Integrated Circuits

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Monday, September 10, 2018

LM335 - Precision Temperature Sensor

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.

LM335 - Precision Temperature Sensor

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.

LM335 - Precision Temperature Sensor

Above data from STMicro - Circuit shows a design using LM335 for Temperature Control.

LM335 Cold Junction Compensation

Temperature Sensors like Thermocouples need cold junction compensation as a part of front end signal conditioning, this is done at the terminal block where the Thermocouple wires are terminated. This design has to be more accurate and broad, if the design we make has to work well in both Tropical and Temperate Climate Zones.

Thermocouple Temperature using DPM or DMM

Temperature measurement and control uses the Thermocouple and the Seebeck Effect for measurement. The most common is J Type as it is affordable. K is better and works well even at higher temperatures too.

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