®

INA131

9

INA131

V

IN

–

V

IN

+

OPA602

1M

Ω

1M

Ω

Ref

V

O

Common-mode resistors have

approximately 0.1% effect

on gain.

100

Ω

Shield is driven at the

common-mode potential.

FIGURE 4. Shield Driver Circuit.

INA131

Ref

V

O

100µA

V+

V+

R

Z

RTD

1

2

3

Equal line resistance here creates

a small common-mode voltage

which is rejected by INA131.

Resistance in this line causes

a small common-mode voltage

which is rejected by INA131.

V

O = 0V at RRTD = RZ

REF200

FIGURE 5. RTD Temperature Measurement Circuit.

FIGURE 6. Thermocouple Amplifier with Cold Junction Compensation.

SEEBECK

ISA

COEFFICIENT

R2

R4

TYPE

MATERIAL

(

µV/°C)

(R3 = 100Ω)(R5 + R6 = 100Ω)

E

Chromel

58.5

3.48k

Ω

56.2k

Ω

Constantan

J

Iron

50.2

4.12k

Ω

64.9k

Ω

Constantan

K

Chromel

39.4

5.23k

Ω

80.6k

Ω

Alumel

T

Copper

38.0

5.49k

Ω

84.5k

Ω

Constantan

NOTES: (1) –2.1mV/

°C at 200µA. (2) R

7 provides down-scale burn-out indication.

REF102

R

80.6k

4

Ω

R

1M

7

Ω

R

5.23k

2

Ω

R

27k

1

Ω

R

100

3

Ω

1N4148

Cu

Cu

R

50

5

Ω

R

100

Zero Adj

6

Ω

V+

K

6

10.0V

4

(1)

(2)

2

INA131

V

O

Ref