REVIEW - Rigol DS2072 - First Impressions of the DS2000 series from Rigol

[Galaxyrise]

How are you getting a continuous trace of closely spaced dots?  You should be seeing only one dot per horizontal division (1 ns/div, 1G samples/second).

Looks like hi res acquisition

[JDubU]

How are you getting a continuous trace of closely spaced dots?  You should be seeing only one dot per horizontal division (1 ns/div, 1G samples/second).

Looks like hi res acquisition

Ah yes!

[alank2]

Does anyone have a good description for how the hi resolution mode works?  The manual didn't really help me understand it.

[Carrington]

Does anyone have a good description for how the hi resolution mode works?  The manual didn't really help me understand it.

Please search on the forum, because it has already been discussed in detail.

[PA0PBZ]

Looks like hi res acquisition

Ah yes!

Yes it is in hi res because the original from EV was also in hi res.

[Carrington]

Yes it is in hi res because the original from EV was also in hi res.

Please can you repeat the same test for 1ns/div, but not in stop mode and/or hi res.
Thanks.

[marmad]

Does anyone have a good description for how the hi resolution mode works?  The manual didn't really help me understand it.

Yes it is in hi res because the original from EV was also in hi res.

At those time bases in HighRes, the DSO is just doing sin(x)/x interpolation and filling in the display memory with points instead of vectors. It does absolutely nothing that Normal mode and sin(x)/x don't do - except display the trace dotted.

[marmad]

Bandwidth DS2302 HW 2, signal generator on 1 volt, 10 Mhz steps:

Sorry, but I'm not sure I buy this BW chart.

If the filter is really only ~-5.5dB down at 500MHz, I believe the DSO will run into problems with sin(x)/x interpolation - which is highly susceptible to errors if the original signal contains frequencies higher than the Nyquist frequency. With 2 channels turned on and a 1GSa/s rate, the Nyquist frequency is 500MHz.

According to previous BW charts posted, the original DS2202 was ~-16dB down at 500MHz. Having a slower roll-off and a higher passband is NOT a good thing if the rest of the hardware doesn't support it.

[PA0PBZ]

Sorry, but I'm not sure I buy this BW chart.

Atttached Excel sheet with the measurements.

[PA0PBZ]

Hmm, this is indeed a bit 
Just turning on the grounded channel 2 kills the channel 1 waveform:

[marmad]

Sorry, but I'm not sure I buy this BW chart.

Atttached Excel sheet with the measurements.

Well, I believe you made measurements and a chart - but that doesn't mean it's accurate.     Hell, you had HighRes mode on - which is an averaging technique, and thus a filter - which would normally be the last thing you should do if trying to accurately measure bandwidth.

But, IMO, if your measurements ARE correct, I'd say Rigol made a mistake in redesigning their filter - and it makes me feel better about owning a HW v.1

[PA0PBZ]

I just had hi res on for the other screenshots because I figured that EV had it on too (too many dots) in his original posting and I switched it off after taking the shots. Not sure what is going on, going to test my sig gen now 

[EV]

I got explanation to this from TEK Forum:

"When at 400ns/div or faster horizontal time base, the sample rate is maxed at 2.5GS/s. To overcome the max sample rate, the instrument goes into real time interpolate mode and mathematically adds points depending upon the horizontal time/div setting. What you are seeing are the interpolated points, not actual samples."

My old TEK TDS3032 has 2.5 GS/s and 5 samples per division with 1 ns time base. It is so regardlss whether both or only one channel is on.

But that doesn't make sense mathematically. If 2.5GSa/s is the maximum rate, 400ps is the smallest sample period. That would be 2.5 samples per div @ 1ns. 5 samples per div would require a 5GSa/s rate (200ps sample).

[marmad]

I just had hi res on for the other screenshots because I figured that EV had it on too (too many dots) in his original posting and I switched it off after taking the shots.

Ok, sorry, my mistake.

Again, I have no problem if the -3dB BW is up around 350MHz - but the rolloff according to your chart is so slow I think problems could arise with signal reconstruction.

Compare it to the rolloffs in the two bandwidth charts posted on this page.

"...and mathematically adds points depending upon the horizontal time/div setting. What you are seeing are the interpolated points, not actual samples."

Which is basically what the Rigol is doing in HighRes mode below a certain time base.

[Carrington]

I got explanation to this from TEK Forum:

"When at 400ns/div or faster horizontal time base, the sample rate is maxed at 2.5GS/s. To overcome the max sample rate, the instrument goes into real time interpolate mode and mathematically adds points depending upon the horizontal time/div setting. What you are seeing are the interpolated points, not actual samples."

A few days ago someone mention something about a Tek oscilloscope that in dots mode showed more samples than should be.
It's not magic, are interpolated (maths).

https://www.eevblog.com/forum/testgear/sniffing-the-rigol%27s-internal-i2c-bus/msg355318/#msg355318

[Carrington]

But, IMO, if your measurements ARE correct, I'd say Rigol made a mistake in redesigning their filter - and it makes me feel better about owning a HW v.1

DS2072, DS2072 (HW2.0) and DS2072A have all different input stages.

[Carrington]

And no idea why this happens: 



@ PA0PBZ: Thanks.

[marmad]

DS2072, DS2072 (HW2.0) and DS2072A have all different input stages.

Yes, clearly I know that. But if PA0PBZ's chart is accurate, IMO it indicates a poorly designed filter for the sampling hardware.

[JDubU]

And no idea why this happens: 

What does it look like when switched to "Dots" mode?

[Carrington]

Yes, clearly I know that. But if PA0PBZ's chart is accurate, IMO it indicates a poorly designed filter for the sampling hardware.

Well, who knows, it may be an error in the measurement.

[Galaxyrise]

And no idea why this happens: 

I'm unable to infer from that screenshot what is surprising to you.

[Carrington]

I'm unable to infer from that screenshot what is surprising to you.

Why do you think that there is nothing unusual?

[PA0PBZ]

What does it look like when switched to "Dots" mode?

Dots mode is ok.

[EV]

There are too few sample points for Sin(x)/X interpolation.

And no idea why this happens: 

[Teneyes]

Hi All
  To Help show how DS2000 makes vectors out of sample points. I have constructed waveform files that have a low number of sample points. The sample points are calculated perfect sin values. I have chosen repeating patterns. I show 6, 4 and 2.5  sample points per cycle and at 1GSa/s.  You can see how the DSO interpolates the sin in the vector displays

These are stopped displays,  In run mode the varying trigger scanning causes the sampling to collect a series of sample along the sin display and if not a sin wave(step function) the DSO will create a sin wave overshoot.

Note : At 2.5 samples/ cycle the frequency will be accurate but Vpp is NOT.
   AS EV says very few points