SAM-1 stability test

[motobrewer]

I calibrated just before, but I could have let the probe sit longer before accepting the cal. I probably let it sit for 45 seconds. Also I probably should have let the buffer come down to room temp before starting.

 

[ajdelange]

Yes, for a stability check it doesn't hurt to let it go a couple of minutes. Looks good as is though.

 

[motobrewer]

also I tried to put the corrected pH using your formula. This is what I entered in excel:

=((1617.3/D1)-9.2852+(0.033311*D1)-(2.3211*(EXP(1)^(-5*D1^2))))

where D1 is temp in kelvin. For D1=297.15 (75.2F) I get a result of 6.056.

what am I doing wrong?

 

[ajdelange]

The formula is

pH 4: 1617.3/K -9.2852 + 0.033311*K - 2.3211E-5*K*K

Type = 1617.3/D1 -9.2852 + 0.033311*D1 - 2.3211E-5*D1^2

and you should get the right answer. IOW E is the symbol for the exponent part of a floating point number, not the base of natural logarithms. I know it had e in the Sticky. I've changed it.

 

[motobrewer]

Got it. Thanks!

 

[motobrewer]

I'll probably mess with it again but I am a little annoyed by the drift. Altho I have absolutely no baseline.

I did take a reading of the fast ferment test of a helles I brewed (1.049 OG). FFT finished at 1.010 with a pH of 3.99. The actual beer is still fermenting (7 days in primary so far), it's at 1.015 with a pH of 4.40. I did try to decarb the sample as best as possible by stir plating then pouring back and forth.