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Author Topic: rigol-DS1054Z--Vertical distortion problem  (Read 2942 times)

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Offline biank88

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rigol-DS1054Z--Vertical distortion problem
« on: January 18, 2017, 10:40:57 PM »
Hi there folks, its a pleasure to join this community!
I've just received my new Rigol 1054Z oscilloscope and I've noticed something that I've never considered before.
In particular, If I hook up CH1 (1X, 1V/div) to the test signal (3Vpp, 1Khz) I get the following trace:

Now, if I change the vertical resolution to 200mv/div I get heavly distorted signals like:


Can this be considered "normal" behaviour for the frontend amplifiers?
Thanks for your attention!
« Last Edit: January 18, 2017, 10:45:13 PM by biank88 »
 

Online nctnico

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Re: rigol-DS1054Z--Vertical distortion problem
« Reply #1 on: January 18, 2017, 10:43:31 PM »
This is normal and every oscilloscope has this 'problem'. The phenomenon is called amplifier overdrive recovery. Once a transistor is saturated (overdriven) it takes a while to exit this state.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 
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Online borjam

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Re: rigol-DS1054Z--Vertical distortion problem
« Reply #2 on: January 18, 2017, 10:48:35 PM »
Yes, it's normal. When using a digital oscilloscope it's tempting to think that one can use the vertical controls to "zoom in" into a signal. Alas, it is possible only to a certain limited extent. You are not "zooming" but actually amplifying and adding some DC offset to the input signal fed to the A/D converter, which can indeed add distortion.

Anyone who hasn't made this mistake at least once, raise your hand! (I keep mine lowered)  :popcorn:
 
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Offline biank88

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Re: rigol-DS1054Z--Vertical distortion problem
« Reply #3 on: January 18, 2017, 10:51:33 PM »
Thanks for the quick reply.
I've studied the overdrive recovery for opamps but I've never seen any scope review giving any details about this effect.
 

Online borjam

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Re: rigol-DS1054Z--Vertical distortion problem
« Reply #4 on: January 18, 2017, 11:02:02 PM »
Thanks for the quick reply.
I've studied the overdrive recovery for opamps but I've never seen any scope review giving any details about this effect.
A link to this document was posted on another similar thread some time ago.

http://cp.literature.agilent.com/litweb/pdf/5989-0068EN.pdf

 

Offline hgjdwx

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Re: rigol-DS1054Z--Vertical distortion problem
« Reply #5 on: January 19, 2017, 02:03:57 AM »



« Last Edit: January 20, 2017, 01:49:17 AM by hgjdwx »
 

Online tautech

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Re: rigol-DS1054Z--Vertical distortion problem
« Reply #6 on: January 19, 2017, 07:37:39 AM »
Avid Rabid Hobbyist & NZ Siglent Distributor
 

Offline hgjdwx

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Re: rigol-DS1054Z--Vertical distortion problem
« Reply #7 on: January 19, 2017, 01:19:09 PM »



« Last Edit: January 19, 2017, 01:58:19 PM by hgjdwx »
 

Offline alsetalokin4017

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Re: rigol-DS1054Z--Vertical distortion problem
« Reply #8 on: January 19, 2017, 02:09:42 PM »
Hmmm.... I could swear that I've already seen those screenshots somewhere...    :horse:
The easiest person to fool is yourself. -- Richard Feynman
 

Offline 2N3055

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Re: rigol-DS1054Z--Vertical distortion problem
« Reply #9 on: January 19, 2017, 09:03:02 PM »
Rigol DS 1000Z series:

Offset Range (Probe ratio is 1X)

1 mV/div to 499 mV/div: ±2 V
500 mV/div to 10 V/div: ±100 V

 

Offline JPortici

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Re: rigol-DS1054Z--Vertical distortion problem
« Reply #10 on: January 19, 2017, 09:41:30 PM »
is that guy spamming those screenshots or what?
 

Offline Fungus

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Re: rigol-DS1054Z--Vertical distortion problem
« Reply #11 on: January 19, 2017, 11:36:13 PM »
Looks like everybody's posting in two threads.

