1         SIGLENT SDS1102CM 2x100MHz, 2x500Msa/s, 2x1Msa memory depth oscilloscope review

(Larger image)

 

Where I found some faulty operation, or function that is useable only with special oscilloscope settings I colored the text to dark red.

 

If you are interested in the usability of any additional feature or you found any of my tests faulty, or you have a better idea for using any function please mail me. I will try it if I have the possibility and add it to the review.

 

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1.1      Instruments used

 

SIGLENT SDS1102CM

Specifications

Based on the CSV file:

Model Number:                     SDS1102CM

Serial Number:                     SDS00002111512

Software Version:                3.01.01.22

Based on the turn on screen:

Software Version:                3.01.01.223

Approx. 450USD on ebay.com

 

Agilent Technologies DSO6054A

Specifications

500MHz

4Gsa/s

4Msample/ch memory depth

7000USD on ebay.com

 

Agilent Technologies DSO-X 3024A

Specifications

1channle: 4Gsa/s (Interleaved)

2-4channel: 2Gsa/s

200MHz bandwidth

Approx. 3500USD at hu.rs-online.com

1.2      Bandwidth limit

I tested the bandwidth limit by an 1Vpp sine wave at 100MHz. The reference instrument was a Tektronix 500MHz oscilloscope. The display at 10MHz was identical on the two scopes. At 100MHz I measured about 0.7Vpp on the SDS1102CM, while the Tektronix still measured 1Vpp. The bandwidth limit of the SDS1102CM is really 100MHz

1.3      Memory depth

The memory depth is 1Mpoints/channel, as it can be seen from the CSV file header. See the spectrum measurements. The point in this test is to analyze that if I stop the acquisition than how detailed information can be seen in the signal by zooming into it.

 

This is an SPI communication at 8MHz clock. In a 25us/div setting one packet of data does not fill the screen. The packet time (16 byte) is about 32us, so the screen is now about 150 bytes long. (Plus the dead time.)

 

Settings

-          Memory Depth: LongMem

-          Trigger: Normal

 

Zooming on one byte of data, the data can be read from the screen, but it is at the very limit. (Data clocked by rising edge, 00010100)

 

The zoom ratio is 25us/100ns = 250

 

 

Here is the same view extracted from the 2x1Mpoint CSV file by Matlab. So what can be seen on the picture that is really the whole information in the memory.

The signal in Matlab seems to be more smooth, some extra oscillations are missing from it. This is caused by the “sinx/x: sinx” setting. If I set it to “x” the oscillations disappear and we can see the pure data. This seems to be identical to the Matlab curve.

Now the same packet fills the screen.

Examining only one byte is quite easy by zooming on it.

 

The zoom ratio is 5us/100ns = 50

 

The signal is stopped by pressing the SDS1102CMs STOP button in NORMAL trigger mode. It must be noted that if I stop it in SINGLE trigger mode the result is much less useable, although the two should be equivalent. I can not reproduce this error.

 

It must be also noted that the 2Mpoints memory depth works only at 50ms/div and faster time/div settings.

I got the information that in earlier firmwares (1.01.01.07R13) the signal saved in SINGLE mode is less detailed than if the signal is stopped by the STOP button.

 

I tested the memory depth again by stoping the signal with the SINGLE button, or switching the trigger mode to SINGLE. Both cases I got the same detailed picture as in the above case. This is the header of the CSV file saved in SINGLE mode. The record length is 1048576 points per channel.

