Hi and thanks for the advice.
actually the solution of a signal amp sounded me ok.
But i trust your advice completely. I will look at something else ...
If you can find a Tektronix 7000 series mainframe with 7A22 amplifier plugin you would have one of the best low noise scopes systems ever made.
Tektronix 7A22 Differential Amplifier Plug-In | eBay
If you keep your eye on Ebay you will find decent 7K mainframes for sale in Europe - or Ship from the US
well i like very much this solution of plug-in ...
actually i do not understand why is not more popular.
Like a unit with more slot to fill with the modules needed.
Very very smart. I will think about that.
Next move must be a smart one. No toys anymore.
I am a grown-up child now ...
Thanks a lot again
regards, gino
P.S. i am trying hard to get to UK ... the offer there is huge compared to where i presently live.
I purchased one of these; UNI-T UTD2052CL 50MHz 500Ms/s Digital Storage Oscilloscope Dual Channels 7" LCD | eBay
I had it callibrated before supply and it works as well as my Hameg HM604 that I needed to replace due to the physical size!
I had it callibrated before supply and it works as well as my Hameg HM604 that I needed to replace due to the physical size!
No I meant a stand alone FFT analyser like the Standford research SR760 or SR770 second hand at an affordable price.
I'm not sure why they even bother putting the FFT feature on scopes they are so limited in Dynamic range and FFT points they are useless for serious work.
A PC sound card and FFT software would be a great way to start with limited funds if one was careful with the input signal levels.
I've not sat down and really thought about it too much, but "off the cuff" how much dynamic range is available without AC coupling when you have say a 50V DC input and you want to look at 1mV noise ripple levels? I suspect the cheaper digital scopes have 8 Bit ADC's.....
OH agreed - well said, but I understand this is how the cheaper digital scopes "AC couple"!!!! How much do Relays + a Cap cost?
That said, I've just looked at my Agilent infiniium 54835A (2.5GHz, 20GSa/s) and its Max input is rated at 5Vrms 50 ohms.... (I use x10 active probes so this has never been an issue).
Yep, it's an 8 bit ADC. It says so in the manual, "vertical resolution 8 bits". The ADC carries a custom Rigol number but has been reverse engineered to be a Hittite HMCAD1511.
A while ago I posted the results of the scope's own noise in this thread (coupled to GND, 1 mV and 1 us/div, BW limited to 20 MHz, repeated at 10 V/div).
That did not look too good in the 1 mV/div setting, and I just realised that after hacking the scope to a higher specced model, I had not redone the self cal. I figured the factory calibration parameters would not be overwritten, but now I'm not so sure... Later I had it do a self cal and maybe that's why it now looks better?? Not sure, though.
For comparison I repeated the tests, but now one at 1 ms/div too. Not bad for such a cheap scope.
Attachments
Just to restate, I'm not sure if the Rigol has "real" AC coupling or just Digital HPF.
With HPF the issue will be small signal onscreen dynamic range in the presences of a larger DC input level (the ADC will be maxed out by the DC offset, 8Bits is really not much resolution when expended over the full screen, forget about once its "used up" by a large DC offset.
With HPF the issue will be small signal onscreen dynamic range in the presences of a larger DC input level (the ADC will be maxed out by the DC offset, 8Bits is really not much resolution when expended over the full screen, forget about once its "used up" by a large DC offset.
Here's the reverse engineered schematic of the DS1054Z's front end. Note (bottom left) the 220 nF cap in series with 220 Ω resistor bypassed by a relay. Here the selection is made between DC (relay closed) or AC (relay open, as in the drawing) coupling. I.e. "real" AC-coupling in the analogue domain, no digital gimmicks.
Edit: the Agilent you refer to has that low max input voltage only in the 50 Ω input impedance setting. In the 1 MΩ setting it's a lot more. See page 12 of this sheet.
Oh, crossed posts
Yep, then that's confirmed the Rigel has true AC coupled input mode
Good to see they have not gone "So Cheap"
Sorry, my bad, the Agilents I have are the infiniiums 54853A (not 84835A) they are only 50 Ohms input...
To be honest I very rarely use them I think I've powered them once this year, I just default to using the Tek 11302A Analogue scopes.
