making a realtime waveform from TDS 420A

[AxE]

but the waveform update not really in real time,
about 0.5 - 1 second slower.
and when the time division in oscillescope increase,
it update even slower, although the oscillescope display is moving

i suspect the byte count in visa read and the "STAR\s1;STOP\s50000" will also affect the speed,
sometime the stop point lower will be faster, sometime stop point higher will be faster, depend on the time division

i attach the waveform reading VI
i communicate with the TDS 420A using GPIB

[AxE]

the byte count and point to be read will not affect the speed(tested),
and the size of the program also will not affect the speed(tested).
so what could it be?

[JLS]

Hello,

It seems like you are having problems with the transfer of the data over GPIB and corresponding update in LabVIEW. The latency you are experiencing could be in the instrument, which has to write the data to its write buffer before the data is sent. Of course there is the transfer time and the read and UI update time, but I imagine the instrument latency is playing a role here. How much data are you getting from your instrument?

Get back with some details about what and how much data you are expecting to receive if you still have questions!

Regards,

JLS

[AxE]

Hello,

I trying to get real time data from the oscilloscope and display
if the record length set to 500 points in 10 divisions
the entire recorded waveform will be 500 points, each point is 2 bytes, so there will be 1000 points + 13 headers bytes

I think TDS 420A itself can't do the job of doing real-time

[JLS]

Hello AxE,

In the literal sense, you will not get realtime data for at least the following reasons:

1. The TDS will need to transfer that data to the output buffer in order send it; this takes time.

2. GPIB handshaking is inherent in the transfer of every byte; this takes time.

Most likely the bottleneck is in the TDS, however, such a specification may exist and be documented for the TDS in the user manual.

Don't be shy if you feel I can be of any further help!

JLS

[AxE]

Hello JLS,

Thanks for your answer =]

After so many testing, i already know that the oscilloscope is unable to do realtime =[
and it does not acquire waveform when it send...
that why there is data loss while it send....
but nevermind, i don't think i can do anything about it, unless i can change to a realtime scope

[JLS]

I see, sorry to hear that and good luck with your application. Don't be shy about posting gain if you have other questions we out here can help with!

Thanks,

JLS