LM35 temperature sensor is an electronic component that has a function to turn the temperature scale into electrical quantities in the form of voltage. LM35 temperature sensor used in this study is an electronic component electronics manufactured by National Semiconductor. LM35 has high accuracy and ease of design when compared with the other temperature sensor, LM35 also has a low output impedance and high linearity so that it can be easily connected to a special control circuit and does not require further adjustment.
Although the voltage sensor can reach 30 volts but given kesensor is at 5 volts, so it can be used with a single power supply with the provision that the LM35 only requires a current of 60 uA it meant LM35 has the ability to generate heat (self-heating) of the sensor that may cause low readings of less than 0.5 ° C at a temperature of 25ºC.
The image above shows the shape of LM35 looked forward and looked down. 3 pin LM35 addressing the function of each pin them, pin 1 serves as a source of working voltage of LM35, pin 2 or being used as a voltage output or Vout with working range from 0 volts up to 1.5 volts with an operating voltage of LM35 sensor which can used between 4 Volts to 30 Volts. The sensor output will rise by 10 mV per degrees centigrade in order to obtain the following equation:
VLM35 = 10 mV / oC
Pictured above right is a schematic drawing of a basic circuit-DZ LM35 temperature sensor. The circuit is very simple and practical. Vout is a scalable sensor output voltage linearly with the measured temperature, which is 10 millivolts per 1 degree Celsius. So if Vout = 530mV, then the measured temperature is 53 degrees Celsius. And if Vout = 320mV, then the measured temperature is 32 degrees Celsius. The output voltage can be directly fed as input to the signal conditioning circuit such as the operational amplifier circuit and filter circuits, or other circuits such as voltage comparator circuit and circuit Analog-to-Digital Converter.
The basic circuit enough to merely experiment or for applications that do not require a perfect measurement accuracy. But not for a real application. Evident from the experiments that I have done, sensor output voltage is not yet stable. At the temperature conditions are relatively similar, if my supply voltage fluctuates (I raise or lower), then Vout also changes. Indeed, the logic of this seems true, but for the instrumentation it is not allowed.
Compared with the level of precision, the degree of accuracy of measuring instruments more prominent since the measuring instrument should be used as a benchmark for its users. If the value is changeable relative to the condition that there is no change, then the measuring tool so it can not be used.