Record Length,1048576,,Source,CH1,CH2

Sample Interval,CH1:0.0000000100000 CH2:0.0000000100000,,Second,Volt,Volt

Vertical Units,CH1:V CH2:V,,-0.00524288000,0.00,4.32000

Vertical Scale,CH1:2.00 CH2:2.00,,-0.00524286969,-0.08000,4.32000

Vertical Offset,CH1:2.00000 CH2:-6.16000,,-0.00524286000,0.00,4.24000

Horizontal Units,s,,-0.00524284969,0.08000,4.24000

Horizontal Scale,0.0000050000,,-0.00524284000,0.00,4.32000

Model Number,SDS1102CM,,-0.00524282969,-0.08000,4.32000

Serial Number,SDS00002111512,,-0.00524282000,0.00,4.24000

Software Version,3.01.01.22,,-0.00524280969,0.00,4.24000

,,,-0.00524280000,0.00,4.24000

,,,-0.00524278969,0.00,4.32000

,,,-0.00524278000,-0.08000,4.32000

,,,-0.00524276969,0.00,4.16000

,,,-0.00524275969,0.00,4.16000

 

1.4      Sampling rate and “dots” display

 

Settings

-          Memory Depth: LongMem

-          2 channel

-          2.5ns/div

-          Stopped by SINGLE button

-          Display/Type: dots

 

The sampling rate displayed by the SaRate field in Acquire menu is 250Msa/s.

 

I expected 500Msa/s in the fastest time/div setting with two channels active.

 

The cursor reads between two displayed samples 500MHz. Maybe, the SaRate field is wrong…

 

If I stop it by the STOP button I get a faulty display, see later…

I’d like to see 1Gsa/s, so I turned off CH2. Now the SaRate field in Acquire menu is 500Msa/s.

 

Here it is stopped by the SINGLE button, so the correct data can be seen. The distance of the dots is also correct.

Here it is stopped by the STOP button, so the displayed data is faulty like with the previous settings.

I turned off the LongMem.

 

Settings

-          Memory Depth: Normal

-          1 channel

-          2.5ns/div

-          Stopped by SINGLE button

-          Display/Type: vectors

 

 

 

If I turn the vectors off I can finally see 1Gsa/s in the SaRate field and on the screen also.

 

The STOP/SINGLE problem is also solved, I see the same if I stop it either way.

 

1.5      Equivalent time sampling

 

This is the falling edge of the previous SPI clock and the rising edge of the data.

 

On the running picture there is not big difference between the two interpolation settings. (Sinx/x = x or sinx)

 

Also there is no difference between Display Type = Vectors or Dots, although there should be difference, because in this case one sample is taken only in every 2ns. If the sampling is stopped the dots can be seen.

 

Settings

-          Memory Depth: LongMem

-          Trigger: Normal

-          Mode: Real Time

 

If I switch to Mode: Equ Time I have to wait 10 seconds to get this display.

 

It seems as if the signal was recorded in a much slower time/div setting. This must be some software fault.

 

1.6      Undersampling

I use a 15.041kHz sine wave.

 

Settings

-          Acquire: Sampling

-          Trigger: Normal

 

The signal is stopped at 500ms/div. In this setting no undersampling can be seen. The signal is a yellow strip.

 

If I zoom into it to 5ms/div I can see it to be a 45.05Hz sine wave.

 

This effect is a consequence of the sampling theorem, but care must be taken.

Let’s justify this with the Agilent. The Agilent has an “antialiasing” function that can be switched off. Its own calibrating signal (1.2kHz) can not be undersampled in any time/div setting.

 

This is a 27MHz clock signal.

With the antialiasing turned off, and the signal stopped at 200ms/div, zooming into it the undersampling can be seen.

 

If the antialiasing is ON, than we get some sawtooth signal at the same amplitude, that I don’t understand, but at least it can not be mixed up with a 95.7Hz clock…

 

1.7      Trigger

 

The signal is the calibrating signal of the SDS1102CM. 3Vpp, 1kHz

 

Settings

-          Trigger: Normal

-          Trigger level: 1.12V

-          Trigger edge: falling

-          Stopped by STOP button

 

I should be able to see a falling edge at the trigger point.

If I set the trigger level slightly higher the display gets better, but far from perfect.

 

Settings

-          Trigger level: 1.68V

 

The level is not changed, just the time/div setting. The signal is still stopped by the STOP button. The trigger edge is still falling! In this case the running signal is jumping in time, as if there was no trigger at all.

