LM35 Temperature Sensor


As we all know what does a temperature sensor do. In simple words these are devices used to measure the temperature or heat of a medium. 

But we will discuss here how does they work and whatare the components used and what types of components or sensors are available 

for sensing the temperature. There are various types of temperature sensor such as thermistor, RTD, thermocouple and IC Sensor but we 

will here focus on integrated circuit (IC) temperature sensor.


What is an IC Temperature Sensor?

A two or three terminal integrated circuit temperature transducer that produces an output current proportional  to absolute temperature. 

The sensor package is small with a low thermal mass and a fast response time.The most common temperature range is 55 to 150°C 

(-58 to 302°F). The solid state sensor output can be analog or digital.

Why use IC Sensors in place of other technologies like Thermocouples, RTDs and Thermistors?

The analog IC solid state sensors provide an output as a voltage or current that is proportional with temperature without additional circuitry. 

The digital IC sensors provide an output that has been processed hrough an integral A/D converter and is ready for input into digital control 

and monitoring systems. The IC sensors do not require linearization or other circuitry. The cost of IC sensorsare also very competitive with, 

in some cases less costly than,RTD and thermistor sensors.


Pin No




Supply voltage; 5V (+35V to -2V)



Output voltage (+6V to -1V)



Ground (0V)


LM35 is a precision IC temperature sensor with its output proportional to the temperature (in oC). The sensor circuitry is sealed and therefore it is not subjected to oxidation and other processes. With LM35, temperature can be measured more accurately than with a thermistor. It also possess low self heating and does not cause more than 0.1 oC temperature rise in still air.  The operating temperature range is from -55°C to 150°C. The output voltage varies by 10mV in response to every oC rise/fall in ambient temperature,i.e., its scale factor is 0.01V/ oC.

How to use

A temperature sensor produces an analogue or digital output whose strength depends on the temperature of the sensor. Heat is conducted to the sensing element through the sensor’s package and its metal leads. In general, a sensor in a metal package will have a dominant thermal path through the package. For sensors in plastic packages, the leads provide the dominant thermal path.Therefore a board-mounted IC sensor will do a fine job of measuring the temperature of the circuit board.
If its needed to measure the temperature of something other than the circuit board, it should be ensured that the sensor and its leads are at the same temperature as the object you wish to measure. This usually involves making a good mechanical (and thermal) contact by attaching the sensor and its leads to the object being measured with thermally-conductive epoxy.
If a liquid’s temperature is to be measured, the sensor can be mounted inside a sealed-end metal tube and dipped into a bath, or screwed into a threaded hole in a tank. Temperature sensors and any accompanying wiring and circuits must be kept insulated and dry, to avoid leakage and corrosion.
Any linear circuit connected to wires in an uncongenial environment can have its performance adversely affected by intense electromagnetic sources such as relays, radio transmitters, motors with arcing brushes, etc, as its wiring can act as an aerial and the internal junctions can act as rectifiers. In such cases, a small bypass capacitor from the power supply pin to ground rail helps clean up power supply noise.

How to Measure Temperature

Simply make the connections with the micro-controller being used.  The analog voltage is independant of the power supply. formula to calculate the temperature from the output (Vout) of the LM35.

 Temp in °C = (Vout in mV) / 10


Download LM35 data sheet click here






Who's new

  • ravirajpatil871...
  • shubhambajoria
  • yassir
  • demiholyman890954
  • scottgillum51169040

Get Notified



We are Social


Subscribe to Syndicate