Assuming it's linear...

TDS =3D (2500-30)/(6500-400)F + C
Using any point, I get C =3D -132, so ...

TDS =3D 0.4049 * F -132

Cheers,
-Neil




On 8/22/2014 11:48 AM, Ravi wrote:
> Hello All,
>
> I hope that I have the right tag. I am a bit rusty and hope that some
> one would point me in the right direction.
>
> I am designing a TDS meter.
>
> For a TDS of 2500, I get a frequency of 6500 Hz and for a TDS of 30, I
> get a frequency of 400 Hz.
>
> My 2 points of calibration are those below.
>
> 6500 Hz - 2500 TDS
> 400 Hz - 30 TDS
>
> I need a formula to calculate the intermediate values based on the
> incoming frequency.
>
> Thanks in advance
>
> Cheers
>
> Ravi
>

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