The main parameters of thermistor: Resistance and B value, Is the user product selection major consideration. Yaxun electronic analysis thermistor parameters are as follows:
B value is the thermal coefficient of negative temperature coefficient thermistor. It is defined as the difference between the natural logarithms of the zero-power resistance values at two temperatures And the ratio of the two temperature reciprocals.
That is, the thermistor chip (a semiconductor ceramic) after high temperature sintering, Forming a material having a specific resistivity. There is only one B value for each formulation and sintering temperature, So called material constant.
The B value can be calculated by measuring the resistance at 25 degrees Celsius and 50 degrees Celsius (or 85 degrees Celsius). B value and the product temperature coefficient of positive correlation, In other words, the greater the B value, The greater the temperature coefficient of resistance.
Temperature coefficient refers to the temperature for every 1 degree increase, The rate of change in resistance. The B value can be converted to a resistance temperature coefficient using the following formula:
Resistance temperature coefficient = B value / T ^ 2 (T is the absolute temperature value to be converted)  NTC thermistor B value is generally between 2000K-6000K, Can not simply say that the B value is the bigger the better or the smaller the better, Depends on where you use. In general, As a temperature measurement, Temperature compensation and suppression of surge resistance with the product, Under the same conditions, the value of B is good. Because as the temperature changes, B value of the larger changes in its resistance value of the product, That is more sensitive.
NTC thermistor B value formula:B = T1T2 Ln (RT1 / RT2) / (T2-T1) Which B: NTC thermistor B value, provided by the manufacturer; RT1, RT2: thermistor resistance at temperature T1, T2, respectively; T1, T2: absolute temperature scale. V

NTC thermistor B value formula.
NTC thermistor resistance calculation formula: Rt = R * EXP (B * (1 / T1-1 / T2)
Description:
1, Rt is the thermistor in the T1 temperature resistance;
2, R is the nominal resistance of the thermistor at T2 ambient temperature;
3, B value is an important parameter of thermistor;
4, EXP is the nth power of e;
5, where T1 and T2 refer to the K-degree Kelvin temperature, K = 273.15 (absolute temperature) + degrees Celsius;

Or expressed as r = R * EXP (B * (1 / t-1 / T)
Description: 1, r is the thermistor resistance at t temperature;
  2, is the thermistor at T at room temperature, the nominal resistance;
3, B value is an important parameter of thermistor;
4, EXP is the nth power of e;
5, where t and T refer to the K-degree Kelvin temperature, K = 273.15 (absolute temperature) + degrees Celsius;

The NTC resistance values for two different B values are (for example, 3435 and 3950):
R = 10 * EXP (3435 (1 / t-1 / 298.15))
R = 10 * EXP (3950 (1 / T - 1 / 298.15))
Assuming that the two NTC resistors have the same resistance,
3435 (1 / t - 0.003354) = 3950 (1 / T - 0.003354)
Solving the equation can obtain two kinds of B value temperature conversion relations:
NTC resistance value of 3950 B to 3435 temperature value conversion algorithm:
T = 3950 / (3435 / t + 1.727) = 3950 t / (1.727 t + 3435)
Among them: Temperature unit: ℃, (25 degrees above 3950 value is high)
  NTC resistance value of 3950 B to 3435 temperature value conversion algorithm:
T = 3435 / (3950 / T-1.727) = 3435T / (3950-1.727T)
Among them: temperature unit: ℃, (25 degrees above 3435 value is low

Yaxun electronic product parameters are as follows:
    MF5A-502F-3470 models of the thermistor
     MF5A - type epoxy package
     502 - Nominal resistance at room temperature 25 degrees is 5K
     F - Tolerance is (accuracy) ± 1%
     3470 - NTC thermistor with B value of 3470K
RT = 5000 * EXP (3470 * (1 / T1-1 / (273.15 + 25)), R = 5000, T2 = 273.15 + 25, B = 3470,