User Manual

4WFB120, 4WFB350, 4WFB1K 4 Wire Full Bridge Terminal Input Modules
Subtracting the unstrained (zero) result from the strained result gives
V
r
:
V
Vout
Vin
Vout
Vin
RR
RR R
R
RR
RR
RR R RR
r
strained unstrained
gg
gg
g
g
g
gg g
=
⎛
⎝
⎜
⎞
⎠
⎟
−
⎛
⎝
⎜
⎞
⎠
⎟
=
+
++
−
+
=
⋅
++ ⋅ +
∆
∆
∆
∆
3
3
33
()()
3
6.6.
The terminal input module is selected so that
RR
g3
=
. Substituting
R
for
:
g
R
3
V
RR
RR R RR
RR
RRR
R
RR
r
gg
gg g gg
gg
ggg
g
gg
=
⋅
++ ⋅ +
=
⋅
+
=
+
∆
∆
∆
∆
∆
∆ ()()424
2
2
6.7.
Solving for strain:
(
)
()
42
42
42
412
RRV
RV RV R
RV R RV
RV R V
ggr
gr gr g
gr g gr
gr g r
+=
+=
=−
=−
∆∆
∆∆
∆∆
∆
R
g
4
12
V
V
R
R
r
r
g
g
−
=
∆
6.8.
Strain is calculated by dividing equation 6.8 by the gage factor. The units are
converted to microstrain by multiplying by 10
6
uS/S.
()
µε =
⋅
−
=
⋅
410
12
10
6
6
V
GF V
R
GF R
r
r
g
g
∆
6.9.
16