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Siglent SDS1104X-E Quick Cal Question

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TomKatt:
Long time EEVblog viewer, new poster so pls be kind ;-)

Recently procured a Siglent SDS1104X-E to supplement my old reliable HP 180A CRO and couldn't help myself in immediately upgrading it to 200 MHz BW with all the other goodies (which was so simple to do one wonders if this isn't almost expected by Siglent?).  While compensating the probes I observed what I believe is some kind of calibration anomaly - Auto Set shows the Siglent calibration square wave as dead-on 1 KHz, but the P-P voltage is calculated as 3.10 volts and the channel data on the right of the screen also indicated a -1.48V offset...  Looking through the documentation I can find no spec listed for the calibration waveform, but I would 'assume' it should be 3.00 volts even.  Performing a Self Cal after the unit is warmed up does not change anything.  I also see that even in the user manual the calibration wave illustration shows a CH1 DC offset of -1.46 volts where I would expect an even 1.50 for the 3V square wave, so it seems that the manual example is likewise off from the expected 3V measurement.

Anyway...  that aside my actual question is what does the Quick Cal setting do?  The manual doesn't mention how that works or what it does, and as an ON/OFF setting rather than a 'RUN' type argument it seems to infer some ongoing operation...   I searched the forums here but likewise did not find anything that describes how the Quick Cal setting works.  Would someone be kind enough to describe the Quick-Cal setting and the best use of it vs Self Cal?

Thanks in advance!

edit - should have mentioned that my 3.10V measurement was after setting probe compensation at 10X to a proper, sharp square wave, so I do not believe the 3.10V measurement was a result of probe overshoot.

bdunham7:
Quick Cal is in your manual on p. 181.  If the setting is enabled, it will perform an abbreviated Self Cal whenever the temperature changes by more than a few degrees to minimize offset drift in a non-temp-controlled environment.  It might do the procedure during instrument warmup as well, I'm not sure.  Neither quick or self calibration procedures have anything to so with the probe calibrator output and there's no expectation that you would see exactly 3 volts or 1.5 volts offset as vertical accuracy has nothing to do with probe compensation.

TomKatt:
Thanks for the reply!

So, does that mean the scope has a built in thermal sensor that monitors the environmental temperature?  And wouldn't periodic calibration routines interfere with live measurements?  Strange feature.

I understand the calibration process would not directly affect the probe calibration signal, but it would affect the resulting measurement display if it was off.  My old CRO has two calibration voltage levels that are dead on - I guess I expected similar operation on the new fangled equipment.

Fungus:

--- Quote from: TomKatt on June 27, 2022, 12:35:47 pm ---(which was so simple to do one wonders if this isn't almost expected by Siglent?).

--- End quote ---

Of course it is. Everybody would buy Rigols if they didn't allow it.


--- Quote from: TomKatt on June 27, 2022, 12:35:47 pm ---Looking through the documentation I can find no spec listed for the calibration waveform, but I would 'assume' it should be 3.00 volts even.

--- End quote ---

I wouldn't assume anything.

It's probably based on 3.3V internally (they're not going to put in a special voltage regulator just for that signal). What does your HP say?

Fungus:

--- Quote from: TomKatt on June 27, 2022, 12:58:48 pm ---wouldn't periodic calibration routines interfere with live measurements?

--- End quote ---

Apparently it does:  :)

https://www.eevblog.com/forum/testgear/unlocking-siglent-sds1104x-e-step-by-step/msg3444072/#msg3444072

You don't have to turn it on though.

I wouldn't rely on an oscilloscope for voltage readings better than about 3-4% error. Look up the spec for vertical gain accuracy...

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