User manual

Chapter 3 Software Overview
© National Instruments Corporation 3-19 NI-DAQ User Manual for PC Compatibles
When accurate sample timing is important, you can use external conversion
pulses with
AI_Clear
,
AI_Setup
,and
AI_Check
to sample your signal
on the analog input channels. See Figure 3-2 for the function flow typical
of single-point data acquisition using external conversion pulses. However,
this method works only if your computer is faster than the rate of
conversion pulses. Refer to the Data Acquisition Functions section later in
this chapter to learn more about interrupt and DMA-driven data acquisition
by using high-speed data acquisition.
When you are using SCXI analog input modules, use the SCXI functions
to set up the SCXI chassis and modules before using the
AI
functions
described in Figures 3-1 and 3-2.
Figure 3-2. Single-Point Analog Reading with External Conversion Timing
Ye s
No
Another reading?
AI_Clear
AI_Mux_Config
AI_Configure
AI_Check
AI_Setup
Change analog input
default configuration.
Add AMUX-64T
configuration.
Clean up onboard FIFO
memory for new conversion.
Select an analog
input channel.
Check for new data in
FIFO memory.