LM 34 and LM 35 Integrated Circuits are precision temperature sensors widely used in temperature sensing applications. LM 34 senses temperature in Fahrenheit range while LM 35 senses temperature in Celsius (Centigrade) range. The output voltage of these sensors is linearly proportional to the temperature. Here explains the important features of LM 34 and LM35 sensors.
It is the Fahrenheit sensor and the output voltage is linear to the temperature in the Fahrenheit range. It can operate between -50 to + 300 F range and requires a single supply. The LM 34 has low output impedance, linear output and precise inherent calibration feature. Its draws minimum current of 75 uA during operation and has very low self heating property of less than 0.2 F at normal air temperature. The improved version LM 34 C is designed to sense temperature of -40 to + 230 Fahrenheit. It operates between 5 to 30 Volts DC.
It is the precision temperature sensor with output linearly proportional to the Celsius (Centigrade) temperature. Like LM 34, it also operates in single supply and draws only 60 uA current. Its self heating is as low as 0.1 degree at still air. LM 35 is rated to operate between -55 to +150 Degree Celsius. LM 35C operates between -40 to +110 Degree Celsius. Supply voltage required for LM 35 ranges between 4 to 30 Volts DC.
Typical Circuit to read temperature in Digital Multimeter
Pin Assignment of both LM 34 and 35 are the same.
Pin 1 – Vcc
Pin2 – Output
Pin 3 – Ground
LM 34 and LM 35 Temperature Sensors