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Page 11 | ni.com | Multifunction I/O
Independent Timing Engines for Analog and Digital I/O
Advanced timing and triggering functionality on data acquisition devices has often relied on onboard
counters and complex signal routing to achieve specialized hardware-timed performance. NI’s
multifunction I/O technology offers completely independent sample clocks and triggers for each different
group of I/O on a multifunction device. Retriggerable acquisitions, for example, involve waiting for a
trigger condition to be met, taking a finite number of samples, and then immediately rearming the trigger
for the next acquisition. Using driver software function calls to rearm the trigger risks missing the next
trigger due to software latency; therefore, the best possible performance requires a hardware-timed
approach. In the past, counters were the only way to implement hardware-timed retriggering, and so
counters would be used to generate a retriggerable pulse train, which was then internally routed to act
as the analog input sample clock. Devices with advanced timing capabilities can perform this type of
action natively, which greatly simplifies the hardware programming and measurement configuration
process.
Self-Calibration and Two-Year Guaranteed Specifications
Self-calibration provides the ability to characterize nonlinearity, gain, and offset errors in Multifunction
I/O Devices. These changes are caused by deviations in the operating environment as well as
manufacturing variations in the integrated circuitry that may have shifted since the last external
calibration. Supported devices use an integrated self-calibration algorithm called NI-MCal to
characterize and save the correction polynomials to an onboard EEPROM, and does so in a matter of
seconds. This allows subsequent measurements to be scaled automatically by the device driver
software before being returned to the user through application software. NI-MCal has the unique ability
to return calibrated data from every channel in a scan, even if they are at different input ranges. This
means a device can easily load and apply channel-specific correction functions even while scanning at
maximum device rates without impacting performance.
By eliminating the limitations of hardware components traditionally used for device error correction and
using the power and speed of software and PC processing, NI-MCal raises the bar for measurement
accuracy by redefining device self-calibration. Most Multifunction I/O Device models have a two-year
external calibration cycle thanks to the self-calibration precision circuitry that minimizes the maintenance
burden of deployed systems, while also maintaining tight measurement tolerances. Visit ni.com to learn
more about NI’s calibration services.