©
National Instruments Corp.
9
NI 9217 Operating Instructions and Specifications
Figure 3.
Input Circuitry for One Channel of the NI 9217 in 4-Wire Mode
Each channel has one terminal, RTD+, to which yo
u
connect the
positive lead of the RTD signal and one terminal, RTD–, to which
yo
u
connect the negative lead of the RTD signal. Each channel also
has a common terminal, COM, and an excitation c
u
rrent so
u
rce
terminal, EX. Yo
u
m
u
st connect the COM terminal to RTD–. All
fo
u
r COM terminals are internally connected to the isolated gro
u
nd
reference of the mod
u
le. If yo
u
are
u
sing shielded wiring, connect
one end of the shield to the COM terminal. Refer to Fig
u
re 4 for an
ill
u
stration of how to connect an RTD to the NI 9217.
NI 9217
ADC
4-Wire EX
COM
RTD+
RTD–
Excitation
Current
Filtered
Amplifier
3-wire & 4-wire
Detection &
Compensation
