Apogee TS-100 El manual del propietario descargar pdf (Pagina 12)

12

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An excitation voltage of 2.5 V DC is recommended to minimize self-heating and current drain, while still

maintaining adequate measurement sensitivity (mV output from thermistor per C). However, other

excitation voltages can be used. Decreasing the excitation voltage will decrease self-heating and current

drain, but will also decrease thermistor measurement sensitivity. Increasing the excitation voltage will

increase thermistor measurement sensitivity, but will also increase self-heating and current drain.

Conversion of Thermistor Resistance to Temperature:

The thermistor is a resistive element, where resistance changes with temperature. Thermistor resistance

, in ) is measured with a half-bridge measurement, requiring a known excitation voltage input (V

)

and a measurement of output voltage (V

OUT













 1

24900R

OUT

(1)

where 24900 is the resistance of the bridge resistor in . From resistance, temperature (T



, in Kelvin) is

calculated with the Steinhart-Hart equation and thermistor specific coefficients:

))R(ln(C)Rln(BA





(2)

where A = 1.129241 x 10

-3

, B = 2.341077 x 10

-4

, and C = 8.775468 x 10

-8

(Steinhart-Hart coefficients).

If desired, measured temperature in Kelvin can be converted to Celsius (T

15.273TT



. (3)

PRT:

1 2 ... 7 8 9 10 11 12 13 14 15 16 17 18 19

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Apogee TS-100 El manual del propietario Pagina 12

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