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What's the need of the Dissipation factor (mW/°C) #3
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Hi there,
the Steinhart-Hart is for NTC thermistors specifically, which always experience a bit of self-heating.
The dissipation factor usually takes the ambient temperature into account. The constant I used is just an approximation for the average room temperature if I remember correctly.
K is just the ratio of change in power dissipation and the resultant increase in the body temperature of the thermistor itself. So for larger values of K the resulting temperature gets lowered depending on the power flowing through the thermistor.
Just glancing at the data sheet you linked to, the manufacturer claims less than 0.01 °C self-heating, maybe that’s why they don’t need a dissipation factor.
Cheers
Andy
… On 20. Feb 2021, at 00:33, Pierrot ***@***.***> wrote:
Dear findie
First, thanks for that nice library.
I need to make working the SF-110 sensor <https://www.apogeeinstruments.com/content/SF-110-manual.pdf> from Apogee and I observed on page 10, they do not use a dissipation factor.
I wonder why you consider that here <https://github.com/fiendie/SteinhartHart/blob/master/SteinhartHart.h#L32>
and if you can clarify me this section <https://github.com/fiendie/SteinhartHart/blob/master/SteinhartHart.cpp#L43>.
I have some difficulties to understand the role of the K and the following calculation with the consideration of the voltage
getTempKelvin = TempKelvin - voltage * voltage / (K * _resistance)
You support will be greatly appreciate.
Thanks
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Andy, I appreciate your SH library as I'm adapting it for my project; thanks. In the spirit of constructive feedback, and perhaps I am just dense, but I can't see that self-heating correction approach you apply in the library is valid in concept nor approach.
As I see it, The main problem is that K is in mW/deg C yet the SHH equation is returning deg Kelvin so you are subtracting a correction in deg C from a deg K value. Also, V^2/R comes out in W, yet the dissipation factor is mW/degC. If I've completely mis-understood this, please correct me. Cheers! |
Dear findie
First, thanks for that nice library.
I need to make working the SF-110 sensor from Apogee and I observed on page 10, they do not use a dissipation factor.
I wonder why you consider that here
and if you can clarify me this section.
I have some difficulties to understand the role of the K and the following calculation with the consideration of the voltage
getTempKelvin = TempKelvin - voltage * voltage / (K * _resistance)
You support will be greatly appreciate.
Thanks
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