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Problem with calculation

Hi

I have been trying to use the equation:

int Temp;
   Temp = 680*((N-82)/(920-82));
   return Temp;

N=920 - I would expect temp would be 680 and the result is 680 which is correct

But when I tried to use other values below, I keep getting zero.

Then N - 900
Result: 0

adc_result - 700
result:0

adc_result - 500
result:0

adc_result - 300
result:0

adc_result - 100
result:0

I don't understand why this happened.

Arron

Parents

0 Andy Neil over 19 years ago in reply to Chris Wunderlich

"your calculation would indicate you need to change this to floating point maths"

Or just pre-scale N by a suitable factor so that the result is non-zero!
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0 Andy Neil over 19 years ago in reply to Chris Wunderlich

"your calculation would indicate you need to change this to floating point maths"

Or just pre-scale N by a suitable factor so that the result is non-zero!
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0 Andrew Jordan over 19 years ago in reply to Andy Neil

A Neil

Do you have example of using scaling to solve my problem?
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0 Andy Neil over 19 years ago in reply to Andrew Jordan

"Do you have example of using scaling to solve my problem?"

See Drew's reply - use the multiplication by 680 to "scale" the numerator before doing the division!
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