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Número de pieza

componentes Descripción

Fabricante

LM135

PRECISION TEMPERATURE SENSORS

STMicroelectronics 

LM135-LM235-LM335,A

APPLICATION HINTS

There is an easy method of calibrating the device for

higher accuracies (see typical applications).

The single point calibration works because the out-

put of the LM135, LM235, LM335 is proportional to

the absolute temperature with the extrapolated out-

put of sensor going to 0V at 0oK ( –273.15oC). Errors

in outputvoltage versus temperature are only slope.

Thus a calibration of the slope at one temperature

corrects errors at all temperatures.

The output of the circuit (calibrated or not) can be

given

by

the

equation

:

VOT

=

VOTO

x

T

To

where T is the unknown temperature and TO is the

reference temperature (in oK).

TYPICAL APPLICATIONS

BASIC TEMPERATURE SENSOR

Nominally the output is calibrated at 10mV/oK.

Precautions should be taken to ensure good sens-

ing accuracy. As in the case ofall temperaturessen-

sors, self heating can decrease accuracy. The

LM135, LM235, LM335 should operate with a low

current, but sufficient to drive the sensor and its cali-

bration circuit to their maximum operating tempera-

ture.

If the sensor is used in surroundings where the ther-

mal resistane is constant,the errors due to self heat-

ing can be externally calibrated. This is possible if

the circuit is biased with a temperature stable cur-

rent. Heating will then be proportional to zener volt-

age and therefore temperature. In this way the error

due to self heating is proportional to the absolute

temperature as scale factor errors.

WIDE OPERATING SUPPLY

V

LM135

LM235

LM335

R1

Output

10mV/°K

Vi

+5 to +40V

LM134, LM234

LM334

LM135

LM235

LM335

68Ω

Output

10mV/°K

CALIBRATED SENSOR

V

LM135

LM235

LM335

R1

Output

10mV/°K

10kΩ*

AVERAGE TEMPERATURE SENSING

+15V

6kΩ

Output

30mV/°K

LM135

LM235

LM335

* Calibrate for 2.982V at +25oC

6/11

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