NI WSN-3214 User Guide and Specifications
17
ni.com
Figure 13.
Quarter-Bridge Type I Measuring Axial and Bending Strain
A quarter-bridge type I configuration has the following characteristics:
•
A single active strain-gage element is mounted in the principal direction of axial or bending strain.
•
A passive quarter-bridge completion resistor (R
3
) is required in addition to half-bridge completion
resistors (R
1
and R
2
). All of these resistors are provided by the NI WSN-3214 module.
•
Sensitivity ~ 0.5
μ
V/V per
με
, for GF = 2.0.
Figure 14.
Quarter-Bridge I Circuit Diagram
The following symbols apply to the circuit diagram and equations:
•
R
1
and R
2
—Half-bridge completion resistors located inside the NI WSN-3214.
•
R
3
—Quarter-bridge completion resistor located inside the NI WSN-3214
.
You can select to use a
bridge completion of 350
Ω
or 1 k
Ω
.
•
R
3
must be equal to the nominal resistance of the active gage (R
4
).
•
R
4
—Active element measuring tensile strain (+
ε
). You provide this element.
•
GF
—Gage Factor, specified by the gage manufacturer.
•
V
EX
—Excitation voltage provided by the NI WSN-3214.
R
4
(+ )
Axi
a
l
Bending
R
4
(+ )
V
CH
V
EX
R
1
R
2
R
3
R
4
(+
ε
)
+
–
NI W
S
N-
3
214
R
COMP
/EX–
AI+
EX+
+
–
