National Instruments SCC-TC Series, Руководство пользователя

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© National Instruments Corporation 7 SCC-TC Series Thermocouple Input Modules User Guide
Using the TC0 X
Scaling Voltage Measurements
Note NI-DAQ includes thermocouple and thermistor conversion utilities that implement
the conversions required in steps 3 and 5 of the following procedure. Refer to your
software documentation for more information on these utilities.
Your software environment may return only voltage measurements from
E Series DAQ devices. If so, you must convert voltage measurements to
temperature measurements. To make this conversion, complete the
following steps:
1. Measure the thermocouple voltage.
a. Read the thermocouple channel on the E Series DAQ device
V
ESERIES
[CH( X )].
b. Calculate the thermocouple voltage by using the following
formula:
where
V
TC
is thermocouple voltage.
V
ESERIES
is E Series DAQ device voltage.
This step provides proper scaling for the thermocouple amplifier in the
SCC-TC0
X .
2. Measure the reference-junction (cold-junction) temperature.
a. Read the thermistor voltage [AI ( X
+
8)].
b. Convert the thermistor voltage to cold-junction temperature using
the formula in the
Cold-Junction Sensor section.
3. Calculate the cold-junction compensation voltage by converting the
cold-junction temperature from step 2 to a thermocouple voltage. Use
the polynomial expressions applicable to the type of thermocouple you
are using.
4. Apply the cold-junction compensation to the thermocouple reading
by adding the cold-junction compensation voltage from step 3 to
V
TC
.
5. Calculate the thermocouple temperature by converting the voltage
result from step 4 to a temperature. Use the polynomial expressions
applicable to the type of thermocouple you are using. This calculation
gives you a linearized temperature measurement.
Note
Polynomials are from NIST Monograph 175.
V
TC
V
ESERIES
100
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