Siglent SDS2000X Plus

[Martin72]

Hi,

Before I gave them away, I let all doing a self-cal test.
The test-lab itself were running thier tests fter at least 30min warm-up.

Martin

[voltsandjolts]

Just one question: were these the Factory Calibration test results or the results after re-calibration?

I doubt the cal lab had a setup which could actually make any adjustments to the siglent.
So there were no before/after adjustment readings, as there was no adjustment.
As such, the readings were more a verification of the factory cal.

IIUC

[Johnny B Good]

 If this is the case, I'm very impressed by Siglent's attention to detail in regard of their factory calibration (and also rather reassured by these results - I'm the proud owner of an SDS2104X Plus, upgraded last year to the 2504 spec).

[tautech]

If this is the case, I'm very impressed by Siglent's attention to detail in regard of their factory calibration (and also rather reassured by these results - I'm the proud owner of an SDS2104X Plus, upgraded last year to the 2504 spec).

Don't overlook the datasheet spec gives us the best idea of accuracy performance and this is something that no manufacturer wishes to get tripped up on so factory cal/accuracy should always meet or better datasheet spec.

Good Cal labs can easily write performance verification scripts from just the datasheet accuracy spec and the PV check values/ranges listed in the Service manual and or local one did just that for PV of their SDS2000X Plus with which they later discovered a blown 50 Ohm input that none of their techs would own up to. 

Back a few pages I posted about this and included the PV report failure page.

[Martin72]

Good Cal labs can easily write performance verification scripts from just the datasheet accuracy spec

They did when I see it right in the "full" cal-report.
All in all there were very good results, in the next days I´ll compare them to the report of a lecroy.
Only "worse" thing:
Firmwareupdates are only possible, when scopes are close to the next calibration.

[tautech]

Good Cal labs can easily write performance verification scripts from just the datasheet accuracy spec

They did when I see it right in the "full" cal-report.
All in all there were very good results, in the next days I´ll compare them to the report of a lecroy.
Only "worse" thing:
Firmware updates are only possible, when scopes are close to the next calibration.

Why, company policy ?

You need do some tests to prove this could be wrong.

[Martin72]

Hi Rob,

When doing a firmware upgrade siglent recommend to do the self calibration after this - I think for good reasons.
The official calibration based on the condition the scope got while the calibration process - when upgrading the firmware, scope doesen´t got the same condition as before - calibration is void.
When we give them away for new calibration, we can´t use them in a test setup, so we can also do a firmware upgrade because new calibration follows "immediately".

[tautech]

Hi Rob,

When doing a firmware upgrade siglent recommend to do the self calibration after this - I think for good reasons.
The official calibration based on the condition the scope got while the calibration process - when upgrading the firmware, scope doesen´t got the same condition as before - calibration is void.
When we give them away for new calibration, we can´t use them in a test setup, so we can also do a firmware upgrade because new calibration follows "immediately".

IMO such a belief regarding FW updates sucks, sorry but can't put this any kinder.

Think about this.....Siglent issue a 1 year factory Cal sheet with 6 months grace in case it sits in the suppliers store before sale and in that 6 months it is quite possible new firmware could be released which in our case would be installed before dispatch.
Why would Siglent release new firmware if there was any risk at all the instrument might no longer reach Cal (datasheet spec) ?

Also consider this....for an instrument with auto-cal ....and most modern stuff has this which can run at any time but primarily required in the warm up period but can run at anytime !
And that might ruin an official Cal....nope, not seeing or believing such arse covering BS !

[Martin72]

Why would Siglent release new firmware if there was any risk at all the instrument might no longer reach Cal (datasheet spec) ?

Therefore their note to calibrate it new after firmware update.
It might be BS in your eyes but that´s how it goes when you´re into quality processes like ISO9000 or Aviation/Mil.
On the other hand:
Siglent has reached the Pros with their "cheap" stuff...

[bdunham7]

When doing a firmware upgrade siglent recommend to do the self calibration after this - I think for good reasons.
The official calibration based on the condition the scope got while the calibration process - when upgrading the firmware, scope doesen´t got the same condition as before - calibration is void.
When we give them away for new calibration, we can´t use them in a test setup, so we can also do a firmware upgrade because new calibration follows "immediately".

So are you permitted to run the self-calibration procedure on a regular basis?

[Martin72]

More or less - When it´s on it´s way to got a new calibration, so why not doing an upgrade and self-cal immediatley before it goes away.
This is the "brainfuck" in Quality Processes:
When the scope is external calibrated (and reported), we can do (official)measures with it because it´s proofed that this one meets it´s own specs.
We got the report and could handle it out to customer/auditor when he wants to see it.
It´s valid for one year - based on the condition the scope got when it was calibrated.

