LM35 Temperature Sensor

Active Analog Temperature Sensors :

There are varieties of analog temperature sensors around us. The main function of a active analog temperature sensor IC is to provide an output as voltage which is proportional to the temperature of the surroundings. Few of them are LM34, LM35, TMP 35/36/37, MCP9071 etc. These devices does not require any external calibration. A simple ADC (Analog to Digital Conversion) required for digital processing. 


Quick overview on the LM35 Analog Temperature Sensor


LM35 Temperature Sensor


  • Low cost, well available Analog Temperature Sensor
  • Calibrated directly in ° Celsius (Centigrade)
  • Linear + 10 mV/°C Scale Factor
  • 0.5°C Ensured Accuracy (at +25°C)
  • Rated for Full −55°C to +150°C Range
  • Low Self-Heating
  • Low impedance output, 0.1W for 1 mA Load
  • Operates from 4 to 30 V
  • Also suitable for Remote Applications



 Pin Configuration : Pin 1 : +Vcc (4 to 20 V ) , Pin 2 : Output, Pin 3 : Ground (GND)

LM35 pinout
LM35 Pin Configuration




It is very interesting to work with new things, when a primary stage of testing success brings mental satisfaction on the work & we go for more advanced implementation which increases the knowledge & allow us to think and face practical.

As LM35 is calibrated  directly in ° Celsius (Centigrade), so using only a multimeter it can be used as a digital thermometer for both Basic Centigrade Temperature Sensor & Full-Range Centigrade Temperature Sensor. Fig. 1 & Fig. 2 describes the circuit for those.


circuit 1
Basic Centigrade Temperature Sensor
circuit 2
Full-Range Centigrade Temperature Sensor


The Basic one on the breadboard

Breadboard Setup

Breadboard wiring


Use heat sink tubes for insulation between three pins

Time to test!

room temperature
Normal Room Temperature which is 32.8 ° C
Increase in room temperature when a hot object is placed near the sensor (36.3 ° C)
Temperature decreasing to room temperature when hot object is removed

Leave a reply if I missed anything! 

Written by : Subhadeep Biswas