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 0

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

T

reference temperature (in

Nominally the output is calibrated at 10mV/

Precautions should be taken to ensure good sens-

ing accuracy. As in the case of all 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.

LM135

LM235

LM335

V

R1

Output

10mV/

°K

TYPICAL APPLICATIONS

BASIC TEMPERATURE SENSOR

+5 to +40V

LM134, LM234

LM334

68

Ω

LM135

LM235

LM335

Output

10mV/

°K

WIDE OPERATING SUPPLY

LM135

LM235

LM335

V

R1

Output

10mV/

°K

10k

Ω*

* Calibrate for 2.982V at +25

CALIBRATED SENSOR

LM135

LM235

LM335

6k

Ω

Output

30mV/

°K

+15V

AVERAGE TEMPERATURE SENSING

LM135-LM235-LM335,A

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