Chapter 2 Configuration and Installation
© National Instruments Corporation 2-31 SCXI-1121 User Manual
a = 1.288 x 10–3
b = 2.356 x 10–4
c = 9.556 x 10–8
RT = resistance of the thermistor in Ω
VTEMPOUT = output voltage of the temperature sensor
where T (°F) and T (°C) are the temperature readings in degrees Fahrenheit
and degrees Celsius, respectively.
Terminal Block Jumper Configuration
In addition to the screw terminals, the terminal block has one jumper for
configuring the onboard temperature sensor. When you set jumper W1 on
the SCXI-1320 or SCXI-1328 (jumper W5 on the SCXI-1321) to the
MTEMP position, the jumper connects the temperature sensor output to the
SCXI-1121 output multiplexer. This is the factory setting. The DTEMP
position of jumperW1 (jumper W5 on the SCXI-1321) connects the
temperature sensor to the SCXI-1121 MCH4+ signal on the rear signal
connector.
In both MTS and DTS modes, the reference to the temperature sensor
signal is the SCXI-1121 analog ground that is connected to MCH0– in the
MTS mode and to MCH4– in the DTS mode. Notice that MCH4– is
continuously connected to the SCXI-1121 ground, whereas MCH0– is
switched through the output multiplexer.
One jumper block comprises both positions; therefore, you can use only
one type of configuration at a time. The parking position for the jumper
block is in the MTEMP position (the temperature sensor is disabled until
the RTEMP bit in the Configuration Register selects the sensor).
TK1
ab R
T
ln()cR
T
ln()
3
++[]
--------------------------------------------------------------=
RT50,000 VTEMPOUT
2.5 VTEMPOUT
–
--------------------------------------


=
T°F() T°C()[]9
5
----------------------- 32+=