FAQs from Rohde & Schwarz

RTO/RTP - Zoom Windows does not show waveform data


The Zoom function does not show any waveform data at specific settings, especially at slower timebases in combination with higher sample rates, High resolution and roll mode with more channels.

The problem is gone if a lower sample rate is chosen.


In Run continuous mode, the data from the acquisition is written to the memory. After finishing the acquisition, the data will be displayed on the screen and immediately after that, the data of the next acquisition is written into the memory. If there is just memory for 1 acquisition available, the data in the memory will be overwritten. To avoid that data of two acquisitions can be mixed, the data from the previous acquisition is deleted, the moment the next acquisition is started. The deleted data is then not available e.g. for zoom anymore.

Just as an example:

The acquisition is 50MSa long. 3 channels are active, all of them in High res. In High res, each Sample uses 2 bytes. This leads to 100MB memory per channel, i.e. 300MB in total per acquisition. If there are less than 600MB memory available, there is only memory space left for 1 acquisition and the data will be immediately deleted, when the data is displayed on the screen.

To avoid this behavior with this setting, there are four possibilities:

1. Increase the memory size.
2. Choose a different decimation level than High res (while keeping the number of Samples constant)
3. Reduce the number of samples.
4. Use the single acquisition mode instead of Run/Stop. The acquisition data is kept in the memory and will not be overwritten, unless "Single" is pressed again.

The last suggestion is probably the easiest possibility.

Please note:

If the memory size is increased (Memory upgrade option) please make sure that you are using the same settings. If the setup is created again, the RTO/RTP automatically choose a higher sample rate because more memory is available and the problem may occur again.