I used to use the Digital scopes with HUD glasses via there VGA output, so I could adjust PCB's without lifting my head to view the scope screen and the ever present danger of slipping the scope probe and damaging the board.
The HUD Glasses work well and it means I don't need the scope in my line of sight, my lab bench is already very crowded.
Yes this "by quote only" it is a fact, but this is happening every time to all GW Instek distribution chain when there is a new addition.
I will predict that end of June complete pricing info all over the world will clear up.
AND at the speed limit one is driving at it doesn't take long to warp the
bearing seals. -- Don't as me how I know.
When benchmarking analog VS "Digital" LPF, the second has higher accuracy at filtering.
And the benefits come due the fact that is adjustable.
"Digital" LPF does not translate to gimmick software tricks, it is an filter controlled by software and not by a regular knob.
HIOKI Japan using digital LPF in some of their latest multimeter, so their filter to be adjustable according to variable frequency drive inverters (primary frequency), this can be at 100Hz or 200Hz or 400Hz.
Yep, you get 30 mins. After that, if you very badly need a post edited or removed, a moderator will have to do it for you.
I know other forums where a perpetual edit is normal, on this forum it's only allowed for the first post of a thread.
I know other forums where a perpetual edit is normal, on this forum it's only allowed for the first post of a thread.
I think that you are a bit confused, regarding proper setup of an Oscilloscope so this to measure ripple.
Highest importance is an Oscilloscope to be sensitive by design, and able to measure down to 1mV.
By activating Bandwidth limit to 20MHz, the Oscilloscope becomes able to measure low volts by even using auto-set button.
The use of additional active filter in one modern digital Oscilloscope this is possible if you do buy an Oscilloscope with such add-on capability.
It might worth for you, just to increase your education, to download and read GW Instek GDS-2000A user guide.
In such documents there is even application examples which are extremely valuable as theory coming from engineers with fresh training.
Sorry, but your missing the point!
As my Mother would say, Please don't try teaching your Grandmother how to suck eggs...
We are discussing measuring a very low amplitude signal (PSU Noise) riding upon a higher voltage "DC" rail.
LPF will attenuate the signal component above the filters corner Frequency - the OP however has requested a method to look at a noise "ripple" riding his PSU "DC" rails - for which he needs a HPF (AC coupling).
Please don't try and promote GW Instek to me, its cheap test equipment I have Zero interest in - I occasionally encounter Instek scopes on production lines in China and despise using them for anything but the most basic measurements - Signal or no signal etc...
I can assure you I know how to use both analogue and Digital oscilloscopes, and in fact the later Analogue oscilloscopes also feature "Autoset".
On my analogue scopes I can enable the Autoset by simply pressing the button on the scope probe, although I've disabled the option because I find it annoying (I keep accidentally pressing the button and loose the current scope settings).
While its possible to use a scope to look at noise, it tells you little about the noise spectrum, an FFT analyses is a far more effective tool for this application. I'm talking about a dedicated FFT analyses with wide Dynamic range, not the Micky Mouse FFT mode they offer on Digital scopes.
As my Mother would say, Please don't try teaching your Grandmother how to suck eggs...
We are discussing measuring a very low amplitude signal (PSU Noise) riding upon a higher voltage "DC" rail.
LPF will attenuate the signal component above the filters corner Frequency - the OP however has requested a method to look at a noise "ripple" riding his PSU "DC" rails - for which he needs a HPF (AC coupling).
Please don't try and promote GW Instek to me, its cheap test equipment I have Zero interest in - I occasionally encounter Instek scopes on production lines in China and despise using them for anything but the most basic measurements - Signal or no signal etc...
I can assure you I know how to use both analogue and Digital oscilloscopes, and in fact the later Analogue oscilloscopes also feature "Autoset".
On my analogue scopes I can enable the Autoset by simply pressing the button on the scope probe, although I've disabled the option because I find it annoying (I keep accidentally pressing the button and loose the current scope settings).
While its possible to use a scope to look at noise, it tells you little about the noise spectrum, an FFT analyses is a far more effective tool for this application. I'm talking about a dedicated FFT analyses with wide Dynamic range, not the Micky Mouse FFT mode they offer on Digital scopes.
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