
AppendixB DigitizerBasics
©NationalInstruments Corporation B-7 NI5911 User Manual
Forexample, consider the maximum interpolation factor to be 5. If the TDC
could outputvalues from 0 to 15, then each logical bin will contain three
physicalbins, as shown in Figure B-6.
FigureB-6. Relationshipbetween Interpolation Factor,Logical Bins, and Physical Bins
Making Accurate MeasurementsForaccurate measurements, you should use the right settings when
acquiring data with your NI 5911. Knowing the characteristics of the
signalin consideration helps you to choose the correct settings. Such
characteristicsinclude:
•Peak-to-peakvalue—This parameter, in units of volts, reflects the
maximum change in signal voltage. If V is the signal voltage at any
giventime, then V pk-to-pk =Vmax –Vmin. The peak-to-peak value
affectsthe vertical sensitivity or gain of the input amplifier. If you
do not knowthe peak-to-peak value, start with the smallest gain
(maximuminput range) and increase it until the waveform is digitized
usingthe ma ximum dynamic range without clipping the signal. Refer
to Appendix A, Specifications, for the maximum input voltage for
your NI 5911 device.Figure B-7 shows that a gain of 5 is the best
setting to digitize a 300 mV,1 MHz sine wave without clipping the
signal.
PhysicalBin
3Physical Bins = 1 Logical Bin
DesiredInterpolation Factor = 5
MaxInterpolation Factor = 15
Sample
Clock
LogicalBin