Measurement Computing UL for NI LabVIEW User Manual
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Universal Library Virtual Instruments (VIs)
Analog Output VIs
Continuous
This option (True) can only be used with boards which support interrupt, DMA or
REP-INSW transfer methods. This option puts the VI in an endless loop. After it
outputs the specified (by Count) number of D/A values, it resets to the start of
DataArray and begins again. The only way to stop this operation is with
StopBg.VI.
Simultaneous
When this option is set (True) (if the board supports it and the appropriate switches
are set on the board) all of the D/A voltages will be updated simultaneously when
the last D/A in the scan is updated. This generally means that all the D/A values
will be written to the board, then a read of a D/A address causes all D/As to be
updated with new values simultaneously.
ExtClock
If this option (True) is used then conversions will be paced by the signal on the
external clock input line rather than by the internal pacer clock. Each conversion
will be triggered on the appropriate edge of the external clock input signal (refer to
the board-specific information). When this option is used the
Rate
argument is
ignored. The sampling rate is dependent on the trigger signal.
Options
for the board
will default to transfer types that allow the maximum conversion rate to be attained
unless otherwise specified.
Range
If the selected D/A board does not have a programmable range feature, this will be
ignored. Otherwise the gain can be set to any of the ranges that are supported by
the selected D/A board. See the "
" table on page 19 for valid
values. Refer to board-specific information contained in the Universal Library
User's Guide (available on
he list of ranges supported by each board.
Rate
(output)
Actual sampling rate in channel scans per second. This may be different from the
requested rate because of pacer limitations.
ErrCode
Error code returned from the Universal Library. Zero if no error occurred. Use the
ErrMsg VI to convert
ErrCode
into a readable string.
Context
Data structure containing information from a background operation. Some of the
information included is the board number, the data array, the array size, and the
initial status of the background operation.
Follow the steps below when wiring this VI:
1.
Start a background operation.
2.
GetStatus.VI checks for completion (boolean output called "Running").
3.
StopBg.VI terminates the operation, if not already done, and frees memory aliases.
4.
Data output from the background operation is passed to GetStatus.VI and StopBg.VI
via "Context", and can be wired from one or both of them for intermediate or final
actions, respectively.
The demo VIs illustrate this process effectively.
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