Programming instructions

Chapter 14 SCXI Hardware
DAQ Hardware Overview Guide 14-10 www.ni.com
also has an amplifier with a fixed gain of 100. The amplification and
filtering occur before multiplexing.
SCXI-1120, SCXI-1120D, and SCXI-1121
The SCXI-1120, SCXI-1120D, and SCXI-1121 are 8-channel and
4-channel isolation modules, respectively. The input voltage range on all
three modules is ±5 V. The modules have a hardware-selectable gain on
each input channel with values of 1, 2, 5, 10, 20, 50, 100, 200, 250, 500,
1,000, and 2,000 for the SCXI-1120 and SCXI-1121. The
hardware-selectable gain on each input channel for the SCXI-1120D have
values of 0.5, 1, 2.5, 5, 10, 25, 50, 100, 250, 500, 1000. The gain fields in
Measurement & Automation Explorer are not used by NI-DAQ; those
fields are used only by LabVIEW. You use the
SCXI_Scale function to
compensate for SCXI-1120, SCXI-1120D, and SCXI-1121 gains. The
SCXI-1121 also has four excitation channels that you can use for voltage
or current excitation.
The SCXI-1305 AC/DC coupling BNC terminal block works
with the SCXI-1120, SCXI-1120D, SCXI-1121, SCXI-1140, SCXI-1141,
SCXI-1142, and SCXI-1143. The maximum common-mode voltage is
limited to 42 V
peak
or DC with the SCXI-1120, SCXI-1120D, and
SCXI-1121.
The SCXI-1320 and SCXI-1328 terminal blocks that you can use with the
SCXI-1120, SCXI-1120D, and SCXI-1121 modules each have an onboard
temperature sensor that is jumper-configurable to be either multiplexed
with the other input channels in multiplexed mode (MTEMP
configuration), or to be sent directly to a different DAQ device channel
(DTEMP configuration). In the MTEMP configuration, you can select the
temperature sensor in software using the
SCXI_Single_Chan_Setup
function. If you use the DTEMP configuration, the temperature sensor
output appears on DAQ device channel 15 for the SCXI-1120/D, and
channel 4 for the SCXI-1121. To read the temperature sensor in the
DTEMP configuration with the SCXI-1120/D, the DAQ device must be in
NRSE mode. When you use the SCXI-1320, multiply the voltage you read
from the temperature sensor by 100 to get degrees Celsius. The SCXI-1328
temperature sensor is a thermistor; you can use the thermistor conversion
routine described in Chapter 5, Transducer Conversion Functions in the
NI-DAQ User Manual for PC Compatibles to convert the thermistor
voltage to temperature.
You can use the SCXI-1321 terminal block only with the SCXI-1121
(Revision C and later). In addition to the features of SCXI-1320, the
SCXI-1321 also has shunt resistors that you can enable using the