Digital Multimeters (DMMs) and Precision DC Sources

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Configuring Advanced Sequencing

Does anyone have an implemented LabView example of the following advanced sequence?

 

Configuring Advanced Sequencing 

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There are two LabVIEW shipping examples that show how to do Advance Sequencing (NI-DCPower Advanced Sequence Changing Aperture Time VI and NI-DCPower Advanced Sequence Changing Output Function VI). Have you looked at these yet? Or, are you looking for something different?

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Hi sherlockholm,

I'm trying to understand what kind of things you can do with an advanced sequence.

I guess I'm not clear on some fundamentals when it comes to the capability of the PXIe-414x SMU's capabilities. For example:

- Are advance sequences still considered HW-timed sequences? Or are they SW-timed since they seem to involve elaborate loops and decision making?

- Can I run a HW-sequence like a voltage sweep and decide at every voltage step wether to halt or proceed to the next step? Or will that involved all the overhead and non-deterministic disadvantages of a SW-timed sequence?

The steps described in the Digital Multimeters (DMMs) and Precision DC Sources instructions seem very abstract.

 

Thanks 

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- Are advance sequences still considered HW-timed sequences? Or are they SW-timed since they seem to involve elaborate loops and decision making?

 

They are hardware timed. You can configure how to advance from one step to the next, including using hardware triggers via the PXI backplane, software triggers, or events produced within the device (Measure Complete Event, Source Complete Event, etc)

 

- Can I run a HW-sequence like a voltage sweep and decide at every voltage step wether to halt or proceed to the next step? Or will that involved all the overhead and non-deterministic disadvantages of a SW-timed sequence?

 

No, the hardware cannot do any conditional branching based on measurement data. In order to do what you describe you would need to fetch measurement data on each step and in software decide whether to send a software trigger or not in order to advance to the next step.

Marcos Kirsch
Chief Software Engineer
NI Driver Software
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Thanks Kirsch.

What about doing the same advance sequencing in CVI using the niDCPower API's.

Would that approach execute more efficiently?

 

 

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First lets get this out of the way: I don't expect using CVI will yield faster results than using LabVIEW. LabVIEW code gets compiled to machine code using clang. It's pretty darn good. And at the end of the day you are talking about doing hardware I/O and that is going to dominate your execution time.

 

I gather you are trying to "run a HW-sequence like a voltage sweep and decide at every voltage step wether to halt or proceed to the next step".

 

If this is correct, then your best bet is to use a sequence, configure the hardware so that you need to send a software trigger in order to output the voltage for the next step, and fetch after each software trigger is sent in order to decide whether to advance or not. This will have software-timed induced jitter, unfortunately. There is no way to make this be completely hardware timed as far as I know.

Marcos Kirsch
Chief Software Engineer
NI Driver Software
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Hi Marcos,

Thanks for the reply.

Do you have any examples (Labview or CVI) for the sequence approach you suggested?

Regards.

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Marcos,

Would a sequence with SW trigger as an input condition for advancing to the next step be faster than a SW loop containing Single point measurements? They seem equivalent to me.

Thanks

 

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> Would a sequence with SW trigger as an input condition for advancing to the next step be faster than a SW loop containing Single point measurements? They seem equivalent to me.

 

Yes. There is a lot happening every time you configure and generate a single point measurement. But sending a software trigger is a very lightweight operation.

Marcos Kirsch
Chief Software Engineer
NI Driver Software
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Marcos,

 

Great! Looks like sequence mode with SW trigger for advancing the step is the way to go. Would you have a CVI or LabView example you could share for this approach?

By the way, I am using the PXIe-4141 SMU.

 

Thanks!

 

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