SCXI-1328 Installation Guide
4
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Temperature Sensor Output and Accuracy
The SCXI-1328 temperature sensor outputs 1.91 to 0.58 V from 0 to 55 °C
and has an accuracy of ±0.5 °C over the 15 to 35 °C range and ±0.9 °C over
the 0 to 15 °C and 35 to 55 °C ranges
1
.
National Instruments software can convert a thermistor voltage to the
thermistor temperature for the circuit diagram shown later in this guide.
In LabVIEW, you can use the Convert Thermistor Reading VI in the
Data Acquisition»Signal Conditioning palette. If you are using
LabWindows/CVI or NI-DAQ, use the
Thermistor_Convert
function.
The VI takes the output voltage of the temperature sensor, the reference
voltage, and the precision resistance and returns the thermistor temperature.
Alternatively, you can use the following formulas:
T(°C) = T
K
– 273.15
where T
K
is the temperature in kelvin
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.
Note
Use an average of a large number of samples to obtain the most accurate reading.
Noisy environments require more samples for greater accuracy.
1
Includes the combined effects of the temperature sensor accuracy and the temperature difference between the temperature
sensor and any screw terminal. The temperature sensor accuracy includes tolerances in all component values, the effects
caused by temperature and loading, and self-heating.
T
K
1
a
b
R
T
ln
(
)
c
R
T
ln
(
)
3
+
+
[
]
--------------------------------------------------------------
=
R
T
5 000
V
TEMPOUT
2.5
V
TEMPOUT
–
--------------------------------------
,
=
T
°
F
( )
[T(
°
C
) ]
9
5
-----------------------
32
+
=
Summary of Contents for SCXI-1328
Page 10: ......
