National Instruments Welding System 321645c-01 Manual De Usuario

Chapter 2

Function Reference — DAQ_Monitor

NI-DAQ FRM for PC Compatibles

2-128

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 National Instruments Corporation

DAQ_Monitor

 is intended to return small blocks of data from a background acquisition 

operation. This is especially useful when you have put the acquisition in a circular mode 
by enabling either the double-buffered or pretrigger modes. The operation is not disturbed; 
NI-DAQ only reads data from the buffer being used by the acquisition. If the amount of data 
requested is not yet available, 

DAQ_Monitor

 returns the appropriate error code. Possible uses 

for 

DAQ_Monitor

 include deciding when to halt an acquisition based on a level, slope, or 

peak. If you are using 

DAQ_Monitor

 to retrieve sequential data (during a circular acquisition) 

and NI-DAQ overwrites a block of data before it can copy the data, NI-DAQ returns an 
overWriteError warning. 

DAQ_Monitor

 then restarts sequential retrieval with the most 

recently acquired block of data.

If NI-DAQ overwrites a block of data as it is copied to monitorBuffer, NI-DAQ returns the 
overWriteError error. The data in monitorBuffer might be corrupted if NI-DAQ returns this 
error.