V+
1/2
R2
R1
VOUT = (V1 – V2)(1 +
)
OPA2277
R2
V–
V+
R–∆R
R+∆R
R+∆R
V2
R1
Load
Cell
V1
1/2
R–∆R
OPA2277
V–
R2
R1
For integrated solution see: INA126, INA2126 (dual)
INA125 (on-board reference)
INA122 (single-supply)
FIGURE 3. Load Cell Amplifier.
IREG 1mA
5V
12
1
V+
VLIN
VI+N
14
IR1
1/2
13
11
VREG
IR2
10
V+
OPA2277
Type J
RF
10kΩ
4
RG
RG
1250Ω
9
8
B
E
R
412Ω
XTR105
RF
10kΩ
3
RG
VI–N
IO
1/2
OPA2277
2
7
1kΩ
25Ω
IRET
IO = 4mA + (VI+N – VI–N
)
40
RG
V–
6
50Ω
RCM = 1250Ω
2RF
R
(G = 1 +
= 50)
0.01µF
FIGURE 4. Thermocouple Low Offset, Low Drift Loop Measurement with Diode Cold Junction Compensation.
OPA277, OPA2277, OPA4277
10
SBOS079A
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