Same settings, but the signal is stopped by SINGLE button.

 

Seems to be good. While running it is still similar to the previous picture.

 

1.7.1      Trigger point

 

Although in the “Equivalent time sampling” chapter it was clear that the falling edge of the signal crosses the trigger level at the trigger time point, there are problems with the trigger time point in many settings.

 

Settings

-          Trigger: Normal

 

The SPI data packet is stopped here with the STOP button. While the signal is running the trigger is at the first rising edge of the yellow channel, but if it is stopped it waits about half second, and makes last sweep. But the trigger time is not correct.

If I stop the same signal by SINGLE mode than the trigger point is in the right time.

 

In different settings it happens that the SDS1102CM forgets to display the signal at the trigger point.

 

1.7.2      Pre triggering

 

The trigger point is pushed to the left by 31.54us. In this time/div setting (250ns/div) the trigger point is on the very left side of the record as it is shown by the red ’T’ at the top of the screen. The trigger point can not go out of the record, so further decreasing the time/div is not possible.

If I still try it I get some false result. Neither the signal display is correct, nor the trigger point mark at the top of the screen.

 

1.8      Dual time base, Delayed signal

 

Instead of the pre trigger the dual time base can be used. I still use the SPI communication. 16bytes in every 10ms, as it can be seen on the top of the screen.

 

Settings

-          Memory Depth: Normal

 

On the bottom it does not turn out that one packet is 16 bytes. The signal at the bottom is about 50us long, although the data packet lasts only to 32us.

 

On the bottom some trigger problem can be seen. The green trigger point is far from the beginning of the signal.

Settings

-          Memory Depth: LongMem

 

This, or something similar useless and very faulty display can be seen at changing to LongMem, every time changing the delayed signals time/div setting, after pressing STOP, and most of the times pressing the SAVE button.

After pressing STOP twice (stopping and restarting the display) this is the running display. If I press SAVE, mostly I get the previous type of picture, but sometimes a good one can be caught.

 

The running picture seems to be perfect. The length of the data packet is correct

How about resolution? I still can only catch the signal by pressing SAVE until I get a good display.

 

The resolution is much better than in pre-trigger mode, or by zooming on the stopped signal. The time/div ratio is 5ms/25ns=200000

 

1.9      FFT, spectrum measurement

1.9.1      How can I get the instrument to show a very simple spectrum

 

A 15kHz sine wave.

Settings

-          Memory Depth: LongMem

 

I just turn on the FFT.

Settings

-          Zoom: 1x

-          Cursors: 10MHz, 20MHz

 

 

From the cursor readouts it can be seen, that this FFT is useless. Frequencies in the 10MHz range can be read from it, but the 15kHz can not be seen.

 

 

I change the sec/div setting to 50ms/div. It can be seen in the Undersampling chapter, that this oscilloscope can undersample the signal. (For any setting change in the time domain signal I have to turn the Math channel off, otherwise the buttons set the FFT.)

 

There is nothing around 15kHz as the cursor shows.

 

Go back to a non-undersampling time/div setting, although in this setting the signal can not be seen, only a yellow strip.

Settings

-          Time/div: 1ms/div

-          FFT zoom: 10x

 

There is a big peak on the spectrum, but it is at 600kHz, and the 15kHz peak still can not be seen.

 

Settings

-          Memory Depth: Normal

 

Now the 15kHz component can be clearly seen.

 

It must be noted, that the spectrum is the same as in the „LongMem” case. I have no explanation for this, but it is misleading.

 

 

1.9.2      Comparison of the spectrums and the CSV file

 

This is a 1kHz, 3Vpp squarewave, the calibration signal of the SDS1102CM.

 

The target is to compare the spectrum calculated by SDS1102CM and by Matlab on a PC using the CSV export of the scope.

I measure the spectrum of this signal based on the experiences of the previous chapter.

