Chapter 4 Connecting and Using Accessories and Transducers
© National Instruments Corporation 4-5 Getting Started with SCXI
Onboard Temperature Sensors for Cold-Junction Compensation
The SCXI-1300, SCXI-1303, TBX-1303, SCXI-1320, SCXI-1321,
SCXI-1322, SCXI-1327, SCXI-1328, and TBX-1328 terminal blocks have
onboard temperature sensors for measuring ambient temperature inside the
terminal block. If you are measuring temperatures with thermocouples, you
can obtain a temperature from the onboard temperature sensor that you can
use for cold-junction compensation.
The voltage output from the onboard temperature sensor is multiplexed,
along with other signals from the SCXI module, to channel 0 on the DAQ
device. Read the temperature signal using the
SCXI_Single_Chan_Setup
call in NI-DAQ and specifying
Channel (–1) in software, or by using the LabVIEW channel string
MTEMP.
To scale the voltage reading from an SCXI-1300, SCXI-1320, or
SCXI-1321 to temperature, multiply the value by 100 to get a temperature
reading in degrees Celsius.
The SCXI-1303, TBX-1303, SCXI-1322, SCXI-1327, SCXI-1328, and
TBX-1328 use a thermistor to measure the temperature. To convert the
voltage reading to a temperature, use a thermistor conversion formula.
In LabVIEW, use the Convert Thermistor VI. In NI-DAQ, use the
Thermistor_Convert
function call. Refer to Transducer Conversion
Functions in the NI-DAQ User Manual for PC Compatibles,formore
information.
Table 4-2.
TBX Terminal Block Compatibility with SCXI Modules
SCXI Module TBX Terminal Block Cable Assembly
SCXI-1100/1102 TBX-1303 SH96-96 or R96-96
SCXI-1124 TBX-1325 SH48-48A
SCXI-1162/1162HV/1163/1163R TBX-1326 SH28-28B
SCXI-1120/1121/1125 TBX-1328 SH32-32A
All other SCXI modules TBX-24F —
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