Modern digital oscilloscopes question

[eatmorepies]

Hello

I worked in a place that gave me access to budget, non memory 20MHz CRT
scopes - I no longer work there. They were perfect for my needs.

Six years on and I find I need an oscilloscope, the market seems to have
changed. Are those cheap digital models any good?

I need reasonable Y sensitivity (5mV/div), up to 5MHz, storage would be
nice, it's not for radio work.

I found things like this...

http://www.rapidonline.com/Tools-Eq...399/?sid=2e6f6286-b98a-4994-b9ce-0631e8fc6b4d

Decent for the money? Or to be avoided?

John

 

[Phil Allison]

"eatmorepies"

I worked in a place that gave me access to budget, non memory 20MHz CRT
scopes - I no longer work there. They were perfect for my needs.

Six years on and I find I need an oscilloscope, the market seems to have
changed. Are those cheap digital models any good?

** Not so good for service work, particularly audio service.

If you like using analogue scopes, stick with one.

Analogue scopes are easy to use and tell you no lies.

The opposite is true for digital ones.



.... Phil

 

[Phil Allison]

"George Herold"

Yeah but an analog 'scope can't average.

** So fucking what ?

Put that together with the digital filters on the front end of the
Rigol

** Shame there are no analogue ones.

Shame how the scope keeps showing things that are not at the input - like
aliasing products, noise and signals that have stopped seconds ago.

These are fatal flaws in audio servicing.


.... Phil

 

[Phil Allison]

"George Herold"

Yeah but an analog 'scope can't average.

** So fucking what ?

I'll post some 'scope shots tomorrow.


** FFS dickwad - I own a bloody Rigol !!!

Put that together with the digital filters on the front end of the
Rigol

** Shame there are no analogue ones.

Oh I agree, But the cost would be out of control.


** Not to mention the scope would then finally,y actually have
INTENTIONALLY varying bandwidth with sweep setting.

This is the biggest LIE about DSOs and why analogue scopes are SOOOOO much
better for troubleshooting analogue circuits.

Shame how the scope keeps showing things that are not at the input - like
aliasing products, noise and signals that have stopped seconds ago.

These are fatal flaws in audio servicing.

Oh DSO's aren't for every task.


** FFS read the bloody CONTEXT !!

Here it is again - you RETARDED BIRD BRAIN !!


" I need reasonable Y sensitivity (5mV/div), up to 5MHz, storage would be
nice, it's not for radio work.

** Not so good for service work, particularly audio service.

If you like using analogue scopes, stick with one.

Analogue scopes are easy to use and tell you no lies.

The opposite is true for digital ones."



.... Phil

 

[Bob Masta]

Hello

I worked in a place that gave me access to budget, non memory 20MHz CRT
scopes - I no longer work there. They were perfect for my needs.

Six years on and I find I need an oscilloscope, the market seems to have
changed. Are those cheap digital models any good?

I need reasonable Y sensitivity (5mV/div), up to 5MHz, storage would be
nice, it's not for radio work.

<Shameless plug>
How about a cheap analog scope, supplemented by a
ridiculously-cheap (US$29) Windows sound card scope for
audio work?

Sound cards don't do DC (without mods or external help), but
the "audio" range keeps creeping up... these days you can
get to nearly 96 kHz (192 kHz sample rates) even on cheap
built-in sound chipsets.

With the proper software (hint, hint!) you can get fancy
triggering, including negative trigger delay, hysteresis,
hold-off, etc. You can get real-time FFT spectrum analysis
(with optional peak tracking), and color spectrograms.

Synchronous waveform averaging allows stupendous noise
reduction... you can easily extract signals that were
totally buried in noise. See for example:
<http://www.daqarta.com/dw_wavg.htm>

Best of all, you get a signal generator that can create
almost any signal you want, with modulation including AM,
FM, PM, Burst, and Sweep on up to 4 independent streams per
stereo output channel. It can drive all your tests, and
provide the sync for the averaging as well. See:
<http://www.daqarta.com/dw_gen,htm>

(Actually, the generator is free. Even if you stick with
only an analog scope, or a cheap DSO, you will find plenty
of uses for the signal generator.)

Lots of other features, like a frequency counter that can
read low frequencies quickly with high precision (due to
reciprocal period methods). True RMS measurements. Sound
level (SPL) meter (if you have a calibrated microphone).
Histograms, including post-stimulus time histograms.

The $99 Pro version allows you to write macros to run
automated test sequences, allows custom spectrum response
limits for pass/fail production testing, and supports remote
control from custom software.

Best regards,


Bob Masta

DAQARTA v6.02
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, FREE Signal Generator
Pitch Track, Pitch-to-MIDI
Science with your sound card!

 

[Fred Abse]

I have an old Tek AM502 diffamp I use to front-end a digital scope. It
has switchable hi/lo cutoff frequency, lots of offset range, and tons
of CMRR. Gain goes up to 100K.

I have one of these. Only problem is the 1MHz B/W. Has been useful.though.

 

[Fred Abse]

I'd never go back to an analog scope or a VTVM.

I know it isn't tubes, but whaddabout your 610C?

 

[Jamie]

My Model 410 micro-microammeter uses an electrometer tube. It's fun to
use, but you have to wait for an hour for it to warm up. (It was $6
plus $25 shipping, and it works perfectly, if your idea of perfect
coincides with the peculiarities of a 1965 electrometer.)

Cheers

Phil Hobbs

I still have 2 HP RF volt meters I use, good for 1 ghz that are tubes
and has a chopper motor in the back

Jamie

 

[Fred Bartoli]

George Herold a écrit :

Hmm, All the same gain X BW product. I can only do 10**10 an order of
magnitude behind what TEK did ,(about?) 40 years ago?
Does anyone do better than 10**11? (all in one small box.)
Is there some fundamental 'thing' that sets a limit? (RC?)

George H.

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...

 

[Fred Abse]

I used an old HP RF voltmeter in gradual school.

Schooling should be a gradual process ;-)

I still use an HP vector voltmeter.

 

[Fred Abse]

It does have a needle, so I have to think a little.

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

There's a main
range switch and the "x" multiplier above it. Blast from the past.

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

ftp://jjlarkin.lmi.net/Keithley_1gig.JPG

But it measures 1e-14 amps, so I put up with it.

I intend to keep putting up with mine.

 

[Fred Abse]

I really like meters with needles.

You, me, both.

 

[Les Cargill]

Schooling should be a gradual process ;-)

http://www.imdb.com/title/tt0084917/quotes

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]

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

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

George H.

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.

 

[[email protected]]

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

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. ;-)

 

[Fred Abse]

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

But how often is that necessary?

I seldom need more than 3