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Chapter 2
Connecting Signals
NI PXI-4220 User Manual
2-6
ni.com
Quarter-Bridge Type II
This section provides information about connecting the quarter-bridge
strain-gauge configuration type II. Figure 2-5 shows the quarter-bridge
type II circuit wiring diagram. Refer to the
Quarter-Bridge Type II
section
of Chapter 4,
Theory of Operation
, for more information.
Figure 2-5.
Quarter-Bridge II Circuit Diagram
The following symbols apply to the circuit diagram and equations:
•
R
1
and R
2
are half-bridge completion resistors.
•
R
3
is the quarter-bridge temperature-sensing element (dummy gauge).
•
R
4
is the active element measuring tensile strain (+
ε
).
•
V
EX
is the excitation voltage.
•
R
L
is the lead resistance.
•
V
CH
is the voltage measured.
•
R
S
is shunt calibration resistor A.
Note
The quarter-bridge type II is often confused with the more commonly used
half-bridge type I. For more information, refer to the
Quarter-Bridge Type II
and
Half-Bridge Type I
sections of Chapter 4,
Theory of Operation
.
+
–
+
–
R
L
R
L
NI PXI-4220
Transducer
R
1
R
2
R
4
R
3
V
CH
Shunt
Cal A
R
L
R
S
V
EX
R
L
S+ (Pin 1)
P+ (Pin 2)
P– (Pin 7)
SCA (Pin 4)
SCCOM (Pin 5)
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