Home Brew Forums > Home Brewing Beer > Brew Science > pH Meter Temperature Compensation
Reply
 
Thread Tools
Old 05-07-2013, 08:20 PM   #11
ajdelange
HBT_LIFETIMESUPPORTER.png
Feedback Score: 0 reviews
Recipes 
 
Join Date: Aug 2010
Location: McLean/Ogden, Virginia/Quebec
Posts: 7,901
Liked 1079 Times on 845 Posts
Likes Given: 33

Default

I don't see anything about calibration in that statement and I don't see any calibration parameters in their formula whatever you put into it.

Fortunately, there is only one requirement for success with the formulas at http://wetnewf.org/pdfs/ph-meter-calibration.html and that is that the reading, however it is scaled or offset, be a linear function of the voltage produced by the electrode. If you get actual millivolts the electrode voltage is
E = Eo - s*(R*T/F)(pH(T) - pHi)
with Eo being a few mV depending on the electrodes aging and s a number close to (a bit less than) 1 again depending on age and RT/F = 58.167 mV/pH at 293.15 K (20 C). pHi is assumed to be 7 (though it actually isn't but should be close to it for most electrodes). The formula you are looking at assumes this but does not incorporate the other two calibration parameters :Eo and s. As such it can only produce approximate answers.

If you are going to write code I don't see much point in using an approximate formula when a much more robust one is readily available to you. Yes, you will have to also write code (doesn't have to be on the micro computer) that takes two mV readings (or 2 scaled mV readings) and two temperature readings (one temperature/mV pair for each buffer) and solves for s and Eo but that isn't rocket science. The formulas are there with the others.


ajdelange is offline
 
Reply With Quote
Reply


Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
PH meter and temperature Yooper Brew Science 16 01-06-2012 09:37 PM
Refractometer Compensation Sudz Equipment/Sanitation 1 12-28-2011 03:18 PM
Temerature compensation for volume Bru General Beer Discussion 3 10-20-2011 02:04 PM
Temperature Loss Compensation chaydaw All Grain & Partial Mash Brewing 14 02-24-2011 03:57 PM
Elevation compensation benbradford General Techniques 12 03-26-2010 08:54 PM


Forum Jump

Newest Threads

LATEST SPONSOR DEALS