Settings

-          Window: Rectangle (Because I will use the same in Matlab)

 

The data of the first peaks is the following:

1.01kHz: 4.8dBV

3.01kHz: -3.2dBV

(difference: 8dB)

 

I suppose these values are correct. The difference should be 9.62dB, but the error of the reading is big, and the squarewave can be imperfect.

Settings for CSV save:

-          Para Save: On (I suppose this inserts the settings in the beginning of the CSV file)

 

This is the header of the CSV file. The Normal Memory Depth results 20480 points. Other info: 20us/sample, 25msec/div, 1V/div, etc…The first column is the time, not the spectrum!

 

I examined a Long Mem CSV header, the Record Length was 2097152 points for one channel and 1048568 for two channels. The file size was about 57MB, the saving to the USB pen lasts about 5 minutes.

Record Length,20480,,Source,CH2

Sample Interval, CH2:0.0000200000016,,Second,Volt

Vertical Units, CH2:V,,-0.20480001563,0.04000

Vertical Scale, CH2:1.00,,-0.20478001563,0.04000

Vertical Offset, CH2:0.00,,-0.20476001563,0.04000

Horizontal Units,s,,-0.20474001563,0.04000

Horizontal Scale,0.0250000000,,-0.20472000000,0.08000

Model Number,SDS1102CM,,-0.20470001563,0.00

Serial Number,SDS00002111512,,-0.20468001563,0.08000

Software Version,3.01.01.22,,-0.20466001563,0.04000

,,,-0.20464001563,0.04000

,,,-0.20462000000,3.12000

,,,-0.20460000000,3.12000

,,,-0.20458001563,3.12000

,,,-0.20456001563,3.12000

,,,-0.20454001563,3.12000

,,,-0.20452001563,3.12000

,,,-0.20450000000,3.12000

,,,-0.20448000000,3.12000

,,,-0.20446001563,3.08000

Out of the data of the CSV file the Matlab calculates this spectrum.

 

The sampling frequency is 50kHz, the number of points is 20480, so in the spectrum one point (horizontal axe) is 2.4414Hz. The data of the first two peaks:

1003.41Hz: 15207

3002.92Hz: 6287

The difference is: 7.67dB

 

The 8dB difference measured by the SDS1102CM is exact.

 

1.9.3      Spectrum measurement on complicated signal

 

The signal is the voltage on a small electric motor in AC coupling. A 22ohm resistor was serial connected with the motor to make the voltage ripple more visible. The base frequency seems to be 51.02Hz. (See cursors)

 

So I expect a base harmonics at about 50Hz, and one harmonics at every odd multiple of it (150, 250…). And I expect a higher harmonics at every even multiple also, because visually the signals frequency seems to be 100Hz.

In the FFT nothing can be seen.

 

Settings

-          Window: Rectangle (Because I will use the same in Matlab)

 

I could not find a time/div setting where the spectrum is visible although if I stop the signal at 1s/div and zoom into it the waveform can be seen. So I suppose the SDS1102CM does not use the whole data in the memory to calculate the spectrum.

I will calculate the spectrum with Matlab. This is the first 1000 point in a CSV file saved with 100ms/div setting. In this case the largest possible resolution of the FFT on the SDS1102CM is 625Hz/div. So the 50Hz base frequency can not be seen.

 

The base period is about 510points, the sampling period was 40us. So the period is 20.4ms, and the frequency 49.01Hz.

This is the whole FFT of the CSV data.

One point is Fs/20480=1.2207Hz

This is the first 300 points of the FFT.

 

The peaks are at (from the detailed Matlab analysis):

50.04Hz

98.87Hz

148.92Hz

 

So saving the signal in CSV and analyzing by Matlab gives a very useable result. The FFT of the SDS1102 is not useable for this.

 

1.9.4      The same signal on a “more” expensive scope

 

 

I tried the same measurement on the Agilent oscilloscope.

