NTC-Lookup-Table-Seite auf Deutsch
NTC-Lookup-Table-Seite auf Deutsch

NTC Voltage Divider Lookuptable

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Given a voltage divider R1 connected to VCC and a NTC connected to ground.

Calculation is done in two steps. First you have to enter three pairs of temperature/resistance. From these, the coefficients for the Steinhart Hart formula are computed.

A fast microcontroller might calculate the temperature according to the coefficients in real time. More oftenly, you'll need only few discrete values that can be called from a lookup table more efficiently. Output is formatted like <Temp>,<Value>,<Voltage> where Temp is the temperature in degrees celsius, Value is the AD converter value and Voltage is the actual measured voltage.

Notice:

Until now, I only use NTCs from Vishay who specify the coefficients for the Steinhart Hart equation directly. Therefore, the form for the Vishay-version is more sophisticated.

T1[°C]

RT1[Ω]

T2[°C]

RT2[Ω]

T3[°C]

RT3[Ω]

R1[Ω]

Varef [V]

A/D res


The Steinhart Hart Formula

is used to calculate the NTC resistance for a given temperature.

1/T=A+B*ln(r)+D*ln(r)^3

A

B

D


Single Values

Value T(R)

RNTC [Ω]

T [°C]

V [V]

A/D

Value R(T)

T [°C]

RNTC [Ω]

V [V]

A/D

Value T(AD)

A/D

RNTC [Ω]

T [°C]

V [V]


Tables

Step
T von [°C]

T bis [°C]

Step

© 2007-2013 Robert Loos

All results without warranty!