Bandwidth limit on Siglent SDS2000X Plus oscilloscope

[swmcl]

Hi,

I recently purchased an SDS2104X Plus oscilloscope.  With the deal was an offer to upgrade from 100MHz to 200MHz.  I have followed some instructions given by the seller but my screens did not behave like they said in the instructions.

How do I check what the B/W limit is in my scope ??

Rgds,

Steve

[KeBeNe]

please read this page -> https://www.eevblog.com/forum/testgear/siglent-sds2000x-plus-hack/400/

[tautech]

Hi,

I recently purchased an SDS2104X Plus oscilloscope.  With the deal was an offer to upgrade from 100MHz to 200MHz.  I have followed some instructions given by the seller but my screens did not behave like they said in the instructions.

How do I check what the B/W limit is in my scope ??

Rgds,

Steve

The free BW upgrade if applied correctly will change the model # to SDS2204X Plus.
The scope should identify itself as that model which you can confirm in SYS Info.

What did the seller provide ?
The scope only or the scope and BW upgrade license ?

If the upgrade license was supplied it probably needs be redeemed at the Siglent licensing website by inserting the Authorized code, the model series, SN# and selecting the 100-200 BW upgrade license.

This will generate the official license that you can download the PDF licensing instructions which has the license in it or download the USB licensing .LIC file that you transfer onto the root folder of a USB stick and point the scope to it for automatic licensing install.

Most I have done is IIRC 8 licenses this way and they install in just a second or 2 each < no typing or error risks and so simple.

[swmcl]

Thanks Tautech,

I purchased the scope from AppVision in Sydney.  So that is a scope and other bits and pieces (bag and probes) in one purchase.  I have no issue with their help so far except that they do take a little bit of time to respond.

I went to a website and followed some instructions but the on-screen results on the scope were a little different to what the website stated.

It sounds as though we are talking the same thing.  I wondered if there was a menu option that showed where the software-limited B/W was sitting.

Rgds,
Steve

[Mouse69]

Hi Steve,

Page 320 of the user manual: Operate Utility>System Setting>System Status to check the system status.

You get a list of HW, serial No etc. including the model number (right at the bottom) which should have changed to: SDS2204X Plus

[swmcl]

Thanks Mouse69,

My scope does not have this sequence of options: Utility > System Setting > System Status

It does however have: Utility > System Info

In System Info it now shows a model of  "SDS2204X Plus"

So the upgrade from a SDS2104X Plus is complete it seems.

Thanks all.

[Martin72]

The "real" bandwith of a 2104X+ is way over the 100Mhz, would be interesting to know what bandwith you have now with the 200Mhz upgrade.

[tautech]

The "real" bandwidth of a 2104X+ is way over the 100Mhz, would be interesting to know what bandwidth you have now with the 200Mhz upgrade.

Yes, this is something I need do for 'the record'.
Hopefully I can fit it in tomorrow after installing the free BW upgrade option.

For the record and as tested before, SDS2104X Plus -3dB BW is ~185 MHz. (checked with 3 different sinewave sources)

[TheDefpom]

According to my Bodnar pulser for rise time it is 560MHz, according to my testing of the vertical response for -3dB it is in excess of 600MHz, from memory about 670MHz. (after conversion up to 500MHz bandwidth obviously)

[tautech]

The "real" bandwidth of a 2104X+ is way over the 100Mhz, would be interesting to know what bandwidth you have now with the 200Mhz upgrade.

Yes, this is something I need do for 'the record'.
Hopefully I can fit it in tomorrow after installing the free BW upgrade option.

For the record and as tested before, SDS2104X Plus -3dB BW is ~185 MHz. (checked with 3 different sinewave sources)

For the record....
SDS2104X Plus with free BW upgrade promotional license applied to become SDS2204X Plus....

SSG3000X waveform first checked @ 100 MHz to be precisely 1V p-p.
-3dB BW is now 300 MHz + a couple of MHz, an increase of ~115 MHz over SDS2104X Plus

[pdenisowski]

How do I check what the B/W limit is in my scope ??

As @tautech posted above, the easiest way to check the bandwidth of your scope is to use a sinusoidal input signal of a known amplitude and increase the frequency until the measured amplitude has decreased by 3 dB.  That frequency is the "bandwidth" of your oscilloscope as defined by most scope manufacturers.

Bandwidth can also be specified in terms of the rise time of a pulse, but this is a more difficult measurement to make (need a good pulsed signal source) and also requires some knowledge of the frequency response (Gaussian vs. brick wall) of the scope's front end to get an accurate number.

I talk about both of these in my video on oscilloscope bandwidth:

[tautech]

The "real" bandwidth of a 2104X+ is way over the 100Mhz, would be interesting to know what bandwidth you have now with the 200Mhz upgrade.

Yes, this is something I need do for 'the record'.
Hopefully I can fit it in tomorrow after installing the free BW upgrade option.

For the record and as tested before, SDS2104X Plus -3dB BW is ~185 MHz. (checked with 3 different sinewave sources)

For the record....
SDS2104X Plus with free BW upgrade promotional license applied to become SDS2204X Plus....

