Sounds like the innards got wet; mine's real finicky that way (I dropped it into a batch of nutes for like a millisecond before I snached it out and dried it off, but the readings would swing wildly.) I took the battery cap out, dried off all the batteries and let everything dry out in front of a fan blowing warm dry fan for a couple days. Reassembled it and it worked. Needed recalibrating, but once I did that it's held to +-.1 for months now. So, no, you shouldn't have to recalibrate it often at all.

If your tap water is consistent pH you can check calbration, quick and dirty, by sampling your tapwater, provided there's some ppm to it. I don't bother with calibration solution too often any more, like I said it's held steady since I dried it out. I check it against another meter frequently, though.

And don't store the thing in distilled or deionized water. Or calibration solution. I just keep mine, cap off, in a little juice glass with .5" or so of vinegar, diluted with hard water to pH 3.5 or so (not critical). My cap leaked out all my storage solution, so that didn't work out for me.

Don't know if my storage method is approved by anybody, but my meter's still working fine. :icon506: It's just real convenient for me to use like that.

Good luck! Let us know if you can "heal" it.

HTH, Hermie

P.S. I try not to get any part of the meter wet except the pH probe itself. They're NOT waterproof! If you use the cap I would keep the pen in an upright position to keep the liquid at the bottom.
DreadedHermie Reviewed by DreadedHermie on . Questions about PH pen... Whats up... Just bought a new Milwaukee PH 600 pen and I have a couple questions. Since this is my first pen... I calibrated it to 7.0 with the solution it came with. Tested my res with it fine. I washed it and put a small piece of sponge in the cap with the storage solution. The next day now the PH was crazy on the pen... My question is, Does it need to be calibrated before every use?? Also did I use the storage solution correctly? It didnt come with any instructions really.. Rating: 5