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,