Rigol DS 1054Z behavior: normal or defective?

[_Wim_]

I ended up with a DSO more akin to a sophisticated data capturing device than a scope, and delivering so much more that I expected, but still can perform the basic functions of an analog scope with a believable display.

Can you share which DSO you are using? I am currently using a picoScope 5000 series for its high resolution, but the small signal performance could still use some improvement...

Ended up selecting the SDS2102X Plus which has exceeded my expectations in just about every way. It's been "enabled" with the kind help of folks here to 350MHz and just yesterday with help from tv84 to 500MHz which just quickly measured to 615MHz

I can't speak about other brands or Siglent scopes, but this SD2102X Plus is a stunningly good little DSO IMO. Wanted the 2104X+, but that was BO so settled for the 2102X+. The ADC they are using is quite good, much better than one would expect from an 8 bit device, I posted some statistics measurements and well you judge for yourself!

Here's some measurements from another thread.

First off DC measurements of the SDS2102X Plus input using statistics of C1

Input KS34465A of 5.00021VDC, DSO reads Mean C1 5.000398VDC (mean of mean)
Input of 10.00001VDC, DSO reads 10.0031VDC
Input of 7.04184VDC, DSO reads 7.04192VDC
Input of 0.99985VDC, DSO reads 999.39mvDC
Input of 100.0073mvDC, DSO reads 99.825mvDC

Now AC measurement with 50% duty cycle square wave of 5.00021V peak value, so Mean & StdDev (RMS) should be 5.00021/2 or 2.500011V

Input at 250Hz KS34465A 2.49993VAC, DSO reads 2.4916VDC (mean) and 2.5085VAC (stddev)
500Hz 2.49993VAC, DSO reads 2.4912VDC & 2.5094VAC
1KHz 2.49886VAC, DSO reads 2.4910VDC & 2.5095VAC
4KHz 2.49452VAC, DSO reads 2.4913VDC & 2.5092VAC
8KHz 2.48868VAC, DSO reads 2.4921VDC & 2.5085VAC

Note: The peak to peak readings of ~6Vpp include waveform ringing.

This is better performance than I would expect from this DSO

Don't know if I got lucky or this is typical performance from the SDS2102X Plus, maybe others could make some measurements


Here's snip on the ENOB & ERB behavior from another thread, which you can compare with other DSO scopes ENOB & ERB measurements by others.

Just did a quick test of the SDS2102X Plus in 8 bit, 10 bit, and ERES (3) modes using this as a means to evaluate Effective Resolution in bits. I'm not saying this is right or wrong way, just the way I chose to measure and calculate. Used 20MHz BW with 50 ohm in-scope termination, 1us/div sweep. Noise was averaged Standard Deviation to remove DC offset effects as mentioned.

Effective Resolution Bits (ERB) = {10*log[(8*(SF/N)^2 +1)] -1.76}/6.02, where N is Standard Deviation noise, SF is Scale Factor in V/div

Scale    500uv   1mv    2mv    100mv    200mv     500mv     1v
8 bit N  23.4uv  24uv  38.6uv  1.47mv  2.95mv    7.55mv    14.56mv
ERB     5.63      6.59    6.90     7.30      7.29         7.26        7.31

10 bit N 16.9uv  17uv   20uv   316uv    432uv      1.83mv    2.32mv
ERB     6.10      7.09     7.85    9.50      10.06       9.72        9.96

ERES N 12uv     12uv   14uv     132uv    190uv      725uv     860uv
ERB     6.59      7.59    8.37     11.60     11.89      11.80      11.39

FFT NF -122      -120   -120     -118      -108        -100        -97
in dBm

Added FFT noise floor in 8 bit mode using 2.5MSPS, 2097512 pts, delta f 1.19Hz and 16 average.

I computed these on my HP32 calculator, so hopefully no mistakes


Here's the thread for some other DSO ENOB measurements by Howard Long.

https://www.eevblog.com/forum/testgear/benefits-of-going-with-all-siglent-setup/msg3281580/#msg3281580



Best,

Those results do look quite impressive. I will give this a try this weekend on my Picoscope 5442B. How was the "standard deviation noise"-value measured? Is this the standard deviation on the measured AC pp value?

The smallest range on the Pico is 2mV/div (which is one of the disadvantages), so the lowest ranges I cannot do.

I theory it has a 16bit mode without ERES, and 20bit with ERES. In reality there is not so much difference between the 12 to 16 bit mode, but quite a bit of difference compared to the 8 bit mode. Due to the relative low bandwidth in 16bit mode (62.5MS/s), ERES will not by possible on a 1µs/div time scale.

