LM35 Temperature Sensor – Precision Analog Temperature Sensor

The LM35 Temperature Sensor is a high-precision integrated circuit temperature sensor designed to accurately measure temperature and provide an analog output voltage directly proportional to the temperature in degrees Celsius (°C). Unlike many temperature sensors that require calibration or complex signal conditioning, the LM35 is factory calibrated, ensuring reliable and accurate temperature measurements without the need for external adjustments.

The sensor produces a linear analog output of 10 mV per degree Celsius, making it simple to interface with Analog-to-Digital Converters (ADCs) and popular microcontroller platforms such as Arduino, ESP32, ESP8266, Raspberry Pi (with an external ADC), STM32, PIC, AVR, NodeMCU, and PLC systems. Its low power consumption, minimal self-heating, and excellent long-term stability make it suitable for continuous temperature monitoring in a wide range of electronic and industrial applications.

The LM35 can measure temperatures from -55°C to +150°C, making it suitable for environmental monitoring, industrial process control, home automation, HVAC systems, laboratory equipment, battery temperature monitoring, and educational electronics projects. Its simple three-pin configuration allows quick integration into electronic circuits without requiring additional calibration circuitry.

Because of its accuracy, reliability, and ease of use, the LM35 remains one of the most widely used analog temperature sensors for embedded systems, automation, and research applications.

Working Principle

The LM35 operates using a precision semiconductor temperature sensing circuit integrated inside the IC. As the surrounding temperature changes, the sensor generates an output voltage that changes linearly with temperature.

The output voltage increases by 10 millivolts (mV) for every 1°C increase in temperature. For example, the sensor outputs approximately 250 mV at 25°C, 500 mV at 50°C, and 1 V at 100°C.

This analog voltage is measured by the Analog-to-Digital Converter (ADC) of a microcontroller, which converts the voltage into digital values. Using the known conversion factor of 10 mV/°C, the controller calculates and displays the actual temperature accurately.

The factory calibration and linear output eliminate the need for complex compensation circuits, enabling simple and reliable temperature measurement.

Key Features

High-precision analog temperature sensor.

Factory calibrated directly in degrees Celsius (°C).

Linear analog output of 10 mV/°C.

Wide temperature measurement range from -55°C to +150°C.

No external calibration required.

Low self-heating for improved accuracy.

Excellent long-term stability.

Low power consumption.

High measurement accuracy.

Simple three-pin interface.

Fast response to temperature changes.

Compact TO-92 package.

Easy integration with microcontrollers and ADC circuits.

Compatible with Arduino, ESP32, ESP8266, Raspberry Pi (with external ADC), STM32, PIC, AVR, NodeMCU, and PLC systems.

Suitable for industrial, educational, and DIY electronics projects.

Technical Specifications

Sensor Type: Analog Temperature Sensor

Sensor IC: LM35

Output Type: Analog Voltage

Output Scale Factor: 10 mV/°C

Temperature Range: -55°C to +150°C

Operating Voltage: 4V–30V DC

Supply Current: Typically less than 60 µA

Accuracy: Typically ±0.5°C at 25°C (model dependent)

Calibration: Factory Calibrated in Celsius

Self-Heating: Very Low

Response Time: Fast

Package Type: TO-92

Operating Temperature: -55°C to +150°C

Applications

Temperature monitoring systems.

Industrial process control.

HVAC systems.

Environmental monitoring.

Weather stations.

Battery temperature monitoring.

Power supply temperature protection.

Smart home automation.

IoT monitoring systems.

Medical and laboratory equipment.

Embedded system development.

Educational electronics projects.

Research and laboratory experiments.

DIY electronics projects.

Automation and control systems.