B25-85 refers to the B value of a thermistor, specifically calculated based on resistance measurements at 25°C and 85°C.
Understanding the B Value
The B value (also sometimes represented as β) is a parameter used to characterize the resistance-temperature relationship of a Negative Temperature Coefficient (NTC) thermistor. It indicates how much the resistance of the thermistor changes with temperature. A higher B value signifies a more significant change in resistance for a given temperature change, making the thermistor more sensitive.
B25/85 Calculation Context
The notation "B25/85" or "B25-85" specifies that the B value was determined using resistance measurements taken at 25°C (298.15 K) and 85°C (358.15 K). This is a standard way to define the temperature range used for the calculation.
Calculation Formula
While the exact B value is a characteristic provided by the manufacturer, it's calculated using the following (or similar) formula:
B25/85 = ln(R25/R85) / (1/T25 - 1/T85)
Where:
- R25 is the resistance at 25°C (298.15 K)
- R85 is the resistance at 85°C (358.15 K)
- T25 is 25°C converted to Kelvin (298.15 K)
- T85 is 85°C converted to Kelvin (358.15 K)
- ln is the natural logarithm
Significance
The B25/85 value is crucial for:
- Thermistor Selection: Choosing the right thermistor for a specific application based on the desired temperature sensitivity.
- Circuit Design: Designing the circuitry to accurately interpret the thermistor's resistance and translate it into a temperature reading.
- Temperature Measurement Accuracy: Ensuring accurate temperature measurements within the specified temperature range.
In summary, B25-85 is the B value of a thermistor calculated using resistance measurements at 25°C and 85°C, indicating the temperature sensitivity within that range.
