©
National Instruments Corporation
13
TBX-1328 Installation Guide
Reading the Temperature Sensor in LabVIEW
Notes
This section does not apply to the SCXI-1126.
When using virtual channels, select
Built-in
as the source of the CJC and NI-DAQ will
perform compensation automatically for that thermocouple channel. You do not need to
use
mtemp
.
In LabVIEW, the channel string used to read
V
TEMPOUT
depends on which
module is connected to the TBX-1328. For more information about
channel-string arrays and the SCXI channel-addressing syntax, refer to the
LabVIEW Measurements Manual
, which you can download at
ni.com/manuals
.
•
With the SCXI-1120/D, or SCXI-1121, use the address string:
ob
x
! sc
y
! md
z
! mtemp
You
cannot
put this channel-address string in the same channel-string
array as other channels on the module that you are addressing.
•
With the SCXI-1125, use the address string:
ob
x
! sc
y
! md
z
! cjtemp
You can put this channel-address string in the same channel-string
array as other channels on the same SCXI-1125 module, but it must be
the first channel scanned on the SCXI-1125.
Reading the Temperature Sensor in NI-DAQ
Refer to the
NI-DAQ Function Reference Manual
for the description for
reading the temperature sensor using the
SCXI_Single_Chan_Setup
,
SCXI_Change_Chan
, and
SCXI_SCAN_Setup
functions.
Note
The method for scanning the temperature sensor on the SCXI-1125 with other
channels on the same module using the
SCXI_SCAN_Setup
is the same as that of the
SCXI-1102.
Strain Measurement Considerations
When you use the SCXI-1121 with the TBX-1328 to measure strain, a
small amount of voltage drop develops across the excitation wires in the
SH32-32-A cable. This voltage drop is due to the wire resistance and the
current flow in these leads when a strain gauge is connected at the
TBX-1328 across the excitation outputs provided on the SCXI-1121.
To reduce errors in the output voltage, first calculate the voltage drop across
the SH32-32-A cable. This voltage drop results in a measurement error that
