Enter the resistance at two different temperatures into the calculator to determine the B value, a parameter that characterizes the temperature dependence of the resistance of a thermistor.

B Value Formula

The following formula is used to calculate the B value. 

B = (T1 * T2) / (ln(R1 / R2) * (1/T1 - 1/T2))

Variables:

  • B is the B value (Kelvin)
  • R1 is the resistance at temperature T1 (ohms)
  • T1 is the temperature T1 (Kelvin)
  • R2 is the resistance at temperature T2 (ohms)
  • T2 is the temperature T2 (Kelvin)

To calculate the B value, you need to measure the resistance of the thermistor at two different known temperatures. Then, apply the formula where B is the B value, R1 is the resistance at temperature T1, T1 is the first temperature, R2 is the resistance at temperature T2, and T2 is the second temperature.

What is a B Value?

The B value is a constant that indicates the temperature sensitivity of a thermistor. It is derived from the Steinhart-Hart equation, which is a model that describes how the resistance of a thermistor changes with temperature. The B value is used in various applications, including temperature sensing and control systems, to convert the resistance of a thermistor into a temperature reading.

How to Calculate B Value?

The following steps outline how to calculate the B Value.

  1. First, measure the resistance of the thermistor at a known temperature T1 (R1).
  2. Next, measure the resistance of the thermistor at a second known temperature T2 (R2).
  3. Use the formula B = (T1 * T2) / (ln(R1 / R2) * (1/T1 – 1/T2)) to calculate the B value.
  4. Finally, enter the measured values into the calculator above to verify the B value.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Resistance at temperature T1 (R1) = 10000 ohms

Temperature T1 = 298.15 Kelvin (25°C)

Resistance at temperature T2 (R2) = 25000 ohms

Temperature T2 = 353.15 Kelvin (80°C)