SSG3000X waveform first checked @ 100 MHz to be precisely 1V p-p.
-3dB BW is now 300 MHz + a couple of MHz, an increase of ~115 MHz over SDS2104X Plus

And while I have a stock SDS2354X Plus unpacked......

Same setup for the source as above but this time pushed to 491 MHz for the -3dB point....

Result = purchase a 350 MHz model and receive nearly a 500 MHz one. 

[seronday]

Out of curiosity, what reference frequency did you use for the -3dB bandwidth calculation ?

[tautech]

Out of curiosity, what reference frequency did you use for the -3dB bandwidth calculation ?

No calculations are required when you have a 3.2 GHz RF gen. 

Only a check levels are correct at some base frequency before pushing upward, we used 100 MHz 1V p-p as mentioned here:
https://www.eevblog.com/forum/testgear/bandwidth-limit-on-siglent-sds2000x-plus-oscilloscope/msg4968844/#msg4968844

Otherwise if using the Bodnar pulser, it provides extremely fast edges @ 10 MHz

[Martin72]

Otherwise if using the Bodnar pulser, it provides extremely fast edges @ 10 MHz

Besides the approximate formula (0.35/risetime), you could also try this:

https://www.teledynelecroy.com/doc/frequency-response-measurements

This didn't really work for me when I had a SDS2000X+, but since then 2..3 firmware updates have passed.
Maybe it works now.

[TimFox]

One problem with using 0.35/T_rise is knowing in advance what the actual rise time of the pulse source is.
Approximately, the two rise times (pulse and scope) add in quadrature.

[TheDefpom]

The Leo Bodnar pulsar is sold as a 40ps unit, but comes with a cert showing what the supplied unit is actually doing, mine was ~35ps

[seronday]

Out of curiosity, what reference frequency did you use for the -3dB bandwidth calculation ?

No calculations are required when you have a 3.2 GHz RF gen. 

Only a check levels are correct at some base frequency before pushing upward, we used 100 MHz 1V p-p as mentioned here:
https://www.eevblog.com/forum/testgear/bandwidth-limit-on-siglent-sds2000x-plus-oscilloscope/msg4968844/#msg4968844

Otherwise if using the Bodnar pulser, it provides extremely fast edges @ 10 MHz

OK. Thanks Tautech.
I did not realize that Siglent had specified the BW performance verification test differently for the SDS2000X Plus.

In the service manual for the SDS2000X HD, section 5.4, Siglent specify using 1 Mhz as the frequency for the reference level when working out the bandwidth performance.

Regards.

[tautech]

Out of curiosity, what reference frequency did you use for the -3dB bandwidth calculation ?

No calculations are required when you have a 3.2 GHz RF gen. 

Only a check levels are correct at some base frequency before pushing upward, we used 100 MHz 1V p-p as mentioned here:
https://www.eevblog.com/forum/testgear/bandwidth-limit-on-siglent-sds2000x-plus-oscilloscope/msg4968844/#msg4968844

Otherwise if using the Bodnar pulser, it provides extremely fast edges @ 10 MHz

OK. Thanks Tautech.
I did not realize that Siglent had specified the BW performance verification test differently for the SDS2000X Plus.

In the service manual for the SDS2000X HD, section 5.4, Siglent specify using 1 Mhz as the frequency for the reference level when working out the bandwidth performance.

Regards.

Not exactly.

Tests are done starting at 1 MHz to beyond DSO rated BW.
Eg, for SDS2104X HD all the below frequencies are used and documented for verification checks = does it or not pass a Cal.
1M, 1.14M, 1.31M, 1.50M, 1.72M, 1.97M, 2.25M, 2.57M, 2.95M, 3.37M, 3.86M, 4.42M, 5.06M, 5.79M, 6.63M, 7.59M, 8.69M, 9.94M, 11.38M, 13.03M, 14.91M, 17.07M, 19.54M, 22.36M, 25.60M, 29.30M, 33.54M, 38.39M, 43.94M, 50.30M, 57.58M, 65.90M, 75.43M, 86.35M, 100.00M, 113.14M, 129.51M, 148.24M, 169.68M, 200.00M

This will be an automated test using the prescribed Fluke 9500B oscilloscope calibrator.

Few of us have such a beast therefore just finding the -3dB BW rolloff is quite sufficient for our needs.

Typical method is set source to 1V p-p and start winding up frequency until the scope displays 0.707V p-p from a 1V sinewave input. Just don't forget it need be done using a 50 Ohm system. 

[seronday]

The last paragraph on page 38 of the SDS2000X HD service manual describes the method of calculating the dB change in level at each of the measured frequencies, by using the level at 1 MHZ as the reference.

If using a much higher frequency for the reference level, the frequency response may have already started to roll off at that frequency.

Regards.

[pdenisowski]

One problem with using 0.35/T_rise is knowing in advance what the actual rise time of the pulse source is.

Another problem is that the "0.35" factor only applies when the scope has a Gaussian frequency roll-off.  A scope with a more flat or brick wall type frequency response would require the use of a higher number factor (usually 0.4 - 0.45).

