Capturing Data from RS232, Tektronix TDS210

[coldfiremc]

Hi all, this is my first post

I have an old Tek TDS210 oscilloscope in my hands. I want to log some waveforms and make some "more decent" graphs, so made one of those null modem cables, and I managed to get data almost successfully with matlab... there are some quirks; the first: Apparently Data is referred to -32768,+32768, and it hasn't the real voltage and time values. Of course, I can get Volts per division and time base, and other properties from the serial interface, but I don't know how to calculate the correct values for waveform. How I can calculate them? Is this the normal behavior? I remember that a TDS1001B with VISA over usb, delivered data in the final representation almost inmediately, so I can expect the same of the first? The second problem: by a strange reason, TekVISA doesn´t work properly from matlab it loops the query command infinetely, and cant get anything, however it says that this TDS210 works with that protocol.
I haven't buy this scope, so don't cry that "there are better new scopes", I know it.

I will attach you a .csv file and a plot so you can check data. Is the first channel connected to probe test clamp.

thanks for your help 

[Nitrousoxide]

From a quick glance, 15 bits of data will give you a maximum unsigned value of 32768. The data is probably in signed 16-bit form from just a guess.
Obviously, the scope doesn't have 16 bits of resolution, so at a guess, the values might be scaled by a factor of 256x (not too sure). To convert that into a meaningful form, you'd need the ADC maximum input per range.

As for timebase, if you have the sample time you then know the time between each sample.

I am confused as to what specifically you would like to calculate? Are you referring to measurements that can be performed by the scope, such as period, Vrms etc? There are quite a few matlab commands that allow you to perform those.

Another tip is to check out the test equipment interface toolbox command: oscilloscope();
What you may need to be careful of, especially with some scopes and Matlab is that they don't transfer the full sample memory, (i.e. Rigol has a maximum size of 1200 points) and thus may be downsampled.

[coldfiremc]

thx man.

I managed to get correct values with 1v per div. I divided all values by 65535. however this "stops to work" when I shift the position with the vertical knobs or if I change scale. Also I managed to use VISA. The problem was incorrect serial port settings.
The Instrument control toolbox is transferring 2500 samples to PC. Looks enough . Is quite slow... Is GPIB an "upgrade" option here? I have an old gpib pci card, but i can't make it work under modern windows or linux versions it just says IEE488.2.

I want to graph the data to make reports, and also logging, also measure RMS, frequency, put cursors to calculate time or voltage offsets.

[Nitrousoxide]

I want to graph the data to make reports, and also logging, also measure RMS, frequency, put cursors to calculate time or voltage offsets.

For reports, write all your code in a script file and then click on the publish tab, it will give many options to generate a nice report.
Again, with a script you can loop the readWaveform/getWaveform function.

For RMS values, you can just execute: rms(data)

For finding the frequency, there's no specific function to find a "trigger". So there are two ways to find the frequency: Write your own code to find the zero crossings, however this will usually fail as is the data is non-periodic or contains more than a single tone, the reported frequency may not be accurate. Second option would be to utilise the fft and findpeaks function (which I would recommend using).

As for using cursors, there are some available in the plot window. It is the 10th icon in the plot toolbar, named "Data Cursor".


I can't make a comment on how fast GPIB is as I have never used it. (Only used LXI ).

When you change scale, you need to divide by a different value.