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AI Convert Clock Signal
Caution
Setting the conversion rate higher than the maximum rate specified for your
device will result in errors.
© National Instruments Corporation
You can use the AI Convert Clock (ai/ConvertClock) signal to initiate a
single A/D conversion on a single channel. A sample (controlled by the
AI Sample Clock) consists of one or more conversions.
You specify either an internal or external signal as the source of
ai/ConvertClock. You also specify whether the measurement sample begins
on the rising edge or falling edge of the ai/ConvertClock signal.
By default, NI-DAQmx will choose a conversion rate so the pulses are
evenly spaced throughout the sample. This allows for the maximum settling
time between conversions. To approximate simultaneous sampling, you can
manually increase the conversion rate. By default, Traditional NI-DAQ
(Legacy) chooses the fastest conversion rate possible for the device with
10 µs of delay added between each conversion to allow the channel to some
time settle.
Using an Internal Source
One of the following internal signals can drive ai/ConvertClock:
•
CTR 0 OUT (the output of Counter 0)
•
AI Convert Clock Timebase (divided down)
The AI Convert Clock Timebase is driven by either the AI Sample Clock
Timebase or the Master Timebase. A programmable internal counter then
divides down the AI Convert Clock Timebase to generate ai/ConvertClock.
The counter is started by the ai/SampleClock signal and continues to count
down and reload itself until the sample is finished. It then reloads itself in
preparation for the next ai/SampleClock pulse.
Several other internal signals can be routed to convert clock timebase
through RTSI. Refer to Device Routing in MAX in the NI-DAQmx Help or
the LabVIEW 8.x Help for more information.
2-41
Chapter 2
Analog Input
E Series User Manual
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