[oz2cpu]

SDS scope question ??

what kind of funny clock skew or free running issue are we seeing here ??
why is this not stable ?
is it the scope ? or the generator ? that is causing this ?

https://youtu.be/AQZ0Y1W4-ZI

[bdunham7]

More or less - When it´s on it´s way to got a new calibration, so why not doing an upgrade and self-cal immediatley before it goes away.

I don't know if you are replying to me or tautech.  What I mean is can you run a self-cal on a daily basis and so on?  Or is that somehow prohibited?

[bdunham7]

SDS scope question ??

what kind of funny clock skew or free running issue are we seeing here ??
why is this not stable ?
is it the scope ? or the generator ? that is causing this ?

https://youtu.be/AQZ0Y1W4-ZI

That is really a non-issue and is a result of the limitations of the sinx/x interpolation with not very many samples.  As the actual point of the samples varies in the capture, the sinx/x interpolation comes out a bit different on different traces.  Usually this shows up as a widened, jumpy trace, but if the sample rate is almost an exact multiple of the signal frequency, the dots can 'crawl' instead of moving around quickly so you see the squirming effect.  If you have the same equipment, you can do a series of single captures and switch back and forth between dots and vectors (sinx/x) and you'll see what I mean.

[tautech]

SDS scope question ??

what kind of funny clock skew or free running issue are we seeing here ??
why is this not stable ?
is it the scope ? or the generator ? that is causing this ?

https://youtu.be/AQZ0Y1W4-ZI

That is really a non-issue and is a result of the limitations of the sinx/x interpolation with not very many samples.  As the actual point of the samples varies in the capture, the sinx/x interpolation comes out a bit different on different traces.  Usually this shows up as a widened, jumpy trace, but if the sample rate is almost an exact multiple of the signal frequency, the dots can 'crawl' instead of moving around quickly so you see the squirming effect.  If you have the same equipment, you can do a series of single captures and switch back and forth between dots and vectors (sinx/x) and you'll see what I mean.

Yes, should also check what max mem depth has been set.

[Martin72]

@bdunham7
To you.
And no, this we couldn´t for the reasons explained before*.
Apart from this and general, why making daily self-cals...

*) When we could make sure, that self-cal wouldn´t affect the measured values on calibration, then this shoudln´t be a problem then.
But: When it wouldn´t make any affections, why can you make self-cals...

[2N3055]

SDS scope question ??

what kind of funny clock skew or free running issue are we seeing here ??
why is this not stable ?
is it the scope ? or the generator ? that is causing this ?

https://youtu.be/AQZ0Y1W4-ZI

You can try scope in dot mode... Dot mode emulates repetitive sampling of a sort..

If it is smeared, that is probably AWG... set rise/fall time to 1.7ns or more and see.

[bdunham7]

@bdunham7
But: When it wouldn´t make any affections, why can you make self-cals...

I don't have time for a long reply, but the short answer is that when your lab does a calibration, they are essentially verifying that the self-calibration process itself is working accurately.  There's not much assurance that the scope would stay accurate for a year without self-cal.  Unfortunately Siglent's manuals don't go into this as extensively as Tek does with their Signal Path Compensation, but not being allowed to do the self-cal between calibrations would be like insisting that you turn off autozero and not use ACAL on your 3458A. 

Some Siglents have a 'Quick-Cal' feature that runs in the background but I don't see it on the SDS2000X+.  Perhaps it is just there and there's no menu option to defeat it. 

Anyway, unless you document and build your own calibration history, you have to combine the cal report with the manufacturers specifications and instructions.  And Siglent doesn't tell you not to run self-cal, just the opposite.  IMO.  Best of luck convincing anyone else.

[Martin72]

I think, there is a translation problem.

[bdunham7]

I think, there is a translation problem.

I'm not sure where?

[tautech]

I think, there is a translation problem.

I'm not sure where?

Between last and this century ! 

Indeed it does seem Cal labs record FW versions and have for some years as some old equipment was notorious for crashing and/or losing calibration settings ! 

But hell, what equipment does that these days but the industry is so stuck in its ways they cannot identify those brands and models and instead places all equipment in the same boat, maybe in an attempt to CYA.

Marty mentions ISO9000, well maybe it's time that got tipped upside down and given a good shake until the BS falls out.

