Chapter4 HardwareOverview
©NationalInstruments Corporation 4-17 NI5102 User Manual
Random Interleaved Sampling
The NI 5102 supports Random Interleaved Sampling (RIS), a form of
Equivalent Time Sampling (ETS) which allows multiplication of the
maximumr eal-time sampling rate. The maximum interpolation factor
on the NI 5102 is 50, resulting in a maximum effective sampling rate
of1 GS/s. At this rate, the ratio of logical bins to physical bins is
approximately 1:9. The minimum RIS rate is 40 MS/s.
Toreconstruct the waveformwith RIS, you need to know the RIS OFFSET,
whichis the minimum value that the Time-to-Digital Converter (TDC) can
return, and the range of values, RIS GAIN, which is the maximum TDC
valueminus the minimum TDC value.
RIS OFFSET and RIS GAIN may varyslightly from digi tizer to digitizer.
Both thesep arameters are computed individuallyfor each digitizer at the
factoryand the values are stored in the onboard EEPROM.
UseRIS GA IN to determine the number of physical bins per logical bin for
the desired interpolation factor.You could use RIS OFFSET to start the
waveformreconstruction at the origin, but this parameter may drift over
time and temperature,which could result in an inaccurate waveform.
Note ETS and RIS work only with repetitivesignals.
Foran in-depth discussion of these concepts and how to use RIS, see
Chapter5, Tasks and Examples, in your NI-SCOPE Software User Manual.
Calibration
Calibration is the process of minimizing measurementerrors bymaking
smallcircuit adjustments. All NI 5102 digitizers come factory calibrated to
thelevels indicated in Appendix A,Specifications. However, your digitizer
needs to be periodically recalibrated in order to maintain its specified
accuracy.You have two choicesfor recalibration, internal (orself)
calibration, and external calibration. A third option, external restore,
restores the factory settings and should be used only in theevent of an
internal calibration failure.
Internalcalibration is executed with an NI-SCOPE software call or a
LabVIEW VI. It requires no external connections and adjusts only the
timing for RIS acquisitions. It should be performed upon installation of