AD590 데이터 시트보기 (PDF) - Analog Devices

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AD590

2-Terminal IC Temperature Transducer

Analog Devices 

AD590

GENERAL APPLICATIONS

Figure 17 shows a typical use of the AD590 in a remote

temperature sensing application. The AD590 is used as a

thermometer circuit that measures temperature from −55°C to

+150°C, with an output voltage of 1 mV/°K. Because the

AD590 measures absolute temperature (its nominal output is

1 mA/K), the output must be offset by 273.2 mA to read out in

degrees Celsius.

AD590

IT

+

7V

–

IT

IT

1k

0.1% LOW

TCR RESISTOR

1mV/k

Figure 17. Variable Scale Display

Connecting several AD590 units in series, as shown in Figure 18,

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 18. Series and Parallel Connection

The circuit in Figure 19 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.

Data Sheet

+

AD590L

– #2

V+

R3

10kΩ

+

AD590L

– #1

R2

50kΩ

R1

5MΩ

R4

10kΩ

–

OP177

+

(T1 – T2) × (10mV/°C)

V–

Figure 19. Differential Measurements

Figure 20 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 20, 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 20. Cold Junction Compensation Circuit for Type J Thermocouple

Rev. G | Page 10 of 16

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