MATLAB does not read the data correct from the Oscilloscope

Question

Nikan Fakhari 2022-1-20

评论： Cristhian Zárate 2022-7-22

Hi there,

Recently I have had issues with the binblockread function in matlab.

I am trying to read a waveform from a oscilloscope, I can clearly see the waveform on matlab, however the voltage

values are printed incorrect. I am using an int8 for the precision.

I was wondering is there any scale conversion exist here that I am unware of?

I would highlty appreciate some help on this,

Thank you very much

Nikan

Hi Nikan,

Usually, in the programming manual, you have the documentation of how to read the data from the instrument.

For example:

" The read data consists of two parts - TMC header and data packet, like #900000ddddXXXX..., among

which, “dddd” reflects the length of the valid data packet in the data stream, “XXXX...” indicates the data

from the data packet, every 2 bytes forms one effective data, to be 16-bit signed integer data "

Assuming you alread read the preamble, next you read the data

adc8bit_data = binblockread(scope_obj, 'int16');

Then, you process the adc data as found in the manual...

i). the channel voltage -

channel voltage = ( channel ADC data / 6400 - channel zero offset) * channel volt scale

Note: ADC Data = waveform data, or Vmax, or Vmin, or Vavg (16-bit signed integer data)

In case you don't have any information use the following walk-around

Find the value of "factor" until you get what you see in your oscilloscope screen. You can do it so by applying a 1Vpp sine waveforme.

waveform_data = (adc8bit_data/factor - vertical_offset)*vertical_scale

It would helpfull to know the brand and model of your oscilloscope.

Cris