Extech DO Meter, a million questions

[Bilsch]

I'm following your experiments with great interest.
Good work.

[Brody]

Thanks, I may even beat a batch up (if it's going to be blown in a night by drunk people, screw it) and revert it to the standard AHA style procedures and put the triangle test everyone's been on about to test.

First step though is auditing my own process regarding mashing in and lautering with my bag.

[Owenbräu]

I've found the meter to only be useful when testing my system with plain water. It lets me simulate my process and see when and where I am picking up O2 without ruining the membranes and also without the grains acting to mitigate DO infusions. Even though it claims to be safe to 122F, I have yet to put it in the mash, heat it up, then not get bubbles forming inside the cap after it cools back down. Between stretching the membrane and sucking in air as it cools, I've essentially given up on trying to use the meter in the mash. If you are playing around with acid rests at 100F, then it works ok.

FWIW, I tried the 5% SMB calibration, and the results were variable at best. It will do it, but I don't think it likes it much.

[Brody]

What I've been doing is pulling a sample and cooling it. Which I'm sure would add some O2 by itself.

[Weizenberg]

These meters are not precise enough to reliably test DO to the accuracy needed for establishing the low concentrations of DO.

For this you need to spend $700 upwards (the optical ones many breweries use cost about $10,000). However it can tell you whether you have relative ingress of O2 (does my reading rise?) and it can tell whether one is in an acceptable ballpark.

Most importantly though: DO meters are irreplaceable when aerating wort.

For most of the primitive process control we need, they do fine and give a good price value ratio. They can also highlight gross errors in the process, just don't expect to detect 0.1 mgl reliably. That could show up as 0.1 or 0.5.

If you read the manual carefully you will see a section where they mention that leaving the electrode immersed for too long, the electrode itself will remove oxygen.

Best

[Brody]

[Bilsch]

That's what I see as well.. Gradual steady drop then stabilize for a few seconds then gradual steady climb. I use the reading from the moment of stabilization.

[Brody]

[Brody]

[Bilsch]

I will almost always see something like; 0.27,0.26,0.25,0.25,0.25,0.26,0.27,0.28 etc but only if the meter and the sample are motionless.