BNC/TC-2095 Rack-Mount Adapter Installation Guide
12
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Alternatively, you can follow these steps to convert the cold-junction sensor
voltage to the cold-junction temperature.
1.
Calculate the resistance of the thermistor in
Ω
.
V
TEMPOUT
= output voltage of the temperature sensor
Note
V
TEMPOUT
varies from 1.91 VDC (at 0 °C) to 0.58 VDC (at 55 °C). For the best
resolution, use the maximum gain for this signal range on the analog input channel of the
E Series DAQ device.
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 an accurate measurement. For example, sample for
one second and average. Noisy environments require more samples for greater accuracy.
The SCXI-1102/B/C has a 2 Hz filter on the
V
TEMPOUT
signal input channel.
2.
Calculate the cold-junction temperature in Kelvin.
a
= 1.295361
×
10
–3
b
= 2.343159
×
10
–4
c
= 1.018703
×
10
–7
R
T
= resistance of the thermistor
3.
Convert the temperature to Celsius and Fahrenheit.
T
K
= temperature in Kelvin
where
T
(°F) and
T
(°C) are the temperature readings in degrees
Fahrenheit and Celsius, respectively.
R
T
5,000
V
TEMPOUT
2.5
V
TEMPOUT
–
---------------------------------------
=
T
K
1
a b
R
ln
T
(
)
c
R
ln
T
(
)
3
+
+
--------------------------------------------------------------
=
T
°
C
( )
T
K
273.15
–
=
T
°
F
( )
T
°
C
( )
[
]
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5
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+
=
