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SCC-TC Series Thermocouple Input Modules User Guide 8 ni.com
Cold-Junction Sensor
The cold-junction sensor voltage output varies from 1.91 to 0.58 V over a
0 to 55 °C temperature range.
Note NI-DAQmx includes thermistor conversion utilities that implement the equations
listed below. Refer to your software documentation for more information on these utilities.
You can use the following formulas to convert the cold-junction sensor
voltage to cold-junction temperature:
where T
K
is the temperature in degrees kelvin.
where
a = 1.295361 × 10
–3
b = 2.343159 × 10
–4
c = 1.018703 × 10
–7
R
T
is the resistance of the thermistor in ohms.
where V
TEMPOUT
is the output voltage of the cold-junction sensor.
where T(°F) and T(°C) are the temperature readings in degrees Fahrenheit
and Celsius, respectively.
Note 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 range on the analog input channel.
For the cold-junction sensor measurement accuracy, refer to the
Specifications section.
For more information about how to configure the SCC-TC0X using
NI-DAQmx, refer to the SCC Quick Start Guide.
T °C() T
K
273.15–=
T
K
1
ab Rln
T
()cRln
T
()
3
++[]
--------------------------------------------------------------=
R
T
5,000
V
TEMPOUT
2.5 V
TEMPOUT
–
--------------------------------------
⎝⎠
⎛⎞
=
T °F()
T °C()]9[
5
------------------------ 32+=