SOP for calibration and use of DO meters

[caedus]

Hey there. Just got my DO meter in the mail, and am now playing with it. I figured I would run some questions by you guys and see how you guys use and calibrate them.

I have heard of two ways to make a zero-oxygen solution:
1. Bakers yeast and water
2. 5% SMB solution

Both are cheap (compared to a $20 bottle of Zero solution) and easy to produce, but I wanted to see what you guys were doing to calibrate.

I know user mchrispen mentioned using stainless steel cups to pull and quickly cool samples, but I was curious as to what Bryan and the others with DO meters were doing to cool samples prior to taking a reading.

I would like to make a quick Standard Operating Procedure for taking such readings, and keep them posted for the future to ensure accuracy and that everyone is on the right page when it comes to measurement.

[mchrispen]

The SMB would at least prevent any organic solids from fouling the meter... just saying.

[caedus]

I definitely prefer the SMB, however most of the guides I am seeing call for Cobalt chloride to quicken the interaction between sulfite and oxygen, and I don't have nay of that laying around.

I am running a test now of 5% by weight SMB solution and seeing how it turns out.

[mchrispen]

Also - remember that the solution in the meter consumes O2 as well... so don't leave it for an extended time beyond stability.

[Bilsch]

You will be surprised how well yeast works for ripping the oxygen out of solution.

[Bryan R]

Tech, and Brandon have both done the zero cal, while I did not. Our readings were * I think* within .1 of each other.

I always turn mine on, leave the cap on and let it sit until it shuts off. ( you should see a little blinking icon on the bottom right of the screen now).
I then turn it on again, and allow the reading to stabilize.
I then hit cal, and you will see 101.7, let it self cal.
Then grab your sample and make sure there are no bubbles on the membrane.
Get your reading.

[Techbrau]

I tried taking measurements of finished beer that had a DO content of approximately 0.4 with and without zero calibrating my meter. I got the same reading.