Since almost all analog scopes have a Gaussian frequency response, 0.35 is commonly cited as the factor to be used when calculating bandwidth from rise time, but care should be taken if the shape of the scope's frequency response is not known.  Also, it's important to know whether "rise time" is being defined as the 10-90 or 20-80 interval.

In my experience, the easier and more accurate approach is to use the "amplitude of a sinusoid" method to determine the bandwidth of a scope.  The bandwidth <-> rise time relationship is best used when you already know the rise time of a pulsed signal and need to calculate the minimum required scope bandwidth to accurately measure that pulse.

[Performa01]

Another problem is that the "0.35" factor only applies when the scope has a Gaussian frequency roll-off.  A scope with a more flat or brick wall type frequency response would require the use of a higher number factor (usually 0.4 - 0.45).

You should avoid the term "brick wall" here, as no serious scope frontend will have a frequency response that is even remotely brick wall.

"Measuring" the bandwidth of a scope with a pulse is rather popular - maybe because the results sound so much better (and more impressive), if the Gaussian factor 0.35 is used for scopes with a more flat frequency response.

Another problem with the fast rise-time pulse (e.g. 40 ps) is that it might ask too much from the average modern DSO with less than 10 GHz bandwidth, where the Nyquist frequency exceeds the bandwidth only by a factor of 1.25 in full channel mode, as is very common today. This results in aliasing artifacts which in turn invalidate the rise time measurements. So care must be taken that the half (or even quarter, in cheap instruments) channel sample rate is utilized to avoid this pitfall.

At the end of the day, the good old levelled signal generator is still the preferred method to get a true and really informative picture. With modern DSOs and their advanced features we can even let the scope plot its own frequency response, see the example for the SDS2504X Plus below. And of course 1 MHz is the most commonly used reference frequency - in some cases like the example below (that goes up to 1 GHz) it can be desirable to have it a bit higher, so I chose 10 MHz back then. But thanks to the frequency plot we can clearly see that there are no significant differences below ~150 MHz, so this choice is legit. It might be different with an artificial bandwidth limit, which is implemented by a first order filter, so amplitude drop starts earlier.

[Martin72]

Otherwise if using the Bodnar pulser, it provides extremely fast edges @ 10 MHz

Besides the approximate formula (0.35/risetime), you could also try this:

https://www.teledynelecroy.com/doc/frequency-response-measurements

This didn't really work for me when I had a SDS2000X+, but since then 2..3 firmware updates have passed.
Maybe it works now.

Once again I'm too stupid to do it and can't get it to work on my HD, it looks just like it did on the X+.
But since 2N3055 showed it with an HD(didn´t find the thread so far), I assume it's my stupidity.

[BillyO]

"Measuring" the bandwidth of a scope with a pulse is rather popular - maybe because the results sound so much better (and more impressive), if the Gaussian factor 0.35 is used for scopes with a more flat frequency response.

Not quite true.  Obviously 0.35/Risetime is going to be LESS than 0.4/Risetime.

BTW, the SDS2000X-P scopes are definitely in the "flat" response category (at least when un-corked), so you should be using 0.4 which will give you more accurate (and more impressive) results than 0.35.

[Performa01]

"Measuring" the bandwidth of a scope with a pulse is rather popular - maybe because the results sound so much better (and more impressive), if the Gaussian factor 0.35 is used for scopes with a more flat frequency response.

Not quite true.  Obviously 0.35/Risetime is going to be LESS than 0.4/Risetime.

Thank you for pointing that faux pas out. You can tell that I've never worked with that formula, always used accurate frequency response measurements instead. There were several reasons that got my thinking wrong - ridiculous bandwidth claims being one of them.

BTW, the SDS2000X-P scopes are definitely in the "flat" response category (at least when un-corked), so you should be using 0.4 which will give you more accurate (and more impressive) results than 0.35.

Well, let's see how the formula accords to the data sheet for the various models:

Model       tr [ns]  BW real [MHz]  k [-]
SDS2104X+   3,50     100            0,350
SDS2204X+   1,70     200            0,340
SDS2354X+   1,00     350            0,350
SDS2504X+   0,80     500            0,400
SDS5034X    1,00     350            0,350
SDS5054X    0,70     500            0,350
SDS5104X    0,40     1000           0,400
SDS6054A    0,55     500            0,275
SDS6104A    0,35     1000           0,350
SDS6204A    0,23     2000           0,460

According to the datasheet for the SDS2000X+, the factor 0.35 would be accurate up to 350 MHz, i.e. for all artificially bandwith limited models/modes. According to this, factor 0.4 would be correct for the 500 MHz option. Now we all know that the bandwidth is significantly higher than specified for the SDS2000X+, so we can expect faster rise times too.

It is basically the same for the SDS5000X. The artificial bandwidth limit (which is just a first order lowpass) leads to a Gaussian frequency response, hence factor 0.35 in the data sheet. for the 1 GHz model, the natural roll-off of the input buffer and PGA lead to a more flat response, hence factor 0.4.

It looks very different for a higher bandwidth scope like the SDS6000A. The 0.35 factor fits for the 1 GHz model, but nothing else matches.