Sunday, February 3, 2013

Electronic Component LM35 as High Precision Temperature Sensor

Robometricschool. - When you want to make robot that can detect temperature in it's work you will need high quality sensor as electronic component. In the market there are many sensor electronic component that sell to the user. But if you want to get high precision temperature sensor, i suggest you to choose LM35 as temperature sensor.

Figure 1. LM35 as Temperature Sensor

When we tell about temperature sensor LM35, we can define that temperature sensor LM35 is electronic component that is used to change the temperature scale into electrical quantities in the form of voltage. LM35 has high quality in accuracy and easy to design as thermometer device. LM35 also has low output impedance and high linearity so that it can be easily connected with a series of special control and does not require further adjustment.

In output, LM35 open analog voltage. LM35 has small analog voltage more than 10mV/ Celsius degree. It is mean that each increase of 1 degree Celsius, LM35 output voltage 10mV. So in design we need conditioning signal to get more high voltage in output. In implementation we need inverting amplifier as signal conditioning. Or we also can use analog to frequency using KA331 schematic as signal conditioning. Please see electronic schematic of KA331 as analog to frequency converter by click link bellow:

According the features of LM35, this sensor has 3 pins with each pin has its own function, among others, pin 1 serves as a source of working voltage of LM35, pin 2 or are being used as the output voltage Vout and pin 3 or used as ground. Please see figure 2. bellow:

Figure 2. Features of LM35

To guide you to use LM35 in your project, you can attention of LM35 characteristic. Here are LM35 characteristic as follow:
  1. It has a temperature sensitivity, with linear scaling factor between voltage and temperature 10 mVolt / º C, so it can be calibrated directly in centigrade.
  2. Having accuracy or calibration accuracy of 0.5 º C at 25 º C.
  3. It has a maximum range of temperatures between -55 º C to +150 º C.
  4. Working at a voltage of 4 to 30 volts.
  5. It has a low current of less than 60 mA.
  6. Having low self-heating (low-heating) of less than 0.1 º C in still air.
  7. Having non-linearity only about ± ¼ º C.
To know more feature and also implementation of sensor LM35 in several schematic, you can see in LM35 datasheet. Here are link to download electronic component sensor LM35.


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