[tautech]

Those results do look quite impressive. I will give this a try this weekend on my Picoscope 5442B. How was the "standard deviation noise"-value measured? Is this the standard deviation on the measured AC pp value?

The smallest range on the Pico is 2mV/div (which is one of the disadvantages), so the lowest ranges I cannot do.

I theory it has a 16bit mode without ERES, and 20bit with ERES. In reality there is not so much difference between the 12 to 16 bit mode, but quite a bit of difference compared to the 8 bit mode. Due to the relative low bandwidth in 16bit mode (62.5MS/s), ERES will not by possible on a 1µs/div time scale.

SDS2000X Plus have both a 10 bit mode (limited to 100 MHz) and a 3 bit ERES mode and both can be used together.
Early in the SDS2000X Plus thread Performa01 posted some screenshots about this.

[mawyatt]

Those results do look quite impressive. I will give this a try this weekend on my Picoscope 5442B. How was the "standard deviation noise"-value measured? Is this the standard deviation on the measured AC pp value?

The smallest range on the Pico is 2mV/div (which is one of the disadvantages), so the lowest ranges I cannot do.

I theory it has a 16bit mode without ERES, and 20bit with ERES. In reality there is not so much difference between the 12 to 16 bit mode, but quite a bit of difference compared to the 8 bit mode. Due to the relative low bandwidth in 16bit mode (62.5MS/s), ERES will not by possible on a 1µs/div time scale.

I doubt this will compete with the true core 16 bit ADC in your Picoscope.

Yes the SD is measured on the peak to peak value and then the statistics is the mean value of the SD. The AC waveform is almost a perfect square wave at these low frequencies up to ~500Hz with a max value set by a precision 5.000V voltage reference source used for VDD. The precision by design waveform was created from a 4.096MHz crystal osc. divided by cascaded CMOS Flip-Flops which drive a discrete CMOS inverter with low Rdson N and PMOS devices. The SD, RMS are the same and so is the MEAN or DC term and ideally should be 1/2 the VDD voltage reference.

Best,

[_Wim_]

I doubt this will compete with the true core 16 bit ADC in your Picoscope.

I agree that this unlikely for the higher voltage ranges (where the true advantage of the 16 bit can be used), but I suspect this will be the case for the 2 and 10mV ranges and probably even beat it. For these small signals I wish the pico was a little better...

[2N3055]

I don't have 54xx series Pico. But on my 4262, most sensitive range is also 2 mV/div.
But noise is less than 10uV RMS, you can software zoom in 16 times and still have 4000 points vertically, and have 125uV/div on screen...
I guess 54xx series noise would be higher (4262 is only 5MHz bandwidth), but you could still software zoom in 4x with very usable results... And that would be 500uV/div, very respectable number..

[_Wim_]

I don't have 54xx series Pico. But on my 4262, most sensitive range is also 2 mV/div.
But noise is less than 10uV RMS, you can software zoom in 16 times and still have 4000 points vertically, and have 125uV/div on screen...
I guess 54xx series noise would be higher (4262 is only 5MHz bandwidth), but you could still software zoom in 4x with very usable results... And that would be 500uV/div, very respectable number..

The 4262 is a far far lower noise device than the 54xx series scope. That is a true 16-bit device, while the 54xx are 12-bit devices that use some interleaving tick of the 4 channels to supposedly achieve 16-bit. But in practice the difference between 12-bit and 16-bit mode is not very high, so I do typically use it in the 12-bit mode (when no bandwidth limit filter is used, you do see more “improvement” of the 16-bt mode, but that is just due to the reduced bandwidth)

Don’t get me wrong however, the pico 5442 is still a fantastic high resolution device, just the lower range is a bit noisier than I would like (with a pre-amp this is ok), and it is for sure not a 4262. I would love the have a 4262 in my collection also, but so far not have come across a good deal on one of those, and buying a new one on top of my 54xx seems not worth is, as with a pre-amp I can do most things I need any-way.

[2N3055]

I don't have 54xx series Pico. But on my 4262, most sensitive range is also 2 mV/div.
But noise is less than 10uV RMS, you can software zoom in 16 times and still have 4000 points vertically, and have 125uV/div on screen...
I guess 54xx series noise would be higher (4262 is only 5MHz bandwidth), but you could still software zoom in 4x with very usable results... And that would be 500uV/div, very respectable number..

