National Instruments SCXI-1121 - Manual (Page 96)

Chapter 5 Programming
© National Instruments Corporation 5-5 SCXI-1121 User Manual
To measure one of the four differential input channels to the SCXI-1121,
perform the following steps:
1. Write the binary pattern 000XXXCC XX000000 to the SCXI-1121
Configuration Register.
2. Measure the voltage with the data acquisition board.
To shunt calibrate one of the four differential input channels, perform the
following steps:
1. Write the binary pattern 001XXXCC XX00000 to the SCXI-1121
Configuration Register. Insert a delay of at least 1 sec if you have set
the 4 Hz filter, or at least 1 msec if you have set the 10 kHz filter. This
delay permits the SCXI-1121 amplifier to settle.
2. Measure the voltage with the data acquisition board.
To measure the voltage on the MTEMP line, perform the following steps:
1. Write the binary pattern 000XXXXX XX100000 to the SCXI-1121
Configuration Register.
2. Measure the voltage with the data acquisition board.
Indirect Measurements
Indirect measurements involve one module sending a signal to Analog
Bus 0, where it is picked up by another module and transmitted to the data
acquisition board.
Measurements from Other Modules
To perform measurements from other modules, you must cable the
SCXI-1121 rear signal connector to a data acquisition board. See
Chapter 2,
Configuration and Installation , for more information. To make
a measurement from another module, perform the following steps:
1. Perform any necessary programming to ensure that no modules are
driving Analog Bus 0. For an SCXI-1121, clearing AB0EN in the
Configuration Register will ensure that its output is not driving AB0.
2. Write the binary pattern 000XXXXX XX100011 to the SCXI-1121
Configuration Register. This step disables the SCXI-1121 from driving
Analog Bus 0 and allows Analog Bus 0 to drive MCH0 through the
output buffer.
3. Program the other module to drive Analog Bus 0 with the signal to be
measured.
4. Measure the voltage with the data acquisition board.