National Instruments SCXI-1321 Installation Manual page 10

SCXI-1121
+
–
R
1
+
4.5 kΩ
V
EX
–
4.5 kΩ
R
2
Note: R and R are completion resistors.
1 2
SCXI-1321 Terminal Block Installation Guide
Assuming a strain-gauge range with a gauge factor of GF = 2 and a
quarter-bridge configuration, this range corresponds to ±1,498 µε, as given
by the strain formula for a quarter-bridge strain-gauge configuration:
where
strained voltage static unstrained voltage
V
= ------------------------------------------------------------------------------------------------------- -
r
SCXI-1321
CH+ CH+
R
SCAL
301 kΩ
CH–
EX+
R
Trim
10 kΩ
39.1 kΩ
EX–
4V
–
ε
= -------------------------------
(
GF 1
+
–
V
exc
CH+
CH–
EX+
R
Null
EX–
R
Trim
Figure 3. Quarter-Bridge Nulling Circuit
10
r
)
2V
r
Transducer
R
L
EX+
R
R
L
R
L
R (dummy)
3
(Screw Adjusts Potentiometer)
(gauge)
4
CH+
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