DCPower software triggered measurement to buffer

[JLGuerra]

I am trying to use a PXIe-4135 SMU to perform a voltage sweep where I use software triggers to independently trigger the output voltage and current measurement on a PXIe-4135 SMU and have the data stored in the measurement record until all measurements are complete.

I have tried a variety of approaches to try to get this to work, but have not been successful. Attached is an example (NI-DCPower software trigger voltage sweep data to buffer.vi) of an approach I took. While it works and appears to complete the sweep successfully, only the last measurement is returned when I go to retrieve the data from the buffer. Screenshot below:

The second example (NI-DCPower software trigger voltage sweep data each iteration.vi) shows the working expected functionality, but with the buffer being read after each applied voltage. This is functional, but my expectation is that accessing the buffer on each iteration causes a measurable speed reduction (I was trying to test this theory).

I understand that what I am trying to accomplish can be done using hardware triggering as is shown in the NI-DCPower examples. Is there no way to use the buffer with software triggering for more than one measurement?

The ultimate application is to use two SMUs such that SMU_1 sweeps voltage and currents are measured on SMU_2 for each SMU_1 voltage, while SMU_2 also maintains an applied constant voltage. If there is a way to accomplish this using hardware triggers, I'd be interested in knowing about it, but the approach that I was able to think of revolves around using software triggers to trigger the source and measure of the SMU's independently.

Any insight or direction you can provide would be helpful.

[JLGuerra]

I reached out to the NI team for help with this issue and they were able to provide me with the answer to this question.

It turns out that the Measure Record (buffer) is only relevant when using sequence mode, not single point mode as I have done in the examples I gave. So when trying to pull data after all measurements have been taken, you only get the latest measurement taken.

The NI team also pointed out that the buffer in sequence mode is created on the PC, not on the instrument, and that the performance difference between operating in sequence mode and single point mode is negligible.

This means that, for my specific application, I won't need to specify triggering explicitly and will be able to use the Meas Multiple NI-DCPower VI.

Hopefully this is helpful to someone else as well.