Temperature Measurement

Temperature sensor IC LM35

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The LM35 series temperature sensor is a temperature sensor in the form of an integrated circuit, where the output is a voltage that is linearly proportional to the Celsius temperature (Centigrade). So LM35 has a feature compared to a linear temperature sensor which is usually expressed in Kelvin, ie the user does not need to reduce the sensor output with a constant number of 273 0.

Characteristics of IC LM35:

  • LM35 does not require external calibration, with an accuracy of ± ¼ ° C at room temperature, or ± ¾ ° C for the measurement range of -55 to + 150 ° C.
  • It has a low output impedance, linear output, easy to operate and combined with the next circuit such as the control circuit.
  • LM35 can be operated with a single power supply or dual power supply (plus and minus), and only requires 60 μA of current, the heat produced is not too high (less than 0.1 ° C) even without cooling.
  • LM35 is able to measure temperature with a range of -55 ° to + 150 ° C, while for the LM35C series it has a measurement range of -40 ° to + 110 ° C.

The LM35 series packaging is in the same shape as the TO-46 transistor packaging, while the LM35C, LM35CA and LM35D series are also available in TO-92 packaging, and the LM35D series are also available in TO-220 packaging.

LM35 circuit diagram:

LM35 Circuit Diagram

The circuit of the temperature sensor has terminals as two inputs, such as not invert (+) and invert (-) and only one output pin. The operational amplifier IC741 is used as a non-inverting amplifier. The variation between the terminals I/p amplifies the circuit.

This unstable voltage is supplied to a comparator IC 741. OP Amplifier is the electronic device most used today. The operational amplifier IC 741 is a type of differential amplifier. We have used IC741 as a non-inverting amplifier, which means that the pin-3 is the input and the output is not inverted. This LM35 temperature sensor circuit amplifies the difference between its input terminals.



Instrumentation Engineer

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