As the world grows more digital, increasingly advanced communications interfaces have been instituted in PI nanopositioning and micropositioning controllers and many other instruments. Even the new E-709 compact, cost-optimized digital nanopositioning controller comes complete with an SPI interface for command communications at the servo update rate of the controller (in addition to standard USB and RS-232 interfaces and a wealth of TTL trigger and synchronization lines). We discussed some of the newest novel interfaces and their applications in the presentation linked in our earlier blog post, Gleanings from SMB 2011.
But it's important not to overlook the benefits of the original fast, deterministic, real-time interface: analog. Most of our nanopositioning controllers are equipped with analog interfaces for position or autofocus command input, plus a feedback sensor monitor output (for closed-loop units). Even our current-generation digital nanopositioning controllers feature analog I/O options across-the-board.
There are many compelling advantages to analog interfacing:
- Generating analog position steps and waveforms is very easy with today's software tools and powerful multifunction analog I/O hardware for personal computers.
- The most popular analog I/O products, from National Instruments, share a common software interface between models. So software written for one model will work on other models and is readily transportable across operating systems.
- Highly synchronous multichannel I/O is readily achieved in any of the popular programming languages, meaning nanopositioning processes can be performed in parallel with process metrology-- essential for improving throughput in scanning and other high-dynamic processes.
As to hardware, this link will open a window to a National Instruments product selector page that presents a wide variety of analog multifunction devices suitable for most nanopositioning applications. The following criteria were used:
- At least one analog input for process metrology or sensor acquisition
- At least one analog output for commanding the position of open- or closed-loop nanopositioners
- Waveform output capability (versus static-only updates for some other models.
- Compatibility with the NI-DAQmx driver, the gold standard for analog I/O programming in any language.
Additional selectors are available to tailor the selection to your application needs and budget.
Although we can of course only test our Analog GCS LabVIEW library with a subset of NI's extremely broad offering, all the devices shown should work since all work with the NI-DAQmx driver.
If your budget allows, our top recommendation of all the current NI offerings is the top-of-the-line USB-6259 BNC (see photo). This is a portable, self-contained USB unit capable of astonishing throughput and microsecond-scale synchronization-- performance that frankly took us aback when we first used it, as we expected the USB interface would be a bottleneck. It has since been our recommendation for our CyberAligner high-throughput modular alignment engine since it also allows the workstation to be run from a laptop or virtual machine. It offers sixteen 16-bit differential analog inputs with an acquisition rate of 1.25 mega-samples/sec and four 16-bit analog outputs with a blistering update rate of 2.8 mega-updates/sec. That fast analog output speed makes it the ultimate choice for enhanced-resolution HyperBit applications, and we have achieved 27 bit positioning resolution using this unit. Its integrated BNC connectors are convenient and eliminate having to purchase a cable and BNC box.
Of course, all that functionality may be overkill for your application and budget. Fortunately there are plenty of other models with different form factors, fewer I/O options, different resolution, and more moderate speeds. There is even an unpackaged OEM version of the USB-6259.
There's lots of life left in analog, a venerable and truly real-time interface.
Read these papers for the latest on high-througput digital interfacing.
Although we can of course only test our Analog GCS LabVIEW library with a subset of NI's extremely broad offering, all the devices shown should work since all work with the NI-DAQmx driver.
If your budget allows, our top recommendation of all the current NI offerings is the top-of-the-line USB-6259 BNC (see photo). This is a portable, self-contained USB unit capable of astonishing throughput and microsecond-scale synchronization-- performance that frankly took us aback when we first used it, as we expected the USB interface would be a bottleneck. It has since been our recommendation for our CyberAligner high-throughput modular alignment engine since it also allows the workstation to be run from a laptop or virtual machine. It offers sixteen 16-bit differential analog inputs with an acquisition rate of 1.25 mega-samples/sec and four 16-bit analog outputs with a blistering update rate of 2.8 mega-updates/sec. That fast analog output speed makes it the ultimate choice for enhanced-resolution HyperBit applications, and we have achieved 27 bit positioning resolution using this unit. Its integrated BNC connectors are convenient and eliminate having to purchase a cable and BNC box.
Of course, all that functionality may be overkill for your application and budget. Fortunately there are plenty of other models with different form factors, fewer I/O options, different resolution, and more moderate speeds. There is even an unpackaged OEM version of the USB-6259.
There's lots of life left in analog, a venerable and truly real-time interface.
Read these papers for the latest on high-througput digital interfacing.
- Interfacing Fast Nanopositioners to Track-Following Servos
- High-speed, low latency communications for nanopositioning in Single-Molecule Biophysics
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