SMU 4141 sequence length too long

[JaredRo]

Hi Karl,

The PXI-4132 supports sequence streaming, allowing you to output a sequence of virtually any length.  This feature has not yet been added for 414x devices, however.  

The actions suggested above are the best way to resolve the error.

Good luck with your application!

[KarlJason]

Hi Jared,

Thanks for the reply.

This is very unfortunate.  I specifically bought the 4143 for this purpose.

Would you know if this is specified on the datasheet or specifications?

I think these features shoudl be specified on these documents.

Best Regards,

Karl

[JaredRo]

Sorry for the delay in my response to you.

The maximum sequence length is not explicitly listed in the specifications document or the data sheet for the 4143 device.  This is in part because the maxmimum sequence length can vary depending on the contents of the sequence. 

It is a good idea to have information about the maximum sequence length stated in the documentation, though.  I will file a request to have a typical specification listed for the maximum sequence length added to the specifications document.

[JaredRo]

UPDATE:
Sequence streaming is now available on all NI PXIe-414x devices in addition to the NI 4132 & the NI 4135/6/7/8/9.  As of this posting, the most recent version of the driver is NI-DCPower 15.1 and can be found here.

[TommyWoj]

I'm looking for a control or property node that will configure a PXIe-4140 to output an arbitrary sequence at the maximum spec output update rate of 100ks/s.

I would have expected that the instrument would output data at its maximum spec rate as default operation with the user/programmer/engineer required to add appropriate source delay values to generate lower frequency arbitrary signals, but this seems to be not the case.

I tried setting transient response to "Fast" and source delay to 0, but the max update rate I'm measuring with a scope is 60 samples/s.  Increasing source delay decreases the effective update rate, but with zero delay the update rate is nowhere near 100ks/s.

What am I missing?  Drivers too old (NIDCPWR1.9)?

[Jake_H]

I would reference this forum post on how to configure the SMU in sequence mode and output a waveform. The post includes some reference code. 

I also recommend upgrading your driver to the latest version. You will have a limitation on the number of sequence setpoints if you continue using DCPower 1.9.

[lfbsvsfbsapruwiq890]

Is there a special command required to use sequence streaming (as opposed to regular sequences)? I have a brand new PXIe-4144 and the latest driver, but the longest sequence I could fit before raising a sequence length error was ~ 500 points. I use the Python API. I found no special command in the documentation. Maybe the Python API does not support streaming?

[kirsch]

The Python API calls into the same driver runtime as the C, .NET, LabVIEW APIs.

From a client's perspective, there is no difference in how you program the instrument in order to stream the instructions. This was done as an under-the-hood change to the driver.

I am not sure what the status of this is specifically for the PXIe-4144.

[lfbsvsfbsapruwiq890]

Good to know that the Python API has the same capabilities.

Turns out that I most likely confused the SMUs I had connected to the chassis. I can reproduce the “sequence too long” error with PXIe-4154, but not with the PXIe-4144. It works fine with a sequence of 30,000 elements (longest I have tested so far). The readout takes about 20 ms per element, so it takes a while. It’s not perfect, but I can live with it. I assume I cannot start the next sequence while the previous is still being read out?

[kirsch]

> The readout takes about 20 ms per element, so it takes a while.

Meaning that you can fetch at only 20 ms per measurement?

Is your instrument configured to measure automatically after source complete?

What is the aperture time?

What is the source delay?

Are they adequate for your application?

The actual data movement is much much faster, assuming the data arrived to the host and can be fetched.