Chapter 3
Connecting the Signals
©
National Instruments Corporation
3-19
DAQPad-MIO-16XE-50 User Manual
(V
in
+) + (V
in
–) added to the gain times (V
in
+) – (V
in
–) is within ±26 V of
AIGND. At gains of 1 and 2, this restriction is of little or no consequence,
but at gains of 10 and 100, this is roughly equivalent to restricting the two
input voltages to within ±8 V of AIGND.
External Current Excitation
The screw terminals labeled IEX+ and IEX– provide external current
excitation for temperature measurements using RTDs or thermistors.
IEX+ is the current output and IEX– is the current return. The constant
current source provides 100 µA of external excitation.
Figure 3-8 suggests how you can connect several RTDs in series to the
DAQPad-MIO-16XE-50 using four-wire measurement techniques.
To connect the current excitation to IEX+ and IEX
−
terminals, push
the slide switch labeled IEX to the ON position.
Note
If you do not externally connect IEX+ to IEX– and you want to perform
cold-junction sensor measurements, you must push the slide switch to the OFF position.
