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Chapter 4 Analog Input
© National Instruments Corporation 4-19 NI 6232/6233 User Manual
• Use individually shielded, twisted-pair wires to connect AI signals to
the device. With this type of wire, the signals attached to the positive
and negative input channels are twisted together and then covered with
a shield. You then connect this shield only at one point to the signal
source ground. This kind of connection is required for signals traveling
through areas with large magnetic fields or high electromagnetic
interference.
Refer to the NI Developer Zone document, Field Wiring and Noise
Considerations for Analog Signals, for more information. To access this
document, go to
ni.com/info and enter the info code rdfwn3.
Analog Input Timing Signals
In order to provide all of the timing functionality described throughout this
section, NI 6232/6233 devices have a flexible timing engine. Figure 4-7
summarizes all of the timing options provided by the analog input timing
engine. Also refer to the Clock Routing section of Chapter 10, Digital
Routing and Clock Generation.
Figure 4-7. Analog Input Timing Options
M Series devices use ai/SampleClock and ai/ConvertClock to perform
interval sampling. As Figure 4-8 shows, ai/SampleClock controls the
sample period, which is determined by the following equation:
PFI, RTSI
PXI_STAR
20 MHz Timebase
100 kHz Timebase
PXI_CLK10
Programmable
Clock
Divider
ai/Sample
Clock
Timebase
ai/Convert
Clock
Timebase
PFI, RTSI
PXI_STAR
Ctr
n
Internal Output
SW Pulse
PFI, RTSI
PXI_STAR
Ctr
n
Internal Output
ai/Convert
Clock
ai/Sample
Clock
Programmable
Clock
Divider