NI 9217 Operating Instructions and Specifications
8
ni.com
Yo
u
can connect any combination of 3-wire or 4-wire RTDs to
the NI 9217. Each NI 9217 channel contains circ
u
itry that
a
u
tomatically detects the type of RTD connected to the channel.
The NI 9217 scans all fo
u
r inp
u
t channels and a
u
tomatically
config
u
res each channel for the appropriate mode. In 4-wire mode,
the EX terminal is a 1 mA c
u
rrent so
u
rce. In 3-wire mode, the
RTD+ terminal is a 1 mA c
u
rrent so
u
rce. The NI 9217
compensates for the error that lead resistance ca
u
ses in 3-wire
mode. Refer to Fig
u
re 3 for an example of the inp
u
t circ
u
itry for
one channel of the NI 9217 in 4-wire mode.
Note
Yo
u
m
u
st
u
se 2-wire ferr
u
les to create a sec
u
re
connection when connecting more than one wire to a
single terminal on the NI 9217.
The NI 9217 channels share a common gro
u
nd that is isolated from
other mod
u
les in the system. Each channel is filtered and then
sampled by a 24-bit analog-to-digital converter (ADC).
