LM335AZT New original Board Mount Temperature Sensors Precision 1 Deg Cel transistors manufacturers

LM335AZT New original Board Mount Temperature Sensors Precision 1 Deg Cel transistors manufacturers

Features

■ Directly calibrated in °K

■ 1°C initial accuracy

■ Operates from 450µA to 5mA

■ Less than 1Ω dynamic impedance

Description

• The LM135, LM235, LM335 are precision temperature sensors which can be easily calibrated. They operate as a 2-terminal Zener and the breakdown voltage is directly proportional to the absolute temperature at 10mV/°K.
• The circuit has a dynamic impedance of less than 1Ω and operates within a range of current from 450µA to 5mA without alteration of its characteristics
• Calibrated at +25°C, the LM135, LM235, and LM335 have a typical error of less than 1°C over a 100°C temperature range. Unlike other sensors, the LM135, LM235, LM335 have a linear output.

Application information

• There is an easy method of calibrating the device for higher accuracies
• The single point calibration works because the output of the LM135, LM235, LM335 is proportional to the absolute temperature with the extrapolated output of sensor going to 0V at 0°K (-273.15°C). Errors in output voltage versus temperature are only slope. Thus a calibration of the slope at one temperature corrects errors at all temperatures.
• The circuit output (calibrated or not) is given by the equation:

     VOT + VOTO x where T is the unknown temperature and To is the reference temperature (in °K).

• Nominally, the output is calibrated at 10mV/°K.
• Precautions should be taken to ensure good sensing accuracy. As in the case of all temperatures sensors, self-heating can decrease accuracy. The LM135, LM235, and LM335 should operate with a low current but sufficient to drive the sensor and its calibration circuit to their maximum operating temperature
• If the sensor is used in surroundings where the thermal resistance is constant, the errors due to self-heating can be externally calibrated. This is possible if the circuit is biased with a temperature stable current. Heating will then be proportional to Zener voltage and therefore temperature. In this way, the error due to self-heating is proportional to the absolute temperature as scale factor errors.