 

The base harmonics is 65.6Hz

There is a possibility to zoom on the interesting part of the spectrum, but the base harmonics can not be seen. X1 cursor is at 64Hz.

 

Settings

-          Window: Rectangle (Because the same was used on the SDS1102CM)

 

The reason can be the rectangular window function. Only some periods are in the window, and the window width is not a multiple of the period.

If many periods are in the window the spectrum can be seen as it is expected.

 

I suppose the selected part of the spectrum, about 500 point is calculated from the 4Mpoints stored in the memory.

 

1.10Save

1.10.1 Waveform save

Recalling a saved waveform

-          It loads the saved screen with the settings and stops the display

-          Zoom and delay can be adjusted, approximately according to the Normal MemDepth even if the waveform was saved in LongMem setting

-          If I press the STOP button to start the scope, the saved waveform disappears. It can not be compared to the running signal, but it can be saved to picture or CSV

-          When saving while the signal is running it happened (sometimes) that the saved signal jumps somewhere else.

-          At recall sometimes nothing is loaded

1.11REF

The below case was the only one when I could display the reference signals. At any other try I pressed the SAVE button on the REF menu it says “Store Data Success”, displays the “A->” symbol that marks the zero level of the REF signal, displays that the REF is ON in the menu and DOES NOT display the signal.

 

Switching between REFA and REFB must be done on the running signal. If it is done on the stopped signal, the signal jumps in time, so something else will be saved.

 

The displayed reference signals can be saved to picture or CSV.

 

The reference signals do not zoom by setting the time/div.

 

 

1.12Noise, Offset

The most sensitive settings:

1x probe:                    2mV/div,

10x probe:                 20mV/div

 

In the tests I always adjusted the probe setting in the CH1 menu according to the physical probe setting. With both 1x and 10x probe setting at the most sensitive V/div the bandwidth limit is automatically turned on, and can not be turned off. In the second most sensitive setting (5/50mV/div) it can be set to be off.

 

Right after turning on the oscilloscope with both 1x and 10x probe setting the offset of the scope is 1 div (2/20mV) even in AC coupling. The noise is about 0.5 div peak to peak.

 

The following tests were done after 20 minutes warming up.

 

I connected a 28.8ohm(DC) resistance earphone speaker to the probe, and whistled in it.

 

Settings

-          1x probe

-          2mV/div

-          AC coupling

 

Keeping the above settings I shorted the input of the probe.

 

A slight offset can be seen, and a small noise. The same can be seen in DC coupling.

Same settings as above, but with 10x probe.

 

The result is the same.

The same settings again, but after an automatic calibration.

 

The noise is much smaller and the offset can not be seen.

 

So if noise is critical it is worth to make a calibration.

 

 

1.13Signals around the badwidth limit of the scope

An application note of Agilent states that sampling fidelity can often be more important than maximum sample rate. For evaluating sampling fidelity I used one single output of a 155.52MHz VCXO. This VCXO is supposed to output a square wave, the amplitude is about 200mV. I connected an LC network to it to amlify the fundamental frequency to receive a sinewave. The output of the LC network wa finally not useable, but it was good for comparing the SIGLENT SDS1102CM to the Agilent DSO-X 3024A.

 

1.13.1 Measurements with Agilent DSO-X 3024A

Theoutput of the VCXO. The bandwith of this scope is 200MHz, so the amplitude of the fundamental harmonics must be real here. About 400mVpp.

 

Settings

-          AC coupling

-          Window: Hanning

-          10ns/div

-          Sampling: 4Gsa/s, since only one channel is on, the sampling is interleaved.

-          FFT: 0 – 1GHz, 100MHz/div

 

No problem can be seen on the signal, no distortion. It seems to be sine, although the spectrum shows some harmonics.

The haronics are the multiples of 157MHz: 157, 310, 466, 646, 955

 

The application note says that the error of the interleaved sampling causes harmonics at Fsampling-Fsignal. Where Fsampling is the sampling frequency of one AD converter of the two. That would be here about 1.85GHz. This can not be seen on this picture.

