©
National Instruments Corp.
15
NI 9237 Operating Instructions and Specifications
Excitation Voltages
Altho
u
gh the sensor ind
u
stry does not recognize a single standard
excitation voltage level, excitation voltage levels of between
2.5 V and 10 V are common. Yo
u
can program the NI 9237 to
s
u
pply 2.5 V, 3.3 V, 5 V, or 10 V of excitation voltage, and the
mod
u
le can provide
u
p to 150 mW of excitation power. Unless yo
u
s
u
pply external excitation voltage, National Instr
u
ments
recommends that yo
u
set the excitation voltage to a val
u
e that
keeps the total power below 150 mW. The NI 9237 a
u
tomatically
red
u
ces internal excitation voltages as needed to stay below
150 mW total power.
The power cons
u
med by a single bridge is
where
R
is the total
resistance of the bridge.
For a q
u
arter or half bridge,
R
is eq
u
al to two times the resistance
of each element. For a f
u
ll bridge,
R
is eq
u
al to the resistance of
each element.
V
e x
2
R
---------
