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National Instruments Corporation
11
SCXI-1313 Installation Guide
Temperature Sensor Output and Accuracy
The SCXI-1313 temperature sensor outputs 1.91 to 0.65 V from 0 to 50 °C.
Converting a Thermistor Voltage to a Temperature
National Instruments software can convert a thermistor voltage to the
thermistor temperature for the circuit diagram shown in Figure 3.
In LabVIEW, you can use the Convert Thermistor Reading VI found in the
Data Acquisition»Signal Conditioning
palette. If you are using 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.
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-1313
Page 14: ......
