#Arduino thermometer series

From kelvin, the temperature values can be easily converted to either Celsius or Fahrenheit by using the below equations. Then this resistor value can be applied in the Steinhart–Hart beta parameter equation which gives the temperate value in kelvin.

#Arduino thermometer series

V – Total voltage across the series resistor R T – Instantaneous resistance value of the thermistor V RT = V * R T/R S + R T by rearranging this equation the expression for RT can be obtained as, R T = V RT * Rs / (V – V RT). So, using the voltage division formula, the instantaneous value of the resistance is calculated from the voltage measured across the thermistor. Hence the voltage across the thermistor will be proportional as per the voltage division of series resistor circuits. In both the above circuits, the thermistor is in series with a resistor of a fixed value. It also has a DO-LED which works inverse to the digital output LED ON when the output is LOW and LED OFF when output is HIGH. It gives a HIGH state output if the temperature is below the threshold and the output switch to LOW when the temperature is above the threshold. The only difference of the module is it has an additional digital output with a threshold setting that can be adjusted by the potentiometer. It also has the analog input of the Arduino connected across the NTC thermistor with a 10k series resistor and connected across a 5V supply.

In a thermistor module, the analog output of the module is connected to the analog pin of the Arduino which has the same circuit as the above one. The analog input of the Arduino is connected across the thermistor, so the resistance of the thermistor can be calculated from the voltage drop measured across it.

In the below standalone circuit, a 50K thermistor is connected in series with a 10k resistor, and a 5V supply is connected across the series circuit. The temperature value in kelvin for the respective resistance (R) of NTC thermistor, T = 1 / (1/To + 1/B In(R/Ro))Ī thermistor module or a standalone thermistor both can be used to measure the temperature. R o – Nominal Resistance, resistance at temperature T 0 is 25 ☌ or 298.15K R – Measured resistance of the thermistor T o – Nominal Temperature, 25 ☌ or 298.15 K

Steinhart–Hart β parameter equation, 1/T = 1/To + 1/B In(R/Ro) It can obtain the temperature values that are approximately equal to the actual values from the instantaneous resistance of the thermistor. It is considered the best mathematical expression to obtain the resistance vs temperature characteristic of an NTC thermistor. In code, the temperature of the NTC thermistor is calculated by using the Steinhart–Hart equation. This rate of change of resistance versus temperature curve is indicated by a constant value called Beta value or Beta coefficient. As it is nonlinear the temperature-resistance graph does not have a straight line. That is the resistance value decreases if the temperature of the thermistor is increased and it increases if the temperature is decreased. * * Created by ArduinoGetStarted.NTC (Negative Temperature Coefficient) thermistor has a characteristic of non-linear inverse varying resistance with respect to the temperature change.