Welding System User Manual

Chapter 2 Function Reference — AO_VWrite
NI-DAQ FRM for PC Compatibles 2-46
© National Instruments Corporation
If you set the output type to current by calling AO_Change_Parameter, the floating-point
value indicates the current in amps.
Default ranges (unipolar, internal voltage reference):
AO-2DC device: 0 to 0.02 A
VXI-AO-48XDC: 0 to 0.02047 A
Using This Function
AO_VWrite scales voltage to a binary value and then writes that value to the DAC in the
analog output channel. If the analog output channel is configured for immediate update, the
output voltage or current changes immediately. Otherwise, the output voltage or current
changes on a call to
AO_Update or the application if an external pulse.
If you have changed the output polarity for the analog output channel from the factory setting
of bipolar to unipolar, you must call
AO_Configure with this information for AO_VWrite to
correctly scale the floating-point value to the binary value.
You also can use this function to calibrate the VXI-AO-48XDC. On this device, writes to
channel number 48 affect the voltage or current offset calibration, depending on the output
type of this channel as set by the
AO_Change_Parameter function. In addition, writes to
channel number 49 affect the voltage or current gain calibration, which also depends on the
output type of the channel as set by the
AO_Change_Parameter function.