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Keysight SBE In-Depth – Ch7: Keysight BenchVue Test Flow Automation

Gough Lui
Keysight SBE In-Depth – Ch7: Keysight BenchVue Test Flow Automation

In this section, I will explore the state of Test Flow automation as it presently stands with regards to the Smart Bench Essentials Kit.

Is Test Flow Still Alive?

When I proposed my review, I was very excited to have the potential to try out the Test Flow automation tool, as it was to provide a code-free, block-based programming environment that would be intuitive and ideal for students who may not be otherwise versed in the technicalities of SCPI commands.

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When I did a quick search for Test Flow, I found that the app was somehow Obsolete. But this was merely a false alarm – apparently, this is because Test Flow was previously a separately licensed feature but has now become freely available to use within Keysight BenchVue Platform. As a result, there is no longer a need for this separate app and license and Keysight are still big on the potential of Test Flow.

PathWave BenchVue to Test Flow?

Unfortunately, this is where the flow hits an abrupt wall, because of a technicality. With the Smart Bench Essentials which is supported only by PathWave BenchVue Individual Apps, at this time, Test Flow is an app within the older Keysight BenchVue Platform. As a result, at this time, there is no connection or new version of Test Flow that would work with the Individual Apps, however, this is apparently in the works.

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Evidence of this can be seen in the Power Supply 2021.2 app, which if you click on the person icon next to the minimise icon, you can choose to preview features which leads to this box that allows for enabling integration.

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Unfortunately, despite updating my Keysight BenchVue Platform to the latest version as of review publication, the software was unable to detect and integrate with the platform to access Test Flow features.

Keysight BenchVue Test Flow … The Manual Way!

This leaves us to working with Test Flow in a manual way, as you would if working with unsupported or non-Keysight instruments. This necessitates looking up SCPI commands and building up your flow using the SCPI block which requires (tediously) setting the instrument address and command for each block.

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I first started by building up a flow to run an I-V curve on just the power supply. The process was relatively intuitive assuming familiarity with SCPI commands and I appreciated the ability to view the plot being built as the test flow proceeds, as well as the ability to single-step the program for debugging purposes. Unfortunately, the plotting is still relatively limited, without the ability to easily change the scale, but serves the purpose of visualising trends as the flow is run.

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The visual effect of highlighting the current block being executed makes the program easy to understand, while the collected data is stored in .hdf5 files and can be easily exported to other formats. Blocks can have their colours changed to allow for easier interpretation of results.

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I feel that Test Flow has a lot of positives – it’s definitely easy to use and intuitive to grasp, with excellent user feedback. Compared to LabVIEW, it’s definitely less clunky and chunky, but it doesn’t exactly make things easy when mixing-and-matching instruments. Unfortunately, because of the lack of Smart Bench Essentials instrument integration at the present time, the use of SCPI blocks makes programming more tedious than it needs to be. I found it more time-efficient to eschew Test Flow for a direct pyvisa approach for more complicated work, especially because the performance of Test Flow is also somewhat limited owing to continuous error checking routines.

Experiment: I-V Curve of an LED with Two Instruments

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In this test, I decided to use the power supply to do an I-V sweep of an LED, however, measuring the current based on the power supply and the DMM for a more accurate view.

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The data from the power supply shows some granularity and offsets, especially in the low current regime.

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The data from the DMM is more accurate, however, for a plot of this scale, it’s hard to visually tell the difference. However, it does illustrate that Test Flow easily handles experiments across more than one instrument even if it means resorting to old-fashioned SCPI commands to control the instruments. It reminds us that we are working with real test equipment that implement SCPI-standard commands which is good experience to have.

Conclusion

It is unfortunate, given my enthusiasm and the critical role that Test Flow plays in integrating the multiple instruments to perform more sophisticated tasks, that the new PathWave BenchVue Individual Apps are not yet ready to integrate with Test Flow. While Keysight seems committed to bringing this integration, it seems to be working towards integrating Test Flow connectivity which will require the older Keysight BenchVue Platform to also be installed alongside to provide Test Flow. Whether this will remain the case in the future is unknown, but is not an optimal situation, as it means even more bandwidth and disk space consumption.

