V+
1/2
OPA2277
R
2
V–
V
OUT
= (V
1
– V
2
)(1 +
R
2
R
1
)
R–∆R
V
1
R+∆R
Load
Cell
R+∆R
V
2
R–∆R
V+
R
1
1/2
OPA2277
V–
R
2
R
1
For integrated solution see: INA126, INA2126 (dual)
INA125 (on-board reference)
INA122 (single-supply)
FIGURE 3. Load Cell Amplifier.
I
REG
∼
1mA
5V
12
V+
Type J
1/2
OPA2277
R
F
10kΩ
R
412Ω
13
V
LIN
V
IN
4
R
G
1250Ω
3
R
G
–
V
IN
+
1
I
R1
14
I
R2
11
10
V+
V
REG
R
G
XTR105
B
E
I
O
9
R
F
10kΩ
8
1kΩ
50Ω
25Ω
R
CM
= 1250Ω
1/2
OPA2277
V–
2
7
6
+
–
I
O
= 4mA + (V
IN
– V
IN
) 40
R
G
I
RET
(G = 1 +
0.01µF
2R
F
= 50)
R
FIGURE 4. Thermocouple Low Offset, Low Drift Loop Measurement with Diode Cold Junction Compensation.
®
9
OPA277, 2277, 4277