National Instruments SCC-TC02 Benutzerhandbuch
SCC-TC Series Thermocouple Input Modules User Guide
6
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temperature measurements. To make this conversion, complete the
following steps:
following steps:
1.
Measure the thermocouple voltage.
a.
Read the thermocouple channel on the E/M Series DAQ device
V
V
ESERIES
[CH(X)].
b.
Calculate the thermocouple voltage by using the following
formula:
formula:
where
V
TC
is thermocouple voltage.
V
ESERIES
is E/M Series DAQ device voltage.
This step provides proper scaling for the thermocouple amplifier in the
SCC-TC0X.
SCC-TC0X.
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
the formula in the
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.
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
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.
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.
Uncompensated Connectors and Accuracy
If you are using an SCC-TC02 with an uncompensated SCC panelette,
temperature gradients between the module and the junctions on the
panelette affect the accuracy of the measurements.
temperature gradients between the module and the junctions on the
panelette affect the accuracy of the measurements.
V
TC
V
ESERIES
100
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