This example demonstrates how to measure temperature using a 10k NTC thermistor with a B-parameter of 3950. The thermistor forms a voltage divider with a 10kΩ resistor, and the Arduino reads the midpoint voltage. Using the Steinhart-Hart equation, the thermistor’s resistance is converted into temperature in:

• Kelvin (K)
• Celsius (°C)
• Fahrenheit (°F)

• NTC Thermistor: Its resistance decreases as temperature rises. Using the B-parameter (3950), the resistance is mapped to temperature using Steinhart-Hart.
• Voltage Divider: The thermistor and a 10kΩ resistor form a divider. Arduino measures the midpoint voltage to compute resistance.
• Temperature Calculation: The Steinhart-Hart equation computes temperature in Kelvin, then converted to °C and °F.

• 10k NTC thermistor
• 10kΩ resistor (voltage divider)
• Arduino Uno

• Thermistor → 5V
• Thermistor → junction with 10kΩ resistor
• Junction → A1 (ADC1)
• 10kΩ resistor → GND

/*
 * © 2024 Copyright Peter I. Dunne, all rights reserved.
 * Prepared for educational use.
 * The ADC is 10 bit, this is of relatively low accuracy, use professional test equipment for accuracy.
 * Released under the Mozilla Public License
 * Arduino UNO with 10k NTC Thermistor and B-parameter of 3950
 * Measures temperature and converts it to Kelvin, Celsius, and Fahrenheit.
 */

const int thermistorPin = A0;
const int referenceResistor = 10000;
const float B_coefficient = 3950;
const float nominalTemperature = 298.15; // 25°C in Kelvin
const float nominalResistance = 10000;
const float VRef = 5.0;
const int maxADCValue = 1023;

void setup() {
    Serial.begin(115200);
    Serial.println("Arduino NTC temperature measurement, by Peter Ivan Dunne, ©2024, all rights reserved");
    Serial.println("Released under the Mozilla Public License");
    Serial.println("https://jazenga.com/educational");
}

void loop() {
    int adcValue = analogRead(thermistorPin);
    float voltage = (adcValue / float(maxADCValue)) * VRef;

    float thermistorResistance = referenceResistor * ((VRef / voltage) - 1);

    float steinhart;
    steinhart = thermistorResistance / nominalResistance;
    steinhart = log(steinhart);
    steinhart /= B_coefficient;
    steinhart += 1.0 / nominalTemperature;
    steinhart = 1.0 / steinhart;

    float temperatureC = steinhart - 273.15;
    float temperatureF = (temperatureC * 9.0 / 5.0) + 32.0;

    Serial.print("Temperature: ");
    Serial.print(steinhart, 2);
    Serial.print(" K, ");
    Serial.print(temperatureC, 2);
    Serial.print(" °C, ");
    Serial.print(temperatureF, 2);
    Serial.println(" °F");

    delay(1000);
}

• ADC Reading: Arduino reads 0–1023 proportional to the divider voltage.
• Thermistor Resistance: thermistorResistance = referenceResistor * ((VRef / voltage) - 1);
• Steinhart-Hart Equation: Temperature is computed in Kelvin using:

  steinhart = thermistorResistance / nominalResistance;
  steinhart = log(steinhart);
  steinhart /= B_coefficient;
  steinhart += 1.0 / nominalTemperature;
  steinhart = 1.0 / steinhart;

• Celsius & Fahrenheit:

  temperatureC = steinhart - 273.15;
  temperatureF = (temperatureC * 9.0 / 5.0) + 32.0;