Programming instructions

Chapter 21 Common SCXI Applications
© National Instruments Corporation 21-9 LabVIEW Data Acquisition Basics Manual
Figure 21-4.
Continuously Acquiring Data Using Intermediate VIs
Another temperature acquisition example using the SCXI-1100 module is
SCXI Temperature Monitor VI located in
labview\examples\daq\
scxi\scxi_ai.llb
. This VI continually acquires thermocouple readings
and sets an alarm if the temperature readings go above a user-defined limit.
You can use the SCXI-1100 examples with the SCXI-1122 module.
Both modules have the capability to programmatically measure the
amplifier offsets and both modules need the cold-junction compensation
to linearize thermocouple measurements. The main differences between
the two modules include the type of temperature sensors available on
their terminal blocks and the way module channels are multiplexed. The
SCXI-1100 uses a CMOS multiplexer, which is capable of fast-channel
multiplexing, whereas the SCXI-1122 uses a electromechanical relay to
switch one of its 16 channels. Because the SCXI-1122 uses a relay, this
module imposes a minimum interchannel delay of 10 ms. Scanning
multiple SCXI-1122 channels many times can quickly wear out the relay.
To avoid this, acquire data from the SCXI-1122 module a single channel
at a time. For further information on reading SCXI-1122 channels, refer to
the
SCXI-1122 User Manual
, or the SCXI-1122 Voltage example VI in
labview\examples\ daq\scxi\scxi_ai.llb
.