"Straydog" wrote in message...

Do you know what the term "parasitic" means as it applies to chips?


And I thought it was all about microbes, barnacles, and other blood suckers.

"Straydog" wrote in message
.com...
Are you talking about any PC _sound_card?

The fact that you even ask that shows how little you know about them.
However some like the Lynx compare pretty well to an AP test set within
their designed range, for a LOT less money.

A PC _sound_card? Meant for _audio_ frequency ranges?

Yes, amazing isn't it that is exactly what audio people want to measure, but
try 1Hz to 90kHz for some sound cards, with 0.001% N+D.

You think I'd rather have that than a decent DC to RF (X
mHz) oscilloscope 10 v/div down to 1-10 mv/div sensitivity?

**** just about any sound card can do that voltage range with a 20 cent
resistive divider. Shame you didn't mention the real problem, if you want a
high input impedance you need a high quality buffer amp. Of course those
simply measuring audio gear don't need it.

Time base
seconds/div to microseconds/div or less? And, can measure DC. Maybe if
you want to do some FFT or other DSP on an audio signal you can have the
soundcard. I'll pick the dedicated gear with specs that fit the ap.

Good for you, especially if your application is not audio. Funny though how
most dedicated test gear is connected to a PC data aquisition system these
days, at least in most metrology labs. The ability to make repeated
measurements unattended, with data manipulation, analysis and presentation
is something not many labs would be without anymore.

You mean you don't need to _assume_ the soundcard is working or you don't
need to worry about sw bugs or invalid process or tollerances or other
spec-dependent limitations? So, if the computer says "X" then it is
absolutely true, valid, straight from the horses mouth? No ands, ifs, or
buts? Do you know what the term "parasitic" means as it applies to chips?

Calibration standards apply to ANY test gear, analog or digital, PC based or
stand alone.
Anybody with knowledge of metrology understands how to make proper
measurements, those who don't believe their test gear's badge is all the
calibration that's necessary :-(

MrT.

Straydog wrote:



On Mon, 27 Nov 2006, Les Cargill wrote:

Bret Ludwig wrote:

Arny Krueger wrote:

snip

You can find an audio interface that will outperform say a HP 334
for $30.
For $200 you're in the same league as some of the older, but not all
that
old AP stuff.



Trying to use a PC as a general purpose bench instrument is like the
old race car guys that I used to hang out with. They would build a new
big block Chevy and a Turbo 400 behind it every couple of seasons. They
put in a dually one ton truck and pulled a trailer that would have been
just about right for an old single axle B Mack around for the season.
They got about five miles to the gallon under load too.

When I got older, I'd ask them why they didn't buy a real truck, you
know, air brakes, Fuller Roadranger, like a used Yellow or Roadway day
truck. Well, license and insurance cost too much and you needed a
"chauffeurs license" to drive it. (Those pre-CDL days!)

Well okay, at least put a diesel and an Allison in the pickup, why
don't you? Because we don't know how to work on them and you can't get
them in the junkyard for a hundred bucks.

Eventually they got tired of building "motors" (sic) for the tow truck
and not the race car and put a 3208 Cat or a turbo 4-53 and an Allison
or a Clark five speed in there. They then got like ten miles to the
galllon and the truck rusted out twenty years later and the engine and
trans still ran.

The PC does okay as a controller or as a dedicated production test box
with a buffered, isolated interface. But it is not like a scope or gen
or analyzer that sits on the bench.


*If* the thing under test is amenable to it, there's little
or no hope of improving on a PC soundcard


Are you talking about any PC _sound_card?


Yes.

and Matlab as a combo. Might

need a breadboard to adapt the signals, but if it's in range,
it'll outrun just about anything for the money.


A PC _sound_card? Meant for _audio_ frequency ranges? Like single diget
Hz to 20-30 kHz? You think I'd rather have that than a decent DC to RF
(X mHz) oscilloscope 10 v/div down to 1-10 mv/div sensitivity? Time base
seconds/div to microseconds/div or less? And, can measure DC. Maybe if
you want to do some FFT or other DSP on an audio signal you can have the
soundcard. I'll pick the dedicated gear with specs that fit the ap.

You're assuming you can trust the test equipment. Sometimes,
you can't....


You mean you don't need to _assume_ the soundcard is working or you
don't need to worry about sw bugs or invalid process or tollerances or
other spec-dependent limitations? So, if the computer says "X" then it
is absolutely true, valid, straight from the horses mouth? No ands, ifs,
or buts? Do you know what the term "parasitic" means as it applies to
chips?


Absolutely. *In this case*, the rig beat out some rather expensive
specialized test gear. We also needed several hours of captured data.

We had eight or nine scopes and three logic analyzers; the PC
complemented 'em nicely. What works depends on the test.



--
Les Cargill


--
Les Cargill

"Straydog" wrote in message
.com

*If* the thing under test is amenable to it, there's
little or no hope of improving on a PC soundcard

Are you talking about any PC _sound_card?

Let's put it this way. A lot of good audio development and test was done
with equipment such as the HP 333/334. Conventional wisdom is that if you
can't measure it with a 333, you can't hear it either. A 333 pretty well
ran out of gas around 0.02% THD. IOW if you hooked a perfect signal source
up to a 333 and nulled it carefully, that would be a good residual. The
residual THD of a typical Realtek audio interface on a modern motherboard is
less than that.

and Matlab as a combo. Might
need a breadboard to adapt the signals, but if it's in
range, it'll outrun just about anything for the money.

All you need is a a modern PC and a freeware audio testing program - RMA55.

A PC _sound_card? Meant for _audio_ frequency ranges?

Unh huh.

Like single diget Hz to 20-30 kHz?

Well up to 20 KHz or so.

You think I'd rather
have that than a decent DC to RF (X mHz) oscilloscope 10
v/div down to 1-10 mv/div sensitivity?

Try verifying the specs of a $39.95 DVD players audio outputs with a scope.

In the real world of general purpose troubleshooting and development you
would ideally have both.

And, can measure DC.

That's what voltmeters are for, chum.

Maybe if you want to do some FFT or other DSP on an
audio signal you can have the soundcard.

You seem to be seeing the light.

I'll pick the dedicated gear with specs that fit the ap.

Of course.

You're assuming you can trust the test equipment.
Sometimes, you can't....

You mean you don't need to _assume_ the soundcard is
working or you don't need to worry about sw bugs or
invalid process or tollerances or other spec-dependent
limitations? So, if the computer says "X" then it is
absolutely true, valid, straight from the horses mouth?

Measurements are what they are. Their utility is always in the
interpretation.

No ands, ifs, or buts? Do you know what the term
"parasitic" means as it applies to chips?

It means, "Where is my dual-trace scope?"