[bdunham7]

Indeed it does seem Cal labs record FW versions and have for some years as some old equipment was notorious for crashing and/or losing calibration settings ! 
Marty mentions ISO9000, well maybe it's time that got tipped upside down and given a good shake until the BS falls out.

A company policy requiring a cal check after firmware update might just be 'abundance of caution' (barf) but not using self-cal because it changes the measurements is just not right, IMO.  If I'm understanding his company policy correctly.

I don't know the ins and outs of ISO9000, but this can't possibly be a correct interpretation because getting calibration certificates on scopes has been done for a long, long time.  So if you get your all analog scope calibrated, do they tape/seal  the vertical position knobs in place?  No, the calibration and specifications assume you will zero it as needed before measurement.  What I was pointing out that doing a calibration verification right after the proper warmup and self-cal precisely proves the scope is in spec--right after the self-cal.  So the 'condition' of the scope could be said to include "within XX hours and X degrees C of self-cal", just like a DMM might specify a time and temperature delta since ACAL and/or zero/autozero.  Unfortunately, as I've read some more in the manuals, Siglent doesn't really elaborate all that much, just telling you to run self-cal if the temperature changes 5C.  But from experience I know that the zero point can drift around a bit on the lower ranges and an hour warmup plus a self-cal puts it right.

[Performa01]

My two cents with regard to the calibration:

• An SDS2000X Plus (or any other) DSO will certainly meet its specifications in a lab environment within the usual temerature window of 23 °C +/- 5 °C even without self-calibration.
• The official calibration in a cal-lab will tell you the results at a certain constant temperature, traditionally 23 °C, nowadays also 20 °C.
• If the official calibration has been preceeded by a self-cal at this exact temperature, the results will be particularly good. They will show you the qualities of the internal references of the instrument.
• You'll be able to get similarily good results at different temperatures anytime if you run self-cal again.
• If you never run self-cal in the actual working environment, you will not get the accuracy as documented by the official calibration, but you will certainly still stay within spec as long as the environmental conditions aren't abysmal, i.e. normal lab conditions.

But I know, the official regulations have more to do with following strict rules instead of common sense...

[tautech]

My two cents with regard to the calibration:

• An SDS2000X Plus (or any other) DSO will certainly meet its specifications in a lab environment within the usual temerature window of 23 °C +/- 5 °C even without self-calibration.
• The official calibration in a cal-lab will tell you the results at a certain constant temperature, traditionally 23 °C, nowadays also 20 °C.
• If the official calibration has been preceeded by a self-cal at this exact temperature, the results will be particularly good. They will show you the qualities of the internal references of the instrument.
• You'll be able to get similarily good results at different temperatures anytime if you run self-cal again.
• If you never run self-cal in the actual working environment, you will not get the accuracy as documented by the official calibration, but you will vertainly still stay within spec as long as the environmental conditions aren't abysmal, i.e. normal lab conditions.

But I know, the official regulations have more to do with following strict rules instead of common sense...

Yes, all common sense that seems to be not that common. 
Made a post on the Siglent forum about this that I believe could do with some discussion.

[bdunham7]

• An SDS2000X Plus (or any other) DSO will certainly meet its specifications in a lab environment within the usual temerature window of 23 °C +/- 5 °C even without self-calibration.

...

• If you never run self-cal in the actual working environment, you will not get the accuracy as documented by the official calibration, but you will vertainly still stay within spec as long as the environmental conditions aren't abysmal, i.e. normal lab conditions.

I agree with everything you said except I'd regard these two statements as very likely true, but not proven, especially over the course of a year with a sample size large enough to give you an appropriate confidence interval.  I suspect that they mostly are true in general simply because the actual tolerances of most DSOs are wide enough to drive a truck through.  But if guaranteed performance is what you are after, it makes no sense to not use self-cal, since one of the conditions of the calibration certificate was 'recent self-cal'. 

Siglent doesn't get into these details explicitly enough in their manual.  Tek does, they state "thou shalt run SPC", as in this excerpt from a TDS6000B manual:

To meet specifications, the following conditions must be met:
 The oscilloscope must have been calibrated in an ambient temperature
between 20 °C and 30 °C (68 °F and 86 °F).
 The oscilloscope must be operating within the environmental limits listed in
Table 1--11, page 1--17.
 The oscilloscope must be powered from a source that meets the specifications listed in Table 1--9, page 1--15.
 The oscilloscope must have been operating continuously for at least 20
minutes within the specified operating temperature range.
You must perform the Signal Path Compensation procedure after the
20-minute warm-up period, and the ambient temperature must not change
more than 5 °C (9 °F) without first repeating the procedure. See page 3--2 for
instructions to perform this procedure