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NI 9214 Operating Instructions and Specifications
12
ni.com
Yo
u
can connect a shielded thermoco
u
ple to the NI 9214. Connect
the shield to the gro
u
nd l
u
g on the NI TB-9214 and COM to a
common-mode voltage reference on the thermoco
u
ple. A valid
common-mode voltage reference is a voltage that is within ±1.2 V
of the common-mode voltage of the thermoco
u
ple. If COM is left
floating, the internal common-mode voltage of the inp
u
t circ
u
itry
is the average of all the inp
u
ts. Refer to the
section
for more information abo
u
t the common-mode voltage. The shield
gro
u
nding methodology can vary depending on the application.
Refer to Fig
u
re 4 for an ill
u
stration of a typical shielding
config
u
ration.
Figure 4.
Connecting a Shielded Thermocouple Input Signal to the NI 9214
Thermoco
u
ple
TC–
COM
TC+
S
hield
NI
TB-9214
NI 9214
Ch
ass
i
s
Gro
u
nd
Gro
u
nd
L
u
g
NI_9214.fm Page 12 Monday, November 1, 2010 9:52 AM