 

If I turn on the bandwith limit for channel 1 the signal totally disappears, as it is expected

This is the output of the LC filter in 10ns/div again. It is quite noisy, the spectrum does not show any 155MHz harmonics.

 

A 100MHz peak can be seen on the spectrum, and some slight feeling of a 100MHz sine on the time domain signal.

Here the same signal is averaged out of 256 shots.

 

The amplitude can not be measured, but the spectrum is interesting. It is clear that there is the fundamental frequency of the VCXO.

 

Additional frequencies are at the multiples of 100±10MHz. I suppose this is the error of the signal source.

1.13.2 The same signals measured by the SDS1102CM

 

This is the output of the VCXO. The signal is jumping, two shots are always different, many shots can be seen on the screen in the same time.

 

The memory depth is Normal, otherwise the sampling rate is only 500MHz, and no interleave error could be seen.

 

Settings

-          AC coupling

-          Sampling: 1Gsa/s, since only one channel is on, the sampling is interleaved.

-          Sinx/x: x

 

 

Here is the above signal stopped.

 

On the Agilent this was a sinewave with a constant amplitude, but this signal is over the specification of this scope.

When turning on the averaging a constant sinewave and the jumping shots can be seen in the same time. If I stop the signal the averaged constant sine disappears and I get the same as in the above picture.

 

Settings

-          Averaging: 128

 

The output of the LC filter. Unlike the Agilent the SDS1102CM shows a significant amplitude. Is it +1 point for the Siglent!

 

The amplitude is approximately 60mVpp.

If I turn the bandwidth limit on, the amplitude is still about 30mVpp, although the signal should disappear.

 

It can be stated, that the 100MHz could be seen on the Agilent scope also.

The output of the VCXO again. It seems like amplitude modulated. I suppose this is the result of the SDS1102CM sampling system.

I turned the Sinx/x interpolation on, to see how distorted is the signal when using the 1GHz interleaved sampling of the scope…

… and I compared to the 500MHz non interleaved sampling. (CH2 is on)

 

I can see no difference. According to the application note this shows no error in the sampling system. Or at least it can not be seen

This is the spectrum of the VCXO output. It is very similar to the LC filter output on the Agilent… I have no idea why.

 

Spectral components can be seen at 156MHz and its multiples (312, 468). Also there are lines at 100MHz and its multiples, which also appeared on the Agilent scope.

 

But here a 344MHz component can also be seen which is the difference of the sampling frequency of one AD and the fundamental frequency of the signal. This shows some alignment error in the interleaved sampling.

The spectrum of the output of the LC filter does not contain the 156MHz. (Like on the Agilent without averaging) but it contains the 100MHz and its multiples.

 

On the SDS1102CM I can not use the averaging function for getting a more clean picture, because it does not work for the FFT

 

As it is measured on both scopes this can be the error of the signal source.

1.13.3 A 66MHz clock, that the SDS1102CM can deal with

 

The signal seems to be a sinewave, although it is a squarewave. This is normal, the harmonics are filtered.

 

The multiples of 66MHz can be seen.

 

I can’t explain the multiples of 33Mhz that can also be seen.

 

The amplitude of the harmonics is decreasing, except around 433MHz. I suppose this part is caused by the misalignment of the interleaved sampling.

1.14Display problems

 

While the signal is running and the scope is set to dot display mode the dots are very dense on the screen. As if it was some equivalent sampling mode.

 

When I stop the signal it shows the normal density of dots.

 

The averaging function works only while the signal is running, and it works only in AUTO trigger mode. See the figures in the “The same signals measured by the SDS1102CM” chapter.

 

1.15Edit history

 

03.01.2012.

First version

05.01.2012.

“Noise, Offset” added

10.01.2012.

“Sampling rate and “dots” display” and  “saved signal detail in single mode test” added

13.01.2012.

“Signals around the bandwidth limit of the scope” added

“Display problems” added