

It works, and is quite commmon.

Ray

Re: Rigol caught with their pants down! (DS1052E Oscilloscope)


On Mon, 20 Jul 2009 08:02:20 +1000, "David L. Jones"

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We overclock/overstress parts when there's a substantial payoff. One
Freescale uP is rated for 16 MHz clock, actually gets wonky at 44, so
we run it at 20. One microwave schottky diode is rated for 2 volts
reverse, leaks a bit at 7, so we use it at 4. Adding a heatsink to an
FPGA can buy some timing margin. Some diodes and cmos parts leak four
or five orders of magnitide less than the datasheet guarantees. An
0603 resistor can dissipate a quarter of a watt safely. The trick is
to take calibrated risks where there's demonstrated margin and big
paybacks, and take zero risk everywhere else.

John


Re: Rigol caught with their pants down! (DS1052E Oscilloscope)


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Doesn't the manufacturer sort of put themselves at risk that the chip
vendor decides to change the process or ship marginal product ("Nobody
is buying our 100 MHz parts anymore, so we will save a few bucks and
make and ship 40 MHz parts (that pass only to 45 MHz)")?

--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©

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Re: Rigol caught with their pants down! (DS1052E Oscilloscope)



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Yep. That's what I would be extremely concerned about. If I ever decided to
run a part over its rated limits (speed wise), I would put in hooks, for
production testing, to lower its supplies to their minimum and then run
those tests at the maximum rated d.u.t. temperature.

Of course, in Larkin's case, the only person that can fire him for non
performance and insubordination is his wife.

Bob
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Re: Rigol caught with their pants down! (DS1052E Oscilloscope)


On Mon, 20 Jul 2009 11:00:40 -0700, "BobW"

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Hey, nowadays I report to The Brat.

John


Re: Rigol caught with their pants down! (DS1052E Oscilloscope)


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I was just going to say, didn't she show an interest in the biz lately
and even do a layout? Remember, she may one day be the one deciding
which nursing home you guys go to ;-)

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http://www.analogconsultants.com /

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Re: Rigol caught with their pants down! (DS1052E Oscilloscope)



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She is doing all our PCB layouts and managing engineering [1]. And
doing all our press releases. Not bad for a 22-yo with a minior in
psychology and majors in softball and beer pong.

I asked her a couple of months ago, "Say, do you want this company?"
She thought about it for a few hundred milliseconds and said yes.

John


[1] And she does my schematic entry for me. I still draw pencil on
blue-grid D-size vellum.



Re: Rigol caught with their pants down! (DS1052E Oscilloscope)


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[...]

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Great. I remember a few years ago when you hinted that there wasn't much
hope she'd jump in. For a friend of mine that turned out to be the case.
One of their daughters would have the technical knack to run his
business but it seems she's not very interested. Similar age.

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I do that less and less. Most of the time when a client needs a
re-design I fire up the WP and CAD and have at it. Except when at the
pool, like 30 minutes ago. Two Clearprint 1000HP-4 vellum pads always at
the ready.

--
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http://www.analogconsultants.com /

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Re: Rigol caught with their pants down! (DS1052E Oscilloscope)


On Mon, 20 Jul 2009 13:40:41 -0400, RFI-EMI-GUY

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Sure. Life is risky. Given a product with 200 different parts, two of
which are overstressed, there's probably more risk that one of the 198
other parts will be EOL'd.

John


Re: Rigol caught with their pants down! (DS1052E Oscilloscope)


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Have you ever been caught in the situation of one of your over-stressed parts
being changed by the manufacturer in such a way so as to render it unsuitable
for your needs?



Re: Rigol caught with their pants down! (DS1052E Oscilloscope)


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Happened to another engineer: Bought tons of 5% capacitors for
production, went into Hilbert shifters. They always hand-picked the 1%
parts out of this lot and used the rest for jelly-bean stuffing. One
balmy summer day they found the first shipment that had a hole smack in
the middle of the Gaussian tolerance curve. Obviously someone had
detected a business opprotunity ... whoops.

--
Regards, Joerg

http://www.analogconsultants.com /

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Re: Rigol caught with their pants down! (DS1052E Oscilloscope)


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Sure production ends on the part and then they look in the stockroom and
find a dusty box of parts, where did they come from? Probably someone
else hand picked parts and sent the rest back for restock!

--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©

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Re: Rigol caught with their pants down! (DS1052E Oscilloscope)


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They couldn't be that brazen unless they'd have gone to great lengths
such as re-belting them all. Because the good ones weren't all in front
section.

--
Regards, Joerg

http://www.analogconsultants.com /

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Re: Rigol caught with their pants down! (DS1052E Oscilloscope)



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Not to be too picky, but why would production end on a profitable 5%
parts line?
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Likely selected out before packaging.

Re: Rigol caught with their pants down! (DS1052E Oscilloscope)


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He meant by a customer who then sent it back. If the manufacturer did
that there would be no re-stocking process, they do it right off the
conveyor belt.

--
Regards, Joerg

http://www.analogconsultants.com /

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