01470178| Datasheet

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Standardized R/T Characteristics Standardized R/T characteristics
1 1.1 Introduction Resistance value

The R/T characteristics tabulated in the following have been standardized for the resistance value at 25 C. The actual resistance values of a particular NTC thermistor are obtained by multiplying the ratio R T /R25 (tabulated value) by the resistance value at 25 C (specified in the data sheets). RT R T = -------- R 25 R 25 (1)

Resistance values at intermediate temperatures within the range of the subsequent temperature interval can be calculated by means of the temperature coefficient .

is inserted in the following equation: x 1 1 R T = R T exp --------- ( T x + 273,15 ) 2 --------------------------- ------------------------------ T + 273,15 T + 273,15 x 100 x
RT R Tx Tx T x Resistance value at temperature T Resistance value at the beginning of the relevant temperature interval Temperature in C at the beginning of the relevant temperature interval Temperature of interest in C (Tx < T < Tx+1) Temperature coefficient at temperature Tx (2)

Example: Given: Curve 1006 R 25 = 4,7 k 5 = 4,4 Resistance at 7 C (R 7)

Unknown:

a) Calculation of the resistance value at the beginning of the relevant temperature interval (T x = 5 C): R T = R 5 = 2,2739 4,7 k = 10,6873 k
x

b) Substituting this value into equation (2) yields:

5 1 1 R 7 = R 5 exp --------- ( 5 + 273,15 ) 2 --------------------------- --------------------------- 7 + 273,15 5 + 273,15 100
4,41 1 R 7 = 10,6873 k exp --------- 278,15 2 ----------------- ----------------- 280,15 278,15 100 R 7 = 10,6873 k exp [ 0,08737 ] = 10,6873 0,9163 R 7 = 9,7932 k

147 05/02