7

The AD590 produces a temperature-dependent voltage

scale-zero voltage. For the celsius scale, make R = 1k

Ω

Meter displays current output directly in degrees Kelvin.

using the AD590J, sensor output is within

±10 degrees over

the entire range. See Figure 10.

ALL values are in k

Ω.

(V+ -0.5V) to (V- +1V). R is scaled to bring each range within

limited by the (short-term) maximum allowable sensor tem-

perature. Maximum reading on the fahrenheit range is

See Figure 11 and notes below.

The

Kelvin

scale

version

reads

from

0

to

Ω

general-purpose silicon diodes or an LED may be substi-

tuted. See Figure 12 and notes below.

This circuit allows “zero adjustment” as well as slope

adjustment. the ICL8069 brings the input within the com-

mon-mode range, while the 5k

Ω pots trim any offset at

notes below.

Notes for Figure 11, Figure 12 and Figure 13

of ICL7106 components can be made to lower noise and

9.00

4.02

2.0

12.4

10.0

0

5.00

4.02

2.0

5.11

5.0

11.8

+

-

AD590

+

-

M

<30V

500

µA

FIGURE 10. SIMPLEST THERMOMETER

V+

REF HI

REF LO

ICL7106

IN HI

COMMON

IN LO

R

+

-

V

-

AD590

FIGURE 11. BASIC DIGITAL THERMOMETER, CELSIUS AND

FAHRENHEIT SCALES

R

n

n1

=

5

∑

28k

Ω

=

nominal

V+

7.5k

Ω

2.26k

Ω

+

-

V

-

5k

Ω

15k

Ω

1.00k

Ω

AD590

SCALE

ADJ

REF HI

REF LO

ICL7106

IN HI

COMMON

IN LO

FIGURE 12. BASIC DIGITAL THERMOMETER, KELVIN SCALE

V+

7.5k

Ω

1k

Ω

+

-

V

-

5k

Ω

15k

Ω

AD590

SCALE

ADJ

0.1%

1.000V

12k

Ω

ZERO

ADJ

26.1k

Ω

5k

Ω

402

Ω

ICL8069

1.235V

REF HI

REF LO

ICL7106

IN HI

COMMON

IN LO

FIGURE 13. BASIC DIGITAL THERMOMETER, KELVIN SCALE

WITH ZERO ADJUST

AD590