It seems that the Power Supply 2021.2 app already has a preview integration with Test Flow, however, I was not able to get it to detect my Keysight BenchVue Platform installation despite it being up-to-date. As a result, I had to resort to using Test Flow manually, as if working with an unsupported/non-Keysight instrument. This requires using SCPI blocks with manually selected address and manually entered commands. This is a tedious process which would be avoided if the integration were working correctly.

However, when it was all done, Test Flow is very nice to use. It is intuitive in the way it displays the program flow blocks, highlights execution as it proceeds, live-plots results alongside while recording them for later export and allows for single-stepping for debugging of flows. The solution is a lot easier to use and seems lighter than LabVIEW, although it still mainly plays well only with Keysight supported equipment. The use of SCPI blocks is sub-optimal, but does allow users to practice with using SCPI – after all, these instruments are real pieces of test equipment and this could serve to aid the migration to code-based automation (such as pyvisa which I have extensively used for more serious tasks). Running multiple instruments is no challenge and the ability to colour code blocks makes data interpreting easier, however, I did find the plotting function to still be somewhat limited in terms of zooming and rescaling the plot.

I feel that for the bench to be truly “smart”, it must have some automation capability as the BenchVue apps on their own are little more than another remote front-panel with ability to configure settings and log data. When Test Flow is involved, you can start to involve multiple instruments and run sequences which make decisions based on the measured data. As a result, I feel it is unfortunate that Test Flow integration with the Smart Bench Essentials is still a work-in-progress as the package is not only the hardware but also the supporting software.

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This post is part of the Keysight Smart Bench Essentials RoadTest Review.

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  • in reply to Gough Lui

    Good points.

    When I saw the possibility for setting up an automated testing system, I became very interested.

    I helped define a number of these types of integrated testing systems in the past and have some applications where I could use that type of capability, if it wass easy to use and off the shelf.

    From your review I can see the potential, but the implementation is probably too immature to consider for now.

  • in reply to DAB

    Again, an excellent question .

    My opinion, generally speaking, is that time-to-market seems to be a key parameter that many test and measurement companies are chasing. After all, this may mean the difference between sales or no sales in a market where consumers may be buying a given product every four-or-so years. Because of this, many vendors seem to put their emphasis on the hardware and less so on the firmware and software as that can be "patched later". This results in products being supported by software or firmware which may be missing their full potential initially, but may eventually evolve to be a stable and mature platform over time.

    While I feel that this is not ideal and it is my philosophy that we should not be buying test instruments on "promises" of a better future, it is unfortunately the way things are owing to the competitive nature of the market. I've seen this trend across all major instrument vendors, so it's really hard to point any fingers, but sometimes fixes can take a long time materialise in part because of the long development and test cycle to ensure that any changes they make do not break existing use cases. However, frequent updates for instruments which are intended to be used for test and measurement purposes does raise issues regarding trust, as regressions do occasionally slip by and changes in functionality may, at times, change the results too. I would prefer if test and measurement products didn't follow the modern "agile" methodology to their development, but the market seems to dictate a preference for "new and shiny", so this is what we are left with.

    In this case, I have it on good authority that the TestFlow integration is already in the works since the kit was sent out, but isn't ready for use just yet. However, as this is during the preview period, perhaps you will revisit to see Chapter 6 where I talk about the PathWave BenchVue apps which is what most people would be likely to use on their bench for now.

    - Gough

  • Nice post.

    I too am surprised that the software is a work in progress.

    You would think that integrating your test equipment for a wide range of applications would be a high priority.

    Why build smart test equipment if you cannot exploit it in a variety of ways?

    I suspect that the manufacturer wants to tie you into only its equipment to discourage people from using other manufacturer and legacy test equipment.

    Sad that they are still playing these types of games.

    Hewlett Packard had a much more robust software package for its equipment forty years ago.