Okay, here is a possible stupid question but I purchased the Milwaukee pH51 meter. It states to store it in a few drops of storage solution or pH7 solution in the protective cap.
Is it simply “few drops” and can I store it with few drops in its case; i.e. laying down horizontally. Will that take the solution off the electrode?
Finally, when would you know the electrode is shot.
Bill
I don’t have that brand of pH meter, but the instructions are similar. I store mine upright with some 7.0 solution in the end cap. Since I use a capful when I calibrate it’s easy to save this for storage.
I think you’ll know when the electrode is getting old when it takes way too long to calibrate. Mine is a year old and recognizes the 7.0 right away, but is taking almost a minute to recognize the 4.0 solution and then longer to calibrate to it. I think this means it’s getting up there in age.
I do the same, but you’ll need to change the storage frequently.
I store my pH 600 with the probe completely submersed in storage solution. I believe that prolongs the life over using 7.0 buffer solution.
Thanks- what should I look for to see if is no longer functioning properly or dried out? Compare it to a test strip?
You should calibrate it every time you’re going to use it. Get some extra 7.0 and 4.0 solutions for this.
This is something I wasn’t aware of. How frequently? Is there some sign that it’s time to change it?
Mine gets little wisps of gunk forming in it (similar to an infected bottle of beer) and the read will be about 6.8-6.9. The green color fades and a slime forms in the cap. Fresh solution and it reads 7.0 without re-calibrating. I think it’s something from the probe contaminating it even though it is kept religiously clean.
Might not affect everyone but it’s good policy to change the storage solution frequently (weekly) if you start to see a drift for no reason.
Here’s a guide to maintaining and storing pH probes.
Does the meter give you any info when it calibrates? (slope and offset)?
If not, as the electrode degrades it will take longer to recognize calibration solution. Also the calibration will not hold as long. For example a few hours into your brew day a (rinsed) probe can be used to measure fresh calibration solution and should be accurate. You can perform this exercise every few months and record the results. As the probe degrades it may measure the calibration solution inaccurately (outside of the probe’s accuracy, not its resolution) and this will get worse with time.
Hi,
Im New to the forum , and new to brewing 
I hope its ok I use your thread for my question, instead of making a new.
I have bought the Milwaukee ph51 pen,
and I’ve been happy with it so far, Ive had it for roughly 4-5 weeks now. But I think Ive done a blunder. Because I did not store it properly in storage solution (I have stored it with cap), and now it has started to act up. Just bounching from pH 4.2 to 7.9 and way back down, never settles on a value or number. Ive tried to change the batteries, and let it sit in plain water for 15-20min. But it won’t give me an exact measurement.
As I said, I have had the pen for 4-5 weeks. Do anyone know if this is fixable? If I get new calibration solution and storage solution. Can I save it? Or is the probe fried?
Hope anyone know what to do 
Best Regards,
Andre Karlsen
Welcome Andre. The first thing I’d try is new calibration solutions, maybe soaking in some storage solution first. If that doesn’t work you probably need a new probe.