Chapter2 HardwareOverview
NI5911 User Manual 2-8 ni.com
ofrange and should be recalibrated by performing an internalcalibration.
During acquisition in flexible resolution mode, an error will be generated
ift hei nput to the ADC goes out of range for the converter. The fact that
thiscondition has occurred may no t beo bvious by inspecting the acquired
data due to the digital filtering that takes place on the acquired data.
Therefore,an erroroccurs to let you know that the dataincludes some
samples thatw ere out of the range of the converter and may be inaccurate.

External Calibration

External calibration calibrates the internal reference on the NI 5911.
The NI 5911 is already calibrated when it is shipped from the factory.
Periodically, the NI 5911 will need external calibration to remain within
the specified accuracy. For more information on calibration, contact
NationalInstruments, or visit ni.com/calibration. For actual intervals
and accuracy,r eferto A ppendix A, Specifications.
Triggering and Arming
Thereare several triggering methods for the NI 5911.The trigger can be an
analog level that is compared to the input or any of several digital inputs.
Youcan also call a software function to trigger the board. Figure 2-3shows
thedifferent trigger sources. When you use a digital signal, t hat signal must
beat a high TTL level for at least 40 ns before any triggers will be accepted.
Note The NI 5911 does not support delayed triggering.