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National Instruments Corporation
5
SCXI-1303 Installation Guide
a = 1.295361
×
10
–
3
b = 2.343159
×
10
–
4
c = 1.018703
×
10
–
7
R
T
= resistance of the thermistor in ohms
V
TEMPOUT
= output voltage of the temperature sensor
where T(° F) and T(° C) are the temperature readings in degrees Fahrenheit
and degrees Celsius, respectively.
Notes
V
TEMPOUT
varies from 1.91 V (at 0° C) to 0.58 V (at 55° C). For best resolution,
use the maximum gain for this signal range on the analog input channel.
The SCXI-1102/B/C has a 2 Hz filter on the V
TEMPOUT
signal.
The SCXI-1100 does not have a filter on the V
TEMPOUT
signal. Therefore, use an
average of a large number of samples to obtain the most accurate measurement.
Noisy environments require more samples for greater accuracy.
Configuring the Resistor Networks
Note
A package of 10 M
Ω
resistor networks is included in the SCXI-1303 kit. If you are
using the SCXI-1102/B/C module, you can install these resistor networks as RP1,
RP2, RP3, and RP4. With this recommended configuration, it does not matter
whether the thermocouples are ground-referenced or floating.
The SCXI-1303 terminal block has a pullup resistor connected between
CH+ and +5 V and a bias resistor connected between CH– and chassis
ground. Figure 2 shows how the pullup and bias resistors are connected to
the CH± inputs.
R
T
5 000
V
TEMPOUT
2.5
V
TEMPOUT
–
------------------------------------------
,
=
T
°
F
( )
[T(
°
C
) ]
9
5
-----------------------
32
+
=
Summary of Contents for SCXI-1303
Page 11: ......