 

Online nctnico

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Re: rigol-DS1054Z--Vertical distortion problem
« Reply #12 on: January 19, 2017, 11:48:58 PM »
is that guy spamming those screenshots or what?
He probably is but it does make me wonder whether Micsig has really solved overdrive issues or that the poster cherry picked a range where the analog frontend has the largest dynamic range. Still it is pretty impressive and usefull.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Online rstofer

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Re: rigol-DS1054Z--Vertical distortion problem
« Reply #13 on: January 20, 2017, 05:15:12 AM »
But why use an x1 probe setting?  Not that it has anything to do with the original traces but still...
 

Online nctnico

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Re: rigol-DS1054Z--Vertical distortion problem
« Reply #14 on: January 20, 2017, 05:30:09 AM »
The signal is probably fed into the oscilloscope with a coax cable from a function generator but that doesn't really matter for what is shown on screen.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline hgjdwx

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Re: rigol-DS1054Z--Vertical distortion problem
« Reply #15 on: January 20, 2017, 01:55:51 PM »
Don't doubt my tests! I just want everyone to know the truth, am I wrong? Mikeselectricstuff can prove that he can do the same test. Sorry, my English is not good.


Using the ground spring (the native 2V self-tuning signal)

« Last Edit: January 20, 2017, 02:07:26 PM by hgjdwx »
 

Offline Fungus

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Re: rigol-DS1054Z--Vertical distortion problem
« Reply #16 on: January 20, 2017, 08:37:57 PM »
Don't doubt my tests! I just want everyone to know the truth, am I wrong?

What happens if you set the probe input to x10 mode (the usual setting)?
 

Offline hgjdwx

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Re: rigol-DS1054Z--Vertical distortion problem
« Reply #17 on: January 20, 2017, 09:23:13 PM »
Don't doubt my tests! I just want everyone to know the truth, am I wrong?

What happens if you set the probe input to x10 mode (the usual setting)?

I set the probe input and scope to x10 mode, Test the native 2V self-tuning signal

Using ground clamp


Using the ground spring
« Last Edit: January 20, 2017, 09:35:13 PM by hgjdwx »
 

Offline hgjdwx

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Re: rigol-DS1054Z--Vertical distortion problem
« Reply #18 on: January 21, 2017, 01:56:20 PM »
This is of practical value,
When calibration probe compensation,
This is just a simple example, you should be good at discovering

 

Offline David Hess

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Re: rigol-DS1054Z--Vertical distortion problem
« Reply #19 on: January 23, 2017, 05:24:56 AM »
This is normal and every oscilloscope has this 'problem'. The phenomenon is called amplifier overdrive recovery. Once a transistor is saturated (overdriven) it takes a while to exit this state.

Not every oscilloscope suffers from overdrive induced distortion; sampling oscilloscopes are immune to non-destructive overdrive making them useful even at low bandwidths where a normal oscilloscope would usually be preferred. (1) Some old analog and digital storage oscilloscopes include cascode circuits for wider operating range and/or clamp circuits which limit the effects of overdrive.

The cause it not always transistor saturation.  Low leakage diodes used as clamps usually have slow reverse recovery time.  Amplifier stages which rely on balanced operation can suffer from thermal imbalance.

(1) This might explain why some Tektronix sampling instruments support real time operation with both sampling and real time timebases.

Yes, it's normal. When using a digital oscilloscope it's tempting to think that one can use the vertical controls to "zoom in" into a signal. Alas, it is possible only to a certain limited extent. You are not "zooming" but actually amplifying and adding some DC offset to the input signal fed to the A/D converter, which can indeed add distortion.

Analog oscilloscopes almost always suffer from the same problem.

Jim Williams discussed the problem in detail and shows examples of how subtle the problem can be and how to detect it in appendix B of Linear Technology application note 120 starting on page 14.

Thanks for the quick reply.
I've studied the overdrive recovery for opamps but I've never seen any scope review giving any details about this effect.

It is one of the things reviewers and marketing tend to ignore.  In the later case because it would make their products look bad.
 


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