Справочник Пользователя для National Instruments Welding System 321645c-01

Chapter 2

Function Reference — AI_VRead

NI-DAQ FRM for PC Compatibles

2-18

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 National Instruments Corporation

voltage is the floating-point variable in which NI-DAQ returns the measured voltage, scaled 
to units of volts.

AI_VRead

 addresses the specified analog input channel, changes the input gain to the 

specified gain setting, and initiates an A/D conversion. 

AI_VRead

 waits for the conversion to 

complete and then scales and returns the result. If the conversion does not complete within a 
reasonable time, the call to 

AI_VRead

 is said to have timed out and NI-DAQ returns the 

timeOutError code.

When you use SCXI as a front end for analog input to an MIO or AI device, Lab-PC+, 
Lab-PC-1200, Lab-PC-1200AI, PCI-1200, LPM device, or DAQCard-700, it is not advisable 
to use the 

AI_VRead

 function because that function does not take into account the gain of the 

SCXI module when scaling the data. Use the 

AI_Read

 function to get unscaled data, and then 

call the 

SCXI_Scale

 function.

When you have an SC-2040 accessory connected to an E Series device, this function takes 
both the onboard gains and the gains on SC-2040 into account while scaling the data. When 
you have an SC-2043-SG accessory connected to your DAQ device, this function takes both 
the onboard gains and the SC-2043-SG fixed gain of 10 into account while scaling the data.

When you have any SCC accessories connected to an E Series device, this function takes both 
the onboard gains and the SCC gains into account while scaling the data.