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Chapter 2 Function Reference — SCXI_Set_Input_Mode
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National Instruments Corporation 2-361 NI-DAQ FRM for PC Compatibles
SCXI_Set_Input_Mode
Format
status = SCXI_Set_Input_Mode (SCXIchassisID, moduleSlot, inputMode)
Purpose
Configures the SCXI-1122 channels for two-wire mode or four-wire mode.
Parameters
Input
Parameter Discussion
inputMode is the channel configuration you want to use.
0: two-wire mode (module default).
1: four-wire mode.
Using This Function
When the SCXI-1122 is in two-wire mode (module default setting), the module is configured
for 16 differential input channels.
When the SCXI-1122 is in four-wire mode, channels 0 through 7 are configured to be
differential input channels, and channels 8 through 15 are configured to be current excitation
channels. The SCXI-1122 has a current excitation source that will switch to drive the
corresponding excitation channel 8 through 15 whenever you select an input channel 0
through 7. Channel 8 will produce the excitation when you select input channel 0, channel 9
will produce the excitation when you select input channel 1, and so on. You can use four-wire
mode for single point data acquisition, or for multiple channel scanning acquisitions. During
a multiple channel scan, the excitation channels will switch simultaneously with the input
channels.
You can hook up an RTD or thermistor to your input channel that uses the corresponding
excitation channel to drive the transducer.
You can call the
SCXI_Set_Input_Mode function to enable four-wire mode at any time
before you start the acquisition; you can call
SCXI_Set_Input_Mode again after the
acquisition to return the module to normal two-wire mode.
Name Type Description
SCXIchassisID i16 chassis ID number
moduleSlot i16 module slot number
inputMode i16 channel input mode configuration