The 4262 is a far far lower noise device than the 54xx series scope. That is a true 16-bit device, while the 54xx are 12-bit devices that use some interleaving tick of the 4 channels to supposedly achieve 16-bit. But in practice the difference between 12-bit and 16-bit mode is not very high, so I do typically use it in the 12-bit mode (when no bandwidth limit filter is used, you do see more “improvement” of the 16-bt mode, but that is just due to the reduced bandwidth)

Don’t get me wrong however, the pico 5442 is still a fantastic high resolution device, just the lower range is a bit noisier than I would like (with a pre-amp this is ok), and it is for sure not a 4262. I would love the have a 4262 in my collection also, but so far not have come across a good deal on one of those, and buying a new one on top of my 54xx seems not worth is, as with a pre-amp I can do most things I need any-way.

I totally understand you. I had old 212/100 pico, a 12 bit device, and that was already a huge improvement over 8 bitters...
If I had 54xx series Pico I probably wouldn't have gotten 4262. But I have 3406D and Keysight 3000T, and 4262 was the thing to complement those two on high precision, low noise, low frequency end. I had a project that benefited from it, so I got it.

[alsetalokin4017]

Hi All,

I've been doing electronics as a hobby since I was a teenager 40+ years ago, and decided it was finally time to retire my 1970s Tektronix 2-channel CRT scope.  After a few minutes of on-line research I ordered a Rigol DS 1054Z (with 24 Msamples memory and all possible options enabled the price was still low) which arrived earlier today.  I've been playing around with it for a couple of hours, and am impressed by what it can do.

One odd thing I have noticed: if I look at the built-in calibration signal (1kHz square wave, 3v amplitude) the horizontal traces at 0 and 3v look broader than in the manual.  If I zoom in on them, I can see that they are each made of a pair of lines of equal brightness, separated in amplitude by tens of mV.  I'm not sure how many bits are used internally, but I guess this might be quantization noise from the input ADC.  I can also see this if I (electronically) ground the input.  I would have hoped that the electronics noise at the input is not enough to dither the ADC.  I've also noticed that as I shift the position of the trace vertically, the relationship between the two lines shifts and distorts.

My question: is this behavior "normal" or did I get a scope with a bad input amplifier or noisy ADC?  Easy to send it back now, if that's the case.

Cheers,
   Bruce

Edit: when I shift the vertical gain from 500mV per division to 200mV, I can hear a relay click shut internally.  That's when the shape of trace near zero distorts and becomes dependent on the Y-axis offset.  I don't think this should happen, is it "normal"?  Also, I can see the doubling of the horizontal trace lines when the gain is set so that 3V is full scale, so it's got to be at least 30 mV, meaning that it's in the 8th or 9th bit of an ADC.

Here's a photo of the calibrator signal, I have turned off the display grid to make the structure more visible:

(Attachment Link)

Sorry it took me so long to view this thread.

I am unable to replicate the double trace. I've tried everything I can think of. Any suggestions, while I still have the scope set up?
(00.04.04.04.02)

[ Specified attachment is not available ]

[alsetalokin4017]

In the photo attached to my original starting post in this thread, there are three "non-standard" settings, intended to make the effect clearer and to prevent my camera from saturating.  Miti, Tom66, could you please try this one more time but with exactly the settings I have used?  To ensure this, first set the scope to default settings by putting

Utility->System->Power Set=default and power cycle.

Then input the calibration signal on channel 1, use "Auto" to pick trigger/timing/gains, and set

Display->Type=dots
Display->Grid=off
Display->Intensity=25%

Last step, shift the vertical position up and down.  I am starting to think that what I am seeing here is just the discrete quantization of levels from the 8-bit ADC.  Meaning: I have the vertical position set so that the max and min square wave values split between two adjacent ADC output steps, and the display algorithm has each ADC output step illuminate only half the pixel height to the next output step. Hence a black band appears between adjacent ADC levels.

Done all that, unable to replicate double trace, see screenshot above.   

[alsetalokin4017]

To me this seems like a horrible show-stopping software or hardware bug.  I presume the latter since otherwise it would have been fixed long ago.  Can you really learn to live with this?

I say it again: I never saw a double line on mine at ordinary zoom levels. Other people here are also saying they don't see this under these conditions. If you have a chance to exchange yours then do so.

I agree, I think. At least, as long as I can't reproduce the OP's original double trace, I have to conclude that there is something wrong with his, or something right with mine.   

[alsetalokin4017]

Interlude: Artifact art?

[alsetalokin4017]

Trace is singular and well behaved at all zoom levels.

[Fungus]

Trace is singular and well behaved at all zoom levels.

Yep. I'm sticking with "defective scope, send it back for a replacement".