The Beta (β) value of a thermistor is an indicator of the slope of the resistance/temperature curve characteristic and is calculated by measuring the resistance values of the device, under zero power conditions, at two temperature points. The resistance values are then entered into the following equation:
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β = Ln (R1/R2)/(1/T1-1/T2) |
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where T1 = 273.15 K (0 °C) and T2 = 323.15 K (50 °C) |
The β value is not a true material constant and is temperature dependent. However, it is useful for calculating resistance values over a narrow temperature range. Depending on the temperature span, errors associated with Beta calculations range from 0.01 °C error over a 10 °C span to 0.3 °C error over a 50 °C span. Typically, the Beta tolerance, which depends on the ability of the manufacturer to control its process, can be expressed in ± K or more commonly in ± % percent of Beta.
See also: Beta / Resistance Ratios Table
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