Products > Test Equipment
Siglent SDS1104X-E Quick Cal Question
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Performa01:
Yes, times have changed since the HP 180A.

The internal calibration source of a modern DSO like the Siglent SDS1000X-E is the reference for the offset DAC, which has far better resolution than just 8 bits.

The old (and partially outdated) review in this thread

https://www.eevblog.com/forum/testgear/siglent-sds1104x-e-in-depth-review/

demonstrates and discusses all the important basics of this remarkable little scope.

You can find a verification of the DC accuracy on page 51 of the document, which was better than 2% over the entire gain range (500 µV/div to 10 V/div) and better than 1% for 1 mV/div to 500 mV/div.

There's also a demonstration measuring 205 V DC to less than 0.08% error, making use of the very accurate channel offset.

Not everything what cannot exist in old obsolete CROs has to be a "weird feature".
In contrast to some much more expensive instruments, you can turn Quick Cal off in the SDS1000X-E - if you really think you cannot afford three seconds of interruption for an accurate offset during warmup. Once warmup is completed, you'll most likely never see this again, unless your room temperature changes by more than maybe 5 K.
TomKatt:
Your review was actually one of the primary influences in my purchase decision!  Thanks for that extremely in-depth work!
rf-loop:

--- Quote from: Performa01 on June 27, 2022, 03:21:15 pm ---...you can turn Quick Cal off in the SDS1000X-E - if you really think you cannot afford three seconds of interruption for an accurate offset during warmup. Once warmup is completed, you'll most likely never see this again, unless your room temperature changes by more than maybe 5 K.

--- End quote ---
I will add tiny bit more...

@TomKatt:
Example if want use slow roll mode inside first 30minute after power on, in some cases it is mandatory to turn Quick-Cal:OFF.
If Quick-Cal:ON it resets rolling every 15s if any active channel (1x) sensitivity is between 500uV - 2.0mV/div (of course same is 10x 5mV - 20mV/div.)
Same also if need do other long time acquisitions in this warming period or situations where temp change may trig Quick-Cal process. For avoid these acq.resets just Quick-Cal:OFF.
Fortunately and wisely, this has been done so that it can be shut down when need.


Cal Out: Only designed purpose for front panel Cal out is for adjust probe "LF compensation"  (adjusting square top/bottom as straight as possible. It is not designed for level cal or time cal etc as can be or is in some old timers.)  Also it is not at all suitable source for internal adjustments in every channel front end, it need external generator)

TomKatt:
Just a quick follow up - I tested the calibration signal terminals with my Greenlee 820A (aka Brymen 827s) True RMS meter, which showed a voltage of 1.498 with a duty cycle 0f 50.02%.  That works out to 2.996V P-P.  My HP 180A CRO shows the Siglent calibration signal as pretty close to 3V even, perhaps just shy of the center of the division line (analog scopes rely on a bit of tongue at the right angle) , which seems to agree with the meter reading (and always has in the past).  I note the Siglent measurement occasionally flips back and forth between 3.10 and 3.08 (but never 3.09?)...

In fairness, none of my equipment is officially calibrated (other than the Siglent being new with factory Cal certificate), and my HP 180A is 55 years old (and still running like a champ - they don't make gear like that anymore :P).  Also, the Siglent measurement of 3.10V is pretty much within it's advertised spec of +/- 3.0% if I average the 3.08 - 3.10 readings to 3.09V.  I also 'upgraded' the scope to 200 MHz BW (status now displays model as SDS1204X-E), which although I do not believe affects the internal calibration, I have no real idea what ramifications that modification may have.

Again, I understand that vertical accuracy is not necessarily the primary purpose of a scope as a tool, but I guess I expected "perfection" from a virtually brand new device pretty much out of the box, especially at lower voltage and frequency.  But, having fired up my old CRO for comparison purposes, I was instantly reminded how advanced technology has become  8)  I'd be hard pressed to measure the multitude of parameters the Siglent offers with a simple button press on an old CRO.

Thanks again for all of the informative comments - I will say that Siglent's description of the Quick-Cal feature leaves much to be desired.
bdunham7:

--- Quote from: TomKatt on June 28, 2022, 10:49:33 am --- Also, the Siglent measurement of 3.10V is pretty much within it's advertised spec of +/- 3.0% if I average the 3.08 - 3.10 readings to 3.09V.  I also 'upgraded' the scope to 200 MHz BW (status now displays model as SDS1204X-E), which although I do not believe affects the internal calibration, I have no real idea what ramifications that modification may have.

Again, I understand that vertical accuracy is not necessarily the primary purpose of a scope as a tool, but I guess I expected "perfection" from a virtually brand new device pretty much out of the box, especially at lower voltage and frequency. 

--- End quote ---

Well first, you have to read all the specs for DC gain, not just the headline 3% figure.  However, what you are seeing is something else and interpreting your scope measurements takes some thinking.  Possible causes for unexpectedly high errors here include not using enough of the ADC range and not accounting for noise.

Try this: Just to be sure all the settings are correct, start by pressing the 'Default' button and then setting up the scope from there. Using one of the probes that came with the scope, set to 1X, connect CH1 to the calibrator output and set the scope for 500µs/div, 500mV/div and a CH1 offset (position) of -1.500V.  Perhaps that is what you are already doing.    Now select four measurements, Pk-Pk, Amplitude, StDev and RMS.  Note all four measurements, then from the CH1 menu, press the button under 'BW Full' so that it reads 'BW 20M'.  Note any changes.


--- Quote ---I will say that Siglent's description of the Quick-Cal feature leaves much to be desired.

--- End quote ---

The days of detailed manuals hundreds of pages long explaining every technical detail of a complete schematic and parts list is loooooong gone!  But yeah, they could have written two paragraphs.
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