Rigol DS2072 delivers only 8bit values even in highres mode

[e61_phil]

Hello,

I connected my Rigol DS2072 via LXI to labview VISA. I would like to build some control VIs for the scope (I know, there are device drivers for labview, but the drivers use only BYTE mode).

I switched the scope in HighRes Mode and send

:wav:format word

The scope answers in 16bit values but the second byte is always 0x00 -> only 8bit resolution. (see attached picture). Is it impossible to get the 12bit HighRes values? But why is it possible to select WORD instead of BYTE?

Has anyone tried to get higher resolution than 8bit out of an rigol scope?

Thanks
Philipp

PS: The First 6 Words in the picture are data information. The first data word ist word number 7

[Teneyes]

Hi  HiRes mode on the DS2000 is a Boxcar Averaging of multiple samples , so I think you will have to write your own averaging program for the 8 bit samples you are receiving.

[e61_phil]

The scope delievers exactly the same amount of data in HighRes mode like in normal mode. So there are no extra samples I could average. And why should I select WORD mode if I have to throw away 50% of the data and average the rest on my own?

[Mark_O]

I switched the scope in HighRes Mode and send

:wav:format word

The scope answers in 16bit values but the second byte is always 0x00 -> only 8bit resolution.

Yes, that's correct.

Is it impossible to get the 12bit HighRes values?

Yes.

But why is it possible to select WORD instead of BYTE?

For compatibility with the SCPI command set, and tools that use it.

Has anyone tried to get higher resolution than 8bit out of an rigol scope?

Yes.  Unfortunately, there is no bank of memory to hold more than 8-bit samples.  So that's all that can ever be gotten.

[marmad]

The scope delievers exactly the same amount of data in HighRes mode like in normal mode. So there are no extra samples I could average. And why should I select WORD mode if I have to throw away 50% of the data and average the rest on my own?

The Rigol implements HighRes averaging between sample memory and display memory. Both are 8-bit memory, so once the averaging is done internally, the result is down-sampled to 8 bits again. If you want 12 bits (or anything >8 bits), you will have to read the sample memory and do the averaging in Labview. If you read the display memory, you're reading the already down-sampled high resolution waveform.

But just in case you're not aware of it, High Resolution mode (i.e. successive-sample averaging) produces the effects of a low-pass filter (or multiple notch filter):




...which equates to the following bandwidths when running on the DS2000:

[Mark_O]

But just in case you're not aware of it, High Resolution mode (i.e. successive-sample averaging) produces the effects of a low-pass filter (or multiple notch filter):

That's a cool graph.  I knew about the combing effect, but I hadn't visualized how deep the nulls actually were.  This is illuminating.  Thanks!