I'm trying to work out how the get the answer of this formula,,


https://www.jameco.com/Jameco/workshop/TechTip/temperature-measurement-ntc-thermistors.html

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Where they get the example answer of 0.003527 ,, it's the formula I'm not understanding, the double brackets...

Do I work out 1023÷ 366, then subtract 1, log it and multiply it by the fractions total?

If you can show me how to work it out thanks ..

 

hi D,
Is this clip the section you are referring too:

For example, assume a thermistor voltage divider circuit is connected to a 10 bit ADC. The beta constant for the thermistor is 3380, the thermistor resistance (R0) at 25°C is 10K ohms, and the ADC returns a value 366.

1/T = 1/298.15 + 1/3380 * ln((1023 / 366) - 1 )
1/T = 0.003527
T = 283.52K – 273.15K = 10.37°C

 

Yes Eric

 

hi Dave,
An acronym for the solving order of an equation is BODMAS
Brackets, Of, Division, Multi, Add, Subtraction.
You should solve the deepest nested brackets first and then work out solving the inner most brackets as you go.
Does that help you.?
E

 

No it doesn't help me, i need to see it worked out in stages please, i keep getting the wrong result Eric.. If someone can show the steps and results thanks..

I tried 1023/366 then subtracted 1, i get 1.795, then I'm stuck!!

 

hi Dave,
This what Microsoft Math Calc shows.
I have also evaluated the 'ln' as a separate equation to show the steps.

Added to show this intermediate step.

 

hi,
Yes the natural ln value is 0.585 as you say.
You then multi that value by 1/3380 , which is 0.000296 * 0.585 =0.000173

Now add 1/298.15 , which is 0.00354 so that total is 0.00354 + 0.000173 = 0.003527


E

 

BINGO!, i kept adding the two fractions first, then multiplying by the Log,

,i realise now you add the first one ( 1/298.15) only. Thankyou.. D

 

hi Dave,
This is a clip of the free download Microsoft Maths program for Win 10, very handy for solving lots of equations.
You can use the PC keyboard or the Mobile Pad.
E