Measurement Computing UL for NI LabVIEW - Manual (Page 25)

Universal Library Virtual Instruments (VIs) Analog Input VIs
APretrFg.VI
Waits for a trigger to occur and then returns a specified number of analog samples before and after the trigger
occurred. If only 'polled gate' triggering is supported, the trigger input line (refer to the hardware user's
manual) must be at TTL low before this VI is called or a
TRIGSTATE error will occur. The trigger occurs when
the trigger condition is met. See SetTrig.VI on page 33 and board-specific information for details. This VI will
not return to your program until all of the requested data has been collected and returned to
DataArray .
Summary:
Inputs: BoardNum [U32] - The board number assigned when installed with InstaCal. Can
be 0 to 100.
LowChan [I32] - First A/D channel of scan
HighChan [I32] - Last A/D channel of scan
PretrigCount [I32] - Number of pre-trigger A/D samples to collect
TotalCount [I32] - Total number of A/D samples to collect
Rate [U32] - Sample rate in scans per second
Range [I32] - A/D range code or 0
ConvertData [TF] - Convert data option (Boolean)
DTConnect [TF] - DT connect option (Boolean)
ExtMemory [TF] - External memory option (Boolean)
Outputs: DataArray [U32] - Data array that stores A/D values
PretrigCount [I32]- Actual number of pre-trigger A/D samples collected
TotalCount [I32] - Total number of A/D samples collected
Rate [U32] - Actual sample rate in scans per second
ErrCode [I32] - Error code. See ErrMsg.VI
Arguments:
BoardNum The board number associated with a board when it was installed with InstaCal. The
specified board must have an A/D.
LowChan/HighChan The maximum allowable channel depends on which type of A/D board is being
used. For boards that have both single ended and differential inputs, the maximum
allowable channel number also depends on how the board is configured (8
channels for differential, 16 for single-ended).
PretrigCount Specifies the number of samples before the trigger that will be returned.
PretrigCount must be less than TotalCount - 512. If the trigger occurs too early,
fewer than the requested number of pre-trigger samples will be collected. In that
case a
TOOFEW error will occur. The PretrigCount will be set to indicate how many
samples were collected and the post trigger samples will still be collected.
TotalCount The total number of samples that will be collected and stored in DataArray .
TotalCount must be greater than or equal to PretrigCount + 512. If the trigger
occurs too early then fewer than the requested number of samples will be collected.
In that case, a
TOOFEW error will occur. The TotalCount will be set to indicate how
many samples were actually collected.
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