AD590JRZ-RL View Datasheet(PDF) - Analog Devices

Part Name

Description

MFG CO.

AD590JRZ-RL

2-Terminal IC Temperature Transducer

Analog Devices 

AD590

GENERAL APPLICATIONS

Figure 16 demonstrates the use of a low cost digital panel meter

for the display of temperature on either the Kelvin, Celsius, or

Fahrenheit scales. For Kelvin temperature, Pin 9, Pin 4, and

Pin 2 are grounded; for Fahrenheit temperature, Pin 4 and Pin 2

are left open.

5V

6

8

9

+

AD590

–

AD2040

4

5

3

2

OFFSET

CALIBRATION

GAIN

SCALING

OFFSET

SCALING

GND

Figure 16. Variable Scale Display

The above configuration yields a 3-digit display with 1°C or 1°F

resolution, in addition to an absolute accuracy of ±2.0°C over

the −55°C to +125°C temperature range, if a one-temperature

calibration is performed on an AD590K, AD590L, or AD590M.

Connecting several AD590 units in series, as shown in Figure 17,

allows the minimum of all the sensed temperatures to be

indicated. In contrast, using the sensors in parallel yields the

average of the sensed temperatures.

15V

10kΩ

(0.1%)

+

AD590

–

+

AD590

–

+

AD590

–

+

VT MIN

–

5V

+

+

–

–

+

AD590

–

333.3Ω

(0.1%)

+

VT AVG

–

Figure 17. Series and Parallel Connection

The circuit in Figure 18 demonstrates one method by which

differential temperature measurements can be made. R1 and R2

can be used to trim the output of the op amp to indicate a

desired temperature difference. For example, the inherent offset

between the two devices can be trimmed in. If V+ and V− are

radically different, then the difference in internal dissipation

causes a differential internal temperature rise. This effect can be

used to measure the ambient thermal resistance seen by the

sensors in applications such as fluid-level detectors or anemometry.

+

AD590L

– #2

V+

R3

10kΩ

+

AD590L

– #1

R2

50kΩ

R1

5MΩ

R4

10kΩ

–

AD707A

+

(T1 – T2) × (10mV/°C)

V–

Figure 18. Differential Measurements

Figure 19 is an example of a cold junction compensation circuit

for a Type J thermocouple using the AD590 to monitor the

reference junction temperature. This circuit replaces an ice-bath

as the thermocouple reference for ambient temperatures

between 15°C and 35°C. The circuit is calibrated by adjusting RT

for a proper meter reading with the measuring junction at a

known reference temperature and the circuit near 25°C. Using

components with the TCs as specified in Figure 19, compensation

accuracy is within ±0.5°C for circuit temperatures between

15°C and 35°C. Other thermocouple types can be accommodated

with different resistor values. Note that the TCs of the voltage

reference and the resistors are the primary contributors to error.

7.5V

+ AD580

– VOUT

+

AD590

–

52.3Ω

8.66kΩ

RT

1kΩ

REFERENCE

JUNCTION

+

–

CU

+–

METER

IRON

CONSTANTAN

MEASURING

JUNCTION

RESISTORS ARE 1%, 50ppm/°C

Figure 19. Cold Junction Compensation Circuit for Type J Thermocouple

Rev. E | Page 10 of 16

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