National Instruments DAQ M Series - Manual (Page 42)

Chapter 4 Analog Input
NI 6236 User Manual 4-18 ni.com
With NI-DAQmx, the driver will choose the fastest conversion rate possible
based on the speed of the A/D converter and add 10 µs of padding between
each channel to allow for adequate settling time. This scheme enables the
channels to approximate simultaneous sampling and still allow for
adequate settling time. If the AI Sample Clock rate is too fast to allow for
this 10 µs of padding, NI-DAQmx will choose the conversion rate so that
the AI Convert Clock pulses are evenly spaced throughout the sample.
To explicitly specify the conversion rate, use the AI Convert Clock Rate
DAQmx Timing property node or function.
Caution Setting the conversion rate higher than the maximum rate specified for your
device will result in errors.
Using an Internal Source
One of the following internal signals can drive ai/ConvertClock:
• AI Convert Clock Timebase (divided down)
• Counter n Internal Output
A programmable internal counter divides down the AI Convert Clock
Timebase to generate ai/ConvertClock. The counter is started by
ai/SampleClock and continues to count down to zero, produces an
ai/ConvertClock, reloads itself, and repeats the process until the sample is
finished. It then reloads itself in preparation for the next ai/SampleClock
pulse.
Using an External Source
Use one of the following external signals as the source of ai/ConvertClock:
• Input PFI <0..5>
• RTSI <0..7>
• PXI_STAR
Note Refer to the NI 6236 Specifications for the minimum allowable pulse width and the
propagation delay of PFI <0..5>.
Routing AI Convert Clock Signal to an Output
Terminal
You can route ai/ConvertClock (as an active low signal) out to any output
PFI <6..9> or RTSI <0..7> terminal.