ADLINK PXI-2502 - Manual (Page 29)

Operation Theorem
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Acquisition_in_progress
Scan_start
AD_conversion
Scan_in_progress
3 Scans, 4 Samples per scan
(PSC_Counter=3)
Sampling Interval t=
SI2_COUNTER/TimeBase Scan Interval T=
SI_COUNTER/TimeBase
Ch0
Ch1
C h2
Ch3
Ch0
C h1
Ch2
Ch3
C h0
Ch1
C h2
C h3
(Scan acquisition is performed in ascending sequence for enabled channels)
Trigger
Figure 4.1.1 Timing for Scan
NOTE:
1. The maximum A/D sampling rate is 400KHz for DAQ/PXI-2500 series
therefore the minimum setting of SI2_counter is 100.
2. The Scan Interval can not be smaller than the interval of data Sampling
Interval multiple by the Number of channels per Scan, i.e.: SI_counter
>= SI2_counter * NumChan_Counter
4.1.3.2 Trigger Mode
Post-Trigger Acquisition
Use post-trigger acquisition when users want to perform scans right after a
trigger signal. The number of scans to be performed after the trigger signal
is specified by the PSC_counter, as illustrated in Figure 4.1.2. The total
acquired data length =
(number_of_channels_enabled_for
_scan_acquisition) * PSC_counter.
Delay Trigger Acquisition
Use delay trigger when users want to delay the scan after a trigger signal.
The delay time is determined by the Delay_counter, as shown in Figure
4.1.3.
The counter counts down on the rising edges of Delay_counter clock
source after the trigger signal. When the count reaches 0, DAQ/PXI-2500
SERIES starts to perform the scan. The acquired data length = (num-
ber_of_channels_enabled_for_scan_acquisition) * PSC_counter. The
Delay_counter clock source can be software selected from Internal 40MHz