Temperature Sensor LM35

The LM35 Temperature Sensor is a high-precision integrated-circuit temperature sensor designed for accurate temperature measurements. It provides a voltage output that is directly proportional to temperature in degrees Celsius. The LM35 is highly valued for its ease of use, cost-effectiveness, and excellent linearity, with a typical accuracy of ±¼°C at room temperature and ±¾°C over a wide temperature range from -55°C to 150°C.

Features:

• Centigrade Calibration: The LM35 is calibrated in Celsius, making it ideal for applications where temperature needs to be directly measured in degrees Celsius.

• Cost-Effective Wafer-Level Calibration: It’s affordable due to its calibration at the wafer level.

• Linear Scale Factor: The sensor has a linear output of 10 mV per degree Celsius, making temperature readings straightforward to interpret.

• Low Self-Heating: The LM35 generates minimal self-heating (just 0.08°C in still air), which ensures accuracy.

• No External Calibration Needed: The LM35 is pre-calibrated, so it doesn't require additional calibration.

• Single Power Supply Compatibility: It operates with a single power supply, adding versatility to its use.

Applications:

• Climate Control Systems: Used in HVAC systems to regulate indoor temperatures.

• Industrial Automation: Helps monitor machinery temperature, preventing overheating.

• Weather Stations: Measures temperature in meteorological stations.

• Medical Devices: Found in incubators and fever monitoring systems.

• Home Appliances: Ensures proper temperature regulation in appliances like refrigerators and ovens.

• Environmental Monitoring: Measures temperature changes in ecosystems.

• Automotive: Monitors engine temperatures in vehicles.

• Energy Efficiency: Helps regulate systems in energy-efficient buildings.

• Food Processing: Ensures proper temperature during food processing.

• Scientific Research: Used in laboratories for temperature-sensitive experiments.

• Agriculture: Applied in greenhouse temperature monitoring.

Code for Arduino Integration:

#define sensorPin A0

void setup() {
  // Initialize serial communication at 9600 baud rate
  Serial.begin(9600);
}

void loop() {
  // Read the analog voltage from the LM35 sensor
  int rawValue = analogRead(sensorPin);
  
  // Convert raw reading to voltage (0-5V)
  float voltage = (rawValue / 1023.0) * 5.0;
  
  // Convert voltage to temperature in Celsius
  float temperatureC = (voltage - 0.5) * 100.0;
  
  // Print temperature in Celsius
  Serial.print("Temperature: ");
  Serial.print(temperatureC);
  Serial.print("\xC2\xB0C | ");
  
  // Convert Celsius to Fahrenheit
  float temperatureF = (temperatureC * 9.0 / 5.0) + 32.0;
  Serial.print(temperatureF);
  Serial.print("\xC2\xB0F");
  
  // Print a newline for better readability
  Serial.println();
  
  // Wait for a second before the next reading
  delay(1000);
}

Circuit:

• Connect the LM35's VCC pin to the 5V pin of the Arduino.

• Connect the OUT pin to the analog pin A0.

• Connect the GND pin to the ground.

Technical Details:

• Operational Voltage: 4 – 30V

• Output Voltage: -1V to 6V

• Output Current: 10mA

• Operating Temperature: -55°C to 150°C

• Accuracy: ±0.5°C at 25°C

Comparisons with NTC Thermistors:

• LM35: Provides direct linear voltage output, is pre-calibrated, and requires no further calibration. Ideal for precise temperature measurements in Celsius.

• NTC Thermistors: Have non-linear characteristics, requiring calibration. While they are often cheaper, they don’t provide a direct output like the LM35 and are less straightforward to use in temperature measurements.