I have to admit that my fancy Extech 407227 spends most of its time in the box for those exact reasons. It takes about 20 minutes to calibrate this piece of junk (and it has an automatic temperature compensation and thermometer electrode... but that needs its own calibration too). Once I finally have it figure out I hate sticking it in my cheese as it does leave dents and holes that later become clogged with wash or whey and develop mold. I didn't want to spend $100 for the flat electrode considering how lame this whole instrument is. During calibration the numbers are inconsistent and fluctuate wildly for several minutes. I dip it in 7.00pH liquid, get a 6.56 reading, shake it a bit and it goes to 7.7pH reading etc. Adjust it to 7.00ph. Wash the liquid off, dip it in 4.01pH liquid and get 3.4pH, shake it, it jumps to 4.6, adjust it to 4.01ph. wash the liquid off, dip it again in the 7.00pH liquid and the reading is now 6.7pH, adjust it again. Now the 4.01liquid shows as 3.9pH and so forth until it stops fluctuating.
By the time this nonsense is done either my cheese has gotten over-acidified or I missed cutting the curd. Even when it's finally balanced, I stick it in the cheese and it reads 5.2pH. I do it again 5 minute laterand it shows 5.6pH, I do it again and it shows 5.1pH. As you can imagine, more often than never, the pH meter guarantees I will mess up and spoil the cheese rather than actually help control its quality. This isn't my meter; my $30 Hanna Checker (Hi98103) acts no difference, only here I have to calculate with a separate thermometer. I feel that the only solution is industrial food lab meter with automated calibration and compensation and those are $1,